US20180136162A1 - Electrochemical sensors for testing water - Google Patents
Electrochemical sensors for testing water Download PDFInfo
- Publication number
- US20180136162A1 US20180136162A1 US15/858,498 US201715858498A US2018136162A1 US 20180136162 A1 US20180136162 A1 US 20180136162A1 US 201715858498 A US201715858498 A US 201715858498A US 2018136162 A1 US2018136162 A1 US 2018136162A1
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- reagent
- working electrode
- electrochemical sensor
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims description 77
- 229910001868 water Inorganic materials 0.000 title claims description 71
- 238000012360 testing method Methods 0.000 title description 4
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 132
- 239000000203 mixture Substances 0.000 claims abstract description 100
- 238000001514 detection method Methods 0.000 claims abstract description 20
- 239000012491 analyte Substances 0.000 claims abstract description 12
- 238000004458 analytical method Methods 0.000 claims abstract description 12
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 74
- 239000000460 chlorine Substances 0.000 claims description 74
- 229910052801 chlorine Inorganic materials 0.000 claims description 74
- 239000000243 solution Substances 0.000 claims description 43
- 239000000872 buffer Substances 0.000 claims description 37
- 239000000463 material Substances 0.000 claims description 29
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims description 22
- 238000000034 method Methods 0.000 claims description 22
- IOLCXVTUBQKXJR-UHFFFAOYSA-M potassium bromide Chemical compound [K+].[Br-] IOLCXVTUBQKXJR-UHFFFAOYSA-M 0.000 claims description 22
- 235000010413 sodium alginate Nutrition 0.000 claims description 22
- 239000000661 sodium alginate Substances 0.000 claims description 22
- 229940005550 sodium alginate Drugs 0.000 claims description 22
- 239000011575 calcium Substances 0.000 claims description 17
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 16
- 229910052791 calcium Inorganic materials 0.000 claims description 15
- 239000008363 phosphate buffer Substances 0.000 claims description 14
- IWZKICVEHNUQTL-UHFFFAOYSA-M potassium hydrogen phthalate Chemical compound [K+].OC(=O)C1=CC=CC=C1C([O-])=O IWZKICVEHNUQTL-UHFFFAOYSA-M 0.000 claims description 13
- 229920000867 polyelectrolyte Polymers 0.000 claims description 11
- HFVAFDPGUJEFBQ-UHFFFAOYSA-M alizarin red S Chemical compound [Na+].O=C1C2=CC=CC=C2C(=O)C2=C1C=C(S([O-])(=O)=O)C(O)=C2O HFVAFDPGUJEFBQ-UHFFFAOYSA-M 0.000 claims description 10
- 239000002202 Polyethylene glycol Substances 0.000 claims description 9
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 claims description 9
- 229920001223 polyethylene glycol Polymers 0.000 claims description 9
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 9
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 9
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 8
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 8
- 229910052709 silver Inorganic materials 0.000 claims description 8
- 239000004332 silver Substances 0.000 claims description 8
- AYLDJQABCMPYEN-UHFFFAOYSA-N (4-azaniumylphenyl)-diethylazanium;sulfate Chemical compound OS(O)(=O)=O.CCN(CC)C1=CC=C(N)C=C1 AYLDJQABCMPYEN-UHFFFAOYSA-N 0.000 claims description 7
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 7
- 239000002824 redox indicator Substances 0.000 claims description 7
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 7
- 235000019422 polyvinyl alcohol Nutrition 0.000 claims description 6
- QVRFMRZEAVHYMX-UHFFFAOYSA-L manganese(2+);diperchlorate Chemical compound [Mn+2].[O-]Cl(=O)(=O)=O.[O-]Cl(=O)(=O)=O QVRFMRZEAVHYMX-UHFFFAOYSA-L 0.000 claims description 5
- 239000008351 acetate buffer Substances 0.000 claims description 3
- KZMRYBLIGYQPPP-UHFFFAOYSA-N 3-[[[4-[(2-chlorophenyl)-[4-[ethyl-[(3-sulfonatophenyl)methyl]azaniumylidene]cyclohexa-2,5-dien-1-ylidene]methyl]phenyl]-ethylazaniumyl]methyl]benzenesulfonate Chemical compound C=1C=C(C(=C2C=CC(C=C2)=[N+](CC)CC=2C=C(C=CC=2)S([O-])(=O)=O)C=2C(=CC=CC=2)Cl)C=CC=1[NH+](CC)CC1=CC=CC(S([O-])(=O)=O)=C1 KZMRYBLIGYQPPP-UHFFFAOYSA-N 0.000 claims description 2
- GLUKPDKNLKRLHX-UHFFFAOYSA-N 4-n,4-n-dimethylbenzene-1,4-diamine;sulfuric acid Chemical compound OS(O)(=O)=O.CN(C)C1=CC=C(N)C=C1 GLUKPDKNLKRLHX-UHFFFAOYSA-N 0.000 claims description 2
- ATJXMQHAMYVHRX-CPCISQLKSA-N Ellagic acid Natural products OC1=C(O)[C@H]2OC(=O)c3cc(O)c(O)c4OC(=O)C(=C1)[C@H]2c34 ATJXMQHAMYVHRX-CPCISQLKSA-N 0.000 claims description 2
- KWYHDKDOAIKMQN-UHFFFAOYSA-N N,N,N',N'-tetramethylethylenediamine Chemical compound CN(C)CCN(C)C KWYHDKDOAIKMQN-UHFFFAOYSA-N 0.000 claims description 2
- RGCKGOZRHPZPFP-UHFFFAOYSA-N alizarin Chemical compound C1=CC=C2C(=O)C3=C(O)C(O)=CC=C3C(=O)C2=C1 RGCKGOZRHPZPFP-UHFFFAOYSA-N 0.000 claims description 2
- SXYCCJAPZKHOLS-UHFFFAOYSA-N chembl2008674 Chemical compound [O-][N+](=O)C1=CC=C2C(N=NC3=C4C=CC=CC4=CC=C3O)=C(O)C=C(S(O)(=O)=O)C2=C1 SXYCCJAPZKHOLS-UHFFFAOYSA-N 0.000 claims description 2
- SNWKSPIFHCTHRU-UHFFFAOYSA-L disodium;3-[[4-hydroxy-9,10-dioxo-2-(4-sulfonatoanilino)anthracen-1-yl]amino]benzenesulfonate Chemical compound [Na+].[Na+].C=1C=CC(S([O-])(=O)=O)=CC=1NC=1C=2C(=O)C3=CC=CC=C3C(=O)C=2C(O)=CC=1NC1=CC=C(S([O-])(=O)=O)C=C1 SNWKSPIFHCTHRU-UHFFFAOYSA-L 0.000 claims description 2
- 150000004989 p-phenylenediamines Chemical class 0.000 claims description 2
- ZHFPEICFUVWJIS-UHFFFAOYSA-M sodium 2-hydroxy-5-[(3-nitrophenyl)diazenyl]benzoate Chemical compound [Na+].Oc1ccc(cc1C([O-])=O)N=Nc1cccc(c1)[N+]([O-])=O ZHFPEICFUVWJIS-UHFFFAOYSA-M 0.000 claims description 2
- 229910001507 metal halide Inorganic materials 0.000 claims 3
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 150000005309 metal halides Chemical class 0.000 claims 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 18
- 239000000976 ink Substances 0.000 description 12
- 229920000642 polymer Polymers 0.000 description 11
- 238000000151 deposition Methods 0.000 description 10
- 230000008021 deposition Effects 0.000 description 10
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 10
- 239000007853 buffer solution Substances 0.000 description 9
- 238000002360 preparation method Methods 0.000 description 8
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 7
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 7
- QNGVNLMMEQUVQK-UHFFFAOYSA-N 4-n,4-n-diethylbenzene-1,4-diamine Chemical compound CCN(CC)C1=CC=C(N)C=C1 QNGVNLMMEQUVQK-UHFFFAOYSA-N 0.000 description 6
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Chemical compound BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 6
- 229910001424 calcium ion Inorganic materials 0.000 description 6
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- -1 hydrogen ions Chemical class 0.000 description 6
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 4
- QDHHCQZDFGDHMP-UHFFFAOYSA-N Chloramine Chemical class ClN QDHHCQZDFGDHMP-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 238000000835 electrochemical detection Methods 0.000 description 4
- 229920003023 plastic Polymers 0.000 description 4
- 239000004033 plastic Substances 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 3
- 238000003149 assay kit Methods 0.000 description 3
- 230000003139 buffering effect Effects 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- XAEFZNCEHLXOMS-UHFFFAOYSA-M potassium benzoate Chemical compound [K+].[O-]C(=O)C1=CC=CC=C1 XAEFZNCEHLXOMS-UHFFFAOYSA-M 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- WAEMQWOKJMHJLA-UHFFFAOYSA-N Manganese(2+) Chemical class [Mn+2] WAEMQWOKJMHJLA-UHFFFAOYSA-N 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Inorganic materials Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 150000002697 manganese compounds Chemical class 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
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- 150000002739 metals Chemical class 0.000 description 2
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- 229910052697 platinum Inorganic materials 0.000 description 2
- 229920000728 polyester Polymers 0.000 description 2
- 239000004800 polyvinyl chloride Substances 0.000 description 2
- 229920000915 polyvinyl chloride Polymers 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011253 protective coating Substances 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 2
- 241000894006 Bacteria Species 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- ZKQDCIXGCQPQNV-UHFFFAOYSA-N Calcium hypochlorite Chemical compound [Ca+2].Cl[O-].Cl[O-] ZKQDCIXGCQPQNV-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 241000195493 Cryptophyta Species 0.000 description 1
- 241000233866 Fungi Species 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- 229910021380 Manganese Chloride Inorganic materials 0.000 description 1
- GLFNIEUTAYBVOC-UHFFFAOYSA-L Manganese chloride Chemical compound Cl[Mn]Cl GLFNIEUTAYBVOC-UHFFFAOYSA-L 0.000 description 1
- 229910019093 NaOCl Inorganic materials 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000005708 Sodium hypochlorite Substances 0.000 description 1
- 241000700605 Viruses Species 0.000 description 1
- 239000002696 acid base indicator Substances 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 238000004082 amperometric method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910001914 chlorine tetroxide Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002405 diagnostic procedure Methods 0.000 description 1
- JSYGRUBHOCKMGQ-UHFFFAOYSA-N dichloramine Chemical compound ClNCl JSYGRUBHOCKMGQ-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
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- 239000007788 liquid Substances 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 229940071125 manganese acetate Drugs 0.000 description 1
- 239000011565 manganese chloride Substances 0.000 description 1
- 235000002867 manganese chloride Nutrition 0.000 description 1
- 229940099607 manganese chloride Drugs 0.000 description 1
- 229940099596 manganese sulfate Drugs 0.000 description 1
- 239000011702 manganese sulphate Substances 0.000 description 1
- 235000007079 manganese sulphate Nutrition 0.000 description 1
- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 description 1
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 1
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000012811 non-conductive material Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000000123 paper Substances 0.000 description 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Chemical compound [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000011012 sanitization Methods 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
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- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000003826 tablet Substances 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/27—Association of two or more measuring systems or cells, each measuring a different parameter, where the measurement results may be either used independently, the systems or cells being physically associated, or combined to produce a value for a further parameter
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/307—Disposable laminated or multilayered electrodes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
- G01N27/4045—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors for gases other than oxygen
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/4166—Systems measuring a particular property of an electrolyte
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
- G01N33/182—Specific anions in water
Definitions
- the present invention relates to an electrochemical sensor for detection and analysis of one or more analytes in water.
- Chlorine disinfects or sanitizes water by destroying harmful microorganisms, such as bacteria, fungi, and viruses and also controls nuisance organisms, including algae that may be occur in recreational water, filtration device, and piping.
- Available chlorine is the major component of chlorine species, which is mainly composed of a class of chemicals that produce hypochlorous acid (HOCl), when is dissolved in water.
- hypochlorous acid HOCl
- chlorine either as gaseous chorine, sodium hypochlorite, or calcium hypochlorite dissolves in water it produces HOCl, and at the pH range of 5-6 chlorine exists as HOCl:
- hypochlorous acid may then dissociate into hydrogen ions (H + ) and hypochlorite ions (OCl ⁇ ) and the hypochlorite ions (OCl ⁇ ) become more predominant at higher pH of 7.2-7.5.
- Chlorine in the forms of Cl 2 , HOCl, or OCl ⁇ is known as free available chlorine, and these three forms of chlorine may present in water and their relative amounts in water depends on pH and to a slight extent on temperature.
- Total available chlorine is the sum of free available chlorine and combined available chlorine.
- the relative amount of combined available chlorine also depends on pH and temperature, and the concentration of inorganic or organic amines in water.
- the combined chlorine undergoes limited hydrolysis in water and has less oxidizing power than free available chlorine. It is therefore important to distinguish free available chlorine and combined available chlorine to measure the disinfection strength of residual chlorine.
- Total hardness is the measure of water hardness.
- Calcium and Magnesium ions are the primary sources of water hardness. In general, calcium represents about 97% of the water hardness in pool water and the level of dissolved calcium is kept ideally between 200 to 500 ppm. Pool water requires the appropriate level of water hardness. High calcium hardness can result in cloudy water and scale formation due to the precipitation of calcium carbonate from the water, whereas low calcium can lead to corrosion.
- Total alkalinity is the measure of the pool water's buffering capacity to resist pH change.
- the buffering capacity of alkalinity in water is due to carbonate, bicarbonate, hydroxide, and sometimes borates, silicates and phosphate, but is mainly measured by the amount of carbonate and bicarbonate in pool water. Further, at a desirable pH range of 7.2-7.6 in pool water most of the carbonate ions are in the bicarbonate ions from which buffering is provided.
- total alkalinity is kept between 60-150 ppm depending on the sanitizing system being used and without a proper control of total alkalinity pH of the water rises or falls abruptly, causing the water to form scale and becomes cloudy or corrosive. The level of total alkalinity is tested and adjusted before adjusting pH.
- Test kits that are currently available for the analysis of water hardness and total alkalinity are based on the use of specific dye reagents or acid-base indicators, followed by the spectrometric analysis or titration where changes in color in test solution are monitored.
- specific dye reagents or acid-base indicators followed by the spectrometric analysis or titration where changes in color in test solution are monitored.
- interferences and human error in monitoring the color change for testing for hardness or alkalinity in water, leading to erroneous test results.
- diagnostic test kits or devices to accurately and easily measure the contents of free chlorine, total chlorine, total hardness, and total alkalinity in recreational water. The present invention provides an answer to that need.
- the present invention provides an electrochemical sensor for detection and analysis of an analyte in a solution.
- the electrochemical sensor has an electrically non-conductive support; a plurality of electrodes on the support, each electrode having a first surface and an opposite second surface, said first surface facing towards the support and the second surface facing away from the support.
- the plurality of electrodes includes a reference electrode, a counter electrode, and a working electrode.
- the working electrode has a reagent composition containing a reagent for detecting an analyte applied directly to the second surface of the working electrode.
- the electrochemical sensor of the present invention may have working electrodes for the detection and analysis of water for free chlorine, total chlorine, total alkalinity and/or hardness of the water.
- the present invention is directed to method of analyzing water.
- the method includes placing the electrochemical sensor in a display device and placing the electrodes of the sensor in water to be analyzed.
- FIG. 1 shows a top plan view of the electrochemical sensor having a single working electrode.
- FIG. 2 shows an exaggerated cross-sectional side view of the electrochemical sensor along section line 2 - 2 viewing the working electrode.
- FIG. 3 shows an exaggerated cross-sectional side view of the electrochemical sensor along section line 3 - 3 viewing the counter electrode.
- FIG. 4 shows an exaggerated cross-sectional front view of the electrochemical sensor along section line 4 - 4 viewing the electrodes.
- FIG. 5 shows and top plan view of the electrochemical sensor having a plurality of electrodes.
- the electrochemical sensor 10 has a support 12 which has a plurality of electrodes 14 , disposed on support 12 .
- the electrodes 14 may be disposed on both sides of the support or only on one side of the support.
- the electrodes 14 are spaced about a suitable distance so that the electrodes 14 are independent from each other.
- Electrodes 14 include a reference electrode 16 , a counter electrode 18 and a working electrode 20 . Operation of each of these electrodes will be described in more detail below.
- each electrode 14 has a first surface 21 adjacent support 12 and a second surface 22 , which is opposite the first surface 21 and the second surface 22 faces away from the support 12 .
- the support 12 also has plurality of connectors 30 disposed thereon, which serve to connect the electrochemical sensor to an instrument, which will allow a user of the electrochemical sensor 10 to take readings from the sensor.
- the connectors 30 are generally on the same surface of the support 12 as electrodes 14 , but are generally positioned away from the end of the support containing electrodes 14 . It is possible for the connectors 30 to be on the opposite end of the support from the electrodes 14 , as is shown in FIG. 1 , or, in the alternative, connectors 30 may be located along the sides of the support 12 .
- the electrodes 14 are each separately electrically connected to separate connectors 30 .
- Each electrode 14 may be directly connected to a connector 30 , or may be connected via a conductive track 40 which is disposed on the support 12 .
- Each conductive track 40 serves to connect a given connector 30 to a given electrode 14 , without crossing another conductive track 40 .
- a protective coating 50 is optionally applied over the support 12 , in all or most of the area in which the conductive tracks 40 are present.
- Support 12 is prepared from a material which is electrically non-conductive and inert to the testing environment and chemicals applied thereto to form the electrodes 14 , the connectors 30 and the conductive tracks 40 .
- Suitable materials useable for the support include, for example, ceramic, paper, plastic or glass materials.
- the support 12 is generally flexible to a degree so that the support 12 , electrodes 14 , connectors 30 and conductive tracks 40 are not damaged due to handling prior to use.
- support 12 is prepared from a dielectric plastic material.
- Exemplary plastic materials usable for the support include polyester, polycarbonate and polyvinylchloride. Other polymeric plastic materials may also be used without departing from the scope and spirit of the present invention.
- the support should have a cost associated therewith which allows the sensor to be disposable after use.
- the electrodes 14 may be disposed on the support using any of a variety of techniques known to those skilled in the art. Suitable techniques include, for example, screen printing, lithography, vapor deposition, spray coating, vacuum deposition, inkjet printing or other similar techniques. Each electrode 14 is prepared from a conductive composition which is applied to the support 12 . Suitable conductive compositions include conductive inks with may be screen printed or inkjet printed onto the support 12 . Conductive inks include inks that contain conductive particles in the ink. Exemplary conductive particles include metal particles of conductive metals, such as gold, silver, platinum and conductive noble metal, carbon particles or other similar conductive polymers.
- the materials that may be used for the counter electrode 18 and the working electrode 20 include carbon, metal or metal-carbon mixture.
- a silver based ink or a silver/silver chloride based ink may be used for the reference electrode 14 .
- silver/silver chloride based inks are used for the reference electrode 14 .
- the connectors 30 may be prepared from any conductive material including copper, gold, silver, platinum or other similar conductive metals. Generally, the connectors 30 will be prepared from the same ink material used to prepare one or more of the electrodes, from an ease of manufacture standpoint. In one embodiment of the present invention, the connectors 30 are each prepared from the same material used to prepare the reference electrode 14 . For example, the connectors may be prepared form a silver/silver chloride based ink.
- the connecting tracks 40 when present, are also prepared from a conductive ink and is applied using the same techniques mentioned above for the disposition of the electrodes to the substrate. Generally, the connecting tracks 40 will be prepared from the same ink material used to prepare the connectors 30 or electrodes 14 . By using the same material, the sensor can be quickly and easily manufactured. In one embodiment, the connecting tracks are prepared from a silver/silver chloride based ink.
- connecting tracks 40 may be provided with a protective insulation coating 50 .
- Protective insulation coating 50 can be prepared from any electrically non-conductive material that will effective adhere to the support 12 and the conductive tracks 40 .
- Exemplary materials include, for example, dielectric polymeric materials such as polyesters, polyvinyl chloride and other similar compatible polymers. It is noted that the protective coating does not need to cover the entirety of the connecting tracks 40 , but will need to cover the connecting tracks where the connecting tracks 40 connect to the electrodes 14 . This will prevent the connecting tracks 40 from coming into contact with the water to be tested, as the electrodes 14 are placed in the water to be tested.
- reference electrode 16 and counter electrode 18 are prepared from different materials.
- working electrode 20 is prepared from the same material as the counter electrode 18 ; however, working electrode 20 has a reagent composition 26 applied to the second surface 22 of the working electrode 20 , as is shown in FIG. 2 , which show a cross-section of the electrochemical sensor 10 , along section line 2 - 2 in FIG. 1 .
- the reagent composition 26 applied to the working electrode 20 determines the analyte that the working electrode 22 will detect and analyze. Comparing the cross-section of the electrochemical sensor along the working electrode 20 shown of FIG. 2 to the cross-section of electrochemical sensor along the counter electrode 18 shown in FIG.
- FIG. 4 shows the front-side view of the electrochemical sensor 10 of the present invention. Again, it can be seen that the working electrode 20 has a reagent composition 26 applied to the second surface 22 of the working electrode 20 . It can also be seen that the reference electrode 16 , the counter electrode 18 and the working electrode 20 are spaced apart on the support 12 . This allows each of these electrodes to be electrically insulated from one another.
- the reagent composition applied to the working electrode is modified with appropriate reagents for the individual detection of free chlorine, total chlorine, calcium hardness, or total alkalinity.
- Each working electrode will have a reagent composition applied to the second surface of that working electrode.
- the sensor 10 may have multiple working electrodes, as shown in FIG. 5 . As can be seen in FIG. 5 , there are multiple working electrodes 201 , 202 , 203 . Each working 201 , 202 and 203 , may have a different reagent composition applied to the surface. Alternatively, when multiple working electrodes are present, two or more working electrodes may have the same reagent. When multiple working electrodes are present, the only limitation to the number of electrodes is the space available the surface of the support 12 . It is contemplated that electrodes could be on both sides of the support. Generally, there will be between about 2 and about 8 working electrodes on the sensor.
- Detection of each analyte is based on the amperometric analysis using a specific reagent or reagent mixtures deposited on the working electrode.
- the amperometric method is a controlled-potential electrochemical technique, where the current response to an applied potential is measured by a potentiostat.
- a potentiostat is an electronic instrument that controls the voltage difference between a working electrode and a reference electrode. Any type of commercially available or custom-made portable, field-deployable potentiostat may be used. In the case of labs, non-portable potentiostats may be used. An exemplary commercially available potentiostat is a Uniscan Instruments, Ltd.
- Model PG581 Potentiostat having office in Buxton, United Kingdoms. It is also contemplated that other potentiostats, or other items such as smart phones with applications (software) could also function as a potentiostats for the electrochemical sensors of the present invention.
- the sensor is polarized at a potential value (vs. Ag/AgCl) for a time period. The current observed at a given time is recorded and averaged using the software embedded in the potentiostat. The concentration of analyte is then determined using the average current value and the pre-loaded calibration table in the instrument.
- the free chlorine reagent composition for the free chorine electrochemical sensor measures the content of free chlorine in water by the amperometric analysis.
- the reagent composition for the free chlorine electrochemical sensor will generally contain a redox indicator reagent, a buffer and a polymeric material.
- water is used as the solvent for the composition and the components are added so that the resulting composition has the component present in an amount disclosed below.
- These components are generally mixed and applied to the second surface of the working electrode. The solvent is removed by drying the composition at an elevated temperature for a period of time.
- Suitable redox indicator reagents include, for example p-phenylenediamine salts, N,N-diethyl-p-phenylenediamine sulfate salt (DPD), N,N-dimethyl-p-phenylenediamine sulfate salt, and N,N,N′N′-tetramethyl-p-phenylenediamine.
- the redox indicator reagent component is added to the reagent composition to form a solution which is about 0.01 M to about 0.20 M, and more typically in a 0.03 to about a 0.07 M.
- Suitable buffers include phthalate buffers, phosphate buffers.
- Phosphate buffers include, for example disodium hydrogen phosphate, sodium di-hydrogen phosphate, and mixtures thereof.
- the buffer component is generally present in the reagent composition in the range of about 0.01 to about 0.03 M.
- Sodium chloride is generally added to the buffer in a concentration of about 0.3 to about 0.6 M. Typically, it is added in an amount of about 0.4 to about 0.5 M.
- the reagent composition will also have a polymeric component added to assist disposition of the redox indicator reagent to the surface of the electrode.
- the polymeric material in the reagent composition is used to retain reagent and buffer mixture on the electrode surface, and stabilizing the response of electrochemical detection.
- Possible polymers include, for example, polyethylene glycol, sodium alginate, polyvinyl alcohol, or other similar polyelectrolyte polymers. Generally, polyethylene glycol is used for the free chlorine sensor. Typically, the polymer is added in an amount of about 0.1 to about 2.0% by weight, based on the volume of the solution.
- the amount of free chlorine is measured by generating a voltage applied from the reference electrode and the resulting current from the working electrode is measured, according to the reaction shown below:
- the sensor is polarized at a potential value (vs Ag/AgCl) for a time period.
- the current observed at 15-30 seconds is averaged using the software embeded in the potentiostat.
- the concentration of free chlorine is then determined using the average current value and the pre-loaded calibration table in the instrument.
- the total chlorine reagent composition for the total chorine electrochemical sensor measures the content of total chlorine in water by the amperometric analysis.
- the reagent composition for the total chlorine electrochemical sensor will generally contain a potassium halide salt, a buffer component and a polymeric material.
- deionized water is used as the solvent for the composition and the components are added so that the resulting composition has the component present in an amount disclosed below.
- These components are generally mixed and applied to the second surface of the working electrode to form the total chlorine working electrode.
- the potassium halide salt added to the reagent composition may be potassium bromide, and potassium chloride.
- the potassium salt is added in an amount such that the potassium salt is present in a concentration of about of 0.05 to 2M typically about 0.25 to about 0.75 M.
- concentration of potassium bromide is a concentration of potassium bromide.
- Suitable buffers include phthalate buffers, phosphate buffers.
- Phosphate buffers include, for example disodium hydrogen phosphate, sodium di-hydrogen phosphate and mixtures thereof.
- Suitable phthalate buffers include potassium hydrogen phthalate.
- the buffer component is generally present in the reagent composition in the range of about 0.01 to about 0.3 M.
- the pH of the buffer solution should be adjusted to the range around 3-4 pH is generally adjusted using a diluted hydrochloric acid (HCl), such as 0.1 M HCl.
- the reagent composition will also have a polymeric component added to assist disposition of the potassium salt and buffer to the surface of the electrode.
- the polymeric material in the reagent composition is used to retain reagent and buffer mixture on the electrode surface, and stabilizing the response of electrochemical detection.
- Possible polymers include, for example, polyvinyl alcohol, sodium alginate, or other similar polyelectrolyte polymers. Generally, sodium alginate is used is used for the total chlorine sensor. Typically, the polymer is added in an amount of about 0.1 to about 2.0% by weight, based on the weight of the solution.
- Total chlorine is measured amperometically by applying a voltage to the electrode and measuring the current from the working electrode. Combined chlorine is then determined by difference between the total chlorine and free chlorine contents. Potassium bromide can react with free chlorine and combined chlorine as follows:
- the liberated bromine is reduced electrochemically at the electrode as shown below:
- the calcium hardness sensor according to the invention measures the content of calcium ion in water by the amperometric analysis.
- the reagent used in the calcium hardness reagent composition is an electrochemical indicator for the detection of calcium ion and other complexometric indicators.
- the reagent composition for the hardness electrochemical sensor will generally contain an electrochemical indicator for the detection of calcium ion and other complexometric indicators, a buffer component and a polymeric material.
- deionized water is used as the solvent for the composition and the components are added so that the resulting composition has the component present in an amount disclosed below.
- the electrochemical indicator for the detection of calcium ion and other complexometric indicators are generally present in the reagent composition in an amount in the range of about 1 to 10 mM, typically about 2-4 mM.
- Suitable compounds for this component include Alizarin Red, Alizarin Yellow CG, Alizarin Green, Alizarin Blue Black B, and Eriochrome Black T.
- Alizarin Red S (3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt) is typically used as an electrochemical indicator for the detection of calcium ion.
- Suitable buffers include phthalate buffers, phosphate buffers and an acetate buffer.
- Phosphate buffers include, for example disodium hydrogen phosphate, sodium di-hydrogen phosphate and mixtures thereof.
- Suitable phthalate buffers include potassium hydrogen phthalate.
- the buffer component is generally present in the reagent composition in the range of about 0.01 to about 0.3 M.
- the pH of the buffer solution should be adjusted to the range around 3-4 pH is generally adjusted using a diluted hydrochloric acid (HCl), such as 0.1 M HCl.
- the reagent composition will also have a polymeric component added to assist disposition of the Alizarin Red S and buffer to the surface of the electrode.
- the polymeric material in the reagent composition is used to retain reagent and buffer mixture on the electrode surface, and stabilizing the response of electrochemical detection.
- Possible polymers include, for example, polyvinyl alcohol, polyvinylpyrrolidone, sodium alginate, or other similar polyelectrolyte polymers. Generally, sodium alginate is used is used for the calcium hardness sensor. Typically, the polymer is added in an amount of about 0.05 to about 1.0% by weight, based on the weight of the solution.
- Suitable buffers include phthalate buffer, phosphate buffer, and acetate buffer in a pH range of 3.0 to 4.0.
- Suitable polymer materials may include, but not limited to sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone or other polyelectrolytes.
- the total alkalinity sensor according to the invention measures the contents of carbonate and bicarbonate in water by the amperometric analysis using manganese compound as the reagent.
- Suitable manganese compounds include, for example, manganese (II) salts, including but not limited to manganese perchlorate, manganese acetate, manganese chloride, manganese nitrate, manganese sulfate.
- the reagent composition uses manganese (II) perchlorate as the reagent and a polymeric material.
- the manganese (II) perchlorate reagent is generally present in a concentration of 5 to 100 mM, typically between about 20 to 40 mM.
- the reagent composition will also have a polymeric component added to assist disposition of the manganese (II) perchlorate to the surface of the electrode.
- the polymeric material in the reagent composition is used to retain reagent on the electrode surface, and stabilize the response of electrochemical detection.
- Possible polymers include, for example, polyvinyl alcohol, polyvinylpyrrolidone, sodium alginate, or other similar polyelectrolyte polymers. Generally, polyvinylpyrrolidone is used for the total alkalinity sensor.
- the polymer is added in an amount of about 0.5 to about 5.0% by weight, based on the volume of the solution.
- the polymeric component will be about 1.5 to about 3% by weight of the composition.
- the Mn-bicarbonate complex is then oxidized electrochemically at the electrode as shown below:
- the polymeric electrolyte's in each of the reagent compositions functions to reduce the current passed by the working electrode and stabilize the signals to achieve sensitivity and consistency through creating plurality of working electrodes, via the creation of individual crystalline regions resulted from drying of reagents on top of the working electrode.
- Crystals formed in the polymer matrix by drying in the oven for specific amount of time and temperature.
- the polymer will act as a holding matrix for the crystals to be entrapped creating apertures of crystals on the surface of the electrode. Therefore, each crystal will act as a working electrode via a controlled dissolution of crystals and polymeric surface. The number and sizes of these apertures may be controlled by reagent concentration and drying time and temperature.
- an optional hood or cover may be placed over the electrodes to help protect the electrodes prior to use and to assist in holding the sample of water to be tested near the electrodes.
- the shape of electrochemical sensors is generally rectangular in shape, as shown in FIGS. 1-5 , but any other conventional shapes such as square or circular type shapes may also be used without departing from the scope of the present invention.
- a pH 7 buffer solution was prepared by dissolving 0.013 M of disodium hydrogen phosphate, 0.007 M sodium di-hydrogen phosphate, and 0.45 M sodium chloride in deionized water. Then 1.33 wt. % polyethylene glycol (PEG) was added and dissolved in the solution. The solution was allowed to rest for 5 minutes and then 0.05 M N,N-diethyl-p-phenylenediamine sulfate salt (DPD) was added to the solution. The resulting mixture was shaken vigorously to dissolve the DPD into the solution.
- PEG polyethylene glycol
- DPD N,N-diethyl-p-phenylenediamine sulfate salt
- a portion of the solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode.
- the total amount of the solution deposited on the working electrode was about 7.14 ⁇ L.
- a 0.1 M of potassium hydrogen phthalate pH 3.5 buffer solution was prepared in deionized water. To this solution was added 18% (v:v) of 0.1 M HCl. Then 0.03 g of sodium alginate per 15 mL of the buffer solution was dissolved in the solution. The solution was allowed to rest for 5 minutes at room temperature. Next, 0.5 M potassium bromide was added to the solution and the solution was vigorously shaken to dissolve the potassium bromide in the buffer solution.
- the final deposition solution concentrations of the solution was: potassium hydrogen phthalate about 0.1 M, hydrochloric acid about 0.0176 M, potassium bromide about 0.5 M and sodium alginate about 0.2% (w:v).
- a portion of the total chlorine detection reagent solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode.
- the total amount of the solution deposited on the working electrode was about 7.14 ⁇ L.
- a 0.1 M of potassium hydrogen phthalate buffer solution (pH 3.4) was prepared in deionized water. To this solution was added was 18% (v:v) of 0.1 M HCl. Then 0.03 g of sodium alginate per 15 mL of the buffer solutions was dissolved into the solution. Then 0.03 g of sodium alginate was dissolved in the solution per 15 mL of the solution. The solution is allowed to rest for 5 minutes at room temperature. Next 0.003 M Alizarin Red S (3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt) was added to the solution and to the solution was vigorously shaken to dissolve the Alizarin Red S into the buffer solution.
- Alizarin Red S 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt
- the final deposition solution concentrations of the solution was: potassium hydrogen phthalate about 0.1 M, hydrochloric acid about 0.0176 M, Alizarin Red S about 3 mM, and sodium alginate about 0.2% (w:v).
- a portion of the calcium hardness reagent solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode.
- the total amount of the solution deposited on the working electrode was about 7.14 ⁇ L.
- the total alkalinity reagent composition was prepared by dissolving 2% by weight of polyvinylpyrrolidone (0.3 g/15 mL) in deionized water to prepare a solution. To this solution, 40 mM (152 mg/15 mL) of Mn(ClO 4 ) 2 .6 H 2 O was added. The mixture was shaken until the components were dissolved. The resulting solution was the total alkalinity reagent solution.
- a portion of the total alkalinity reagent solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode.
- the total amount of the solution deposited on the working electrode was about 7.14 ⁇ L.
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Abstract
Description
- This application is a divisional of U.S. patent application Ser. No. 14/032,891, filed Sep. 20, 2013, which claims priority under 35 U.S.C. § 119(e) from Provisional Application No. 61/704,139 filed Sep. 21, 2012, the disclosures of which are incorporated herein by reference.
- The present invention relates to an electrochemical sensor for detection and analysis of one or more analytes in water.
- Chemicals have been added to pools and other water supplies to disinfect and sanitize the water so that the quality of the water is useable for its intended purpose. There are a number of factors that affect water quality, including water chemistry parameters. The major chemistry parameters that are associated with maintaining water quality includes free available chlorine, total available chlorine, total hardness, total alkalinity, as well as pH. It is therefore important to monitor and control these chemistry parameters for water quality management, especially for water such as recreational and industrial water.
- Chlorine disinfects or sanitizes water by destroying harmful microorganisms, such as bacteria, fungi, and viruses and also controls nuisance organisms, including algae that may be occur in recreational water, filtration device, and piping. Available chlorine is the major component of chlorine species, which is mainly composed of a class of chemicals that produce hypochlorous acid (HOCl), when is dissolved in water. When chlorine, either as gaseous chorine, sodium hypochlorite, or calcium hypochlorite dissolves in water it produces HOCl, and at the pH range of 5-6 chlorine exists as HOCl:
-
Cl2+H2O═HOCl+H++Cl− -
NaOCl+H2O═HOCl+Na++OH− -
Ca(OCl)2+2H2O═Ca(OH)2+2HOCl - The hypochlorous acid may then dissociate into hydrogen ions (H+) and hypochlorite ions (OCl−) and the hypochlorite ions (OCl−) become more predominant at higher pH of 7.2-7.5.
-
HOCl═H++OCl− - Chlorine in the forms of Cl2, HOCl, or OCl− is known as free available chlorine, and these three forms of chlorine may present in water and their relative amounts in water depends on pH and to a slight extent on temperature.
- Combined available chlorine refers to any chlorine species associated with inorganic chloramines (NH2Cl and NHCl2) and organic chloramines (RNHCl, R=alkyl) in water. Total available chlorine is the sum of free available chlorine and combined available chlorine. The relative amount of combined available chlorine also depends on pH and temperature, and the concentration of inorganic or organic amines in water. However, the combined chlorine undergoes limited hydrolysis in water and has less oxidizing power than free available chlorine. It is therefore important to distinguish free available chlorine and combined available chlorine to measure the disinfection strength of residual chlorine.
- Total hardness is the measure of water hardness. Calcium and Magnesium ions are the primary sources of water hardness. In general, calcium represents about 97% of the water hardness in pool water and the level of dissolved calcium is kept ideally between 200 to 500 ppm. Pool water requires the appropriate level of water hardness. High calcium hardness can result in cloudy water and scale formation due to the precipitation of calcium carbonate from the water, whereas low calcium can lead to corrosion.
- Total alkalinity is the measure of the pool water's buffering capacity to resist pH change. The buffering capacity of alkalinity in water is due to carbonate, bicarbonate, hydroxide, and sometimes borates, silicates and phosphate, but is mainly measured by the amount of carbonate and bicarbonate in pool water. Further, at a desirable pH range of 7.2-7.6 in pool water most of the carbonate ions are in the bicarbonate ions from which buffering is provided. In general, total alkalinity is kept between 60-150 ppm depending on the sanitizing system being used and without a proper control of total alkalinity pH of the water rises or falls abruptly, causing the water to form scale and becomes cloudy or corrosive. The level of total alkalinity is tested and adjusted before adjusting pH.
- There is a continuous interest in developing simple, rapid, and reliable methods for the determination of water chemistry parameters, including but not limited to free chlorine, combined chlorine, hardness, and total alkalinity. For example, because chlorine species in water are very reactive and may dissipate very quickly the reliable and accurate measurements of residual chlorine in water are difficult. There are a number of field test kits available for the determination of free and combined available chlorine in water, which is mostly based on the use of DPD (diethyl p-phenylenediamine). DPD test kits are manufactured with either liquid, powder or tablet reagents. Test kits that are currently available for the analysis of water hardness and total alkalinity are based on the use of specific dye reagents or acid-base indicators, followed by the spectrometric analysis or titration where changes in color in test solution are monitored. However, there are often interferences and human error in monitoring the color change for testing for hardness or alkalinity in water, leading to erroneous test results. At present, there are no simple, rapid, cost effective and reliable diagnostic test kits or devices to accurately and easily measure the contents of free chlorine, total chlorine, total hardness, and total alkalinity in recreational water. The present invention provides an answer to that need.
- In one aspect, the present invention provides an electrochemical sensor for detection and analysis of an analyte in a solution. The electrochemical sensor has an electrically non-conductive support; a plurality of electrodes on the support, each electrode having a first surface and an opposite second surface, said first surface facing towards the support and the second surface facing away from the support. The plurality of electrodes includes a reference electrode, a counter electrode, and a working electrode. The working electrode has a reagent composition containing a reagent for detecting an analyte applied directly to the second surface of the working electrode.
- The electrochemical sensor of the present invention may have working electrodes for the detection and analysis of water for free chlorine, total chlorine, total alkalinity and/or hardness of the water.
- In another embodiment of the present invention is directed to method of analyzing water. The method includes placing the electrochemical sensor in a display device and placing the electrodes of the sensor in water to be analyzed.
- These and other aspects will become apparent when reading the detailed description of the invention.
-
FIG. 1 shows a top plan view of the electrochemical sensor having a single working electrode. -
FIG. 2 shows an exaggerated cross-sectional side view of the electrochemical sensor along section line 2-2 viewing the working electrode. -
FIG. 3 shows an exaggerated cross-sectional side view of the electrochemical sensor along section line 3-3 viewing the counter electrode. -
FIG. 4 shows an exaggerated cross-sectional front view of the electrochemical sensor along section line 4-4 viewing the electrodes. -
FIG. 5 shows and top plan view of the electrochemical sensor having a plurality of electrodes. - To gain a better understanding of the present invention, attention is directed to the drawings. The drawings are not intended to be limiting but are intended for understating the present invention. It has now been surprisingly found the electrochemical sensor of the present invention is able to perform without the need of (i.e., omits) an intermediate layer between the electrode and the reagent composition. It has been found that the sensor of the present invention has simplicity of manufacture and has sensitivity to give a sensor with reproducible results.
- Turning to
FIG. 1 , shown is a top view of theelectrochemical sensor 10. Theelectrochemical sensor 10 has asupport 12 which has a plurality ofelectrodes 14, disposed onsupport 12. Theelectrodes 14 may be disposed on both sides of the support or only on one side of the support. Theelectrodes 14 are spaced about a suitable distance so that theelectrodes 14 are independent from each other.Electrodes 14 include areference electrode 16, acounter electrode 18 and a workingelectrode 20. Operation of each of these electrodes will be described in more detail below. As can be seen inFIGS. 2 and 3 , eachelectrode 14 has afirst surface 21adjacent support 12 and asecond surface 22, which is opposite thefirst surface 21 and thesecond surface 22 faces away from thesupport 12. - The
support 12 also has plurality ofconnectors 30 disposed thereon, which serve to connect the electrochemical sensor to an instrument, which will allow a user of theelectrochemical sensor 10 to take readings from the sensor. Theconnectors 30 are generally on the same surface of thesupport 12 aselectrodes 14, but are generally positioned away from the end of thesupport containing electrodes 14. It is possible for theconnectors 30 to be on the opposite end of the support from theelectrodes 14, as is shown inFIG. 1 , or, in the alternative,connectors 30 may be located along the sides of thesupport 12. - The
electrodes 14 are each separately electrically connected to separateconnectors 30. Eachelectrode 14 may be directly connected to aconnector 30, or may be connected via aconductive track 40 which is disposed on thesupport 12. Eachconductive track 40 serves to connect a givenconnector 30 to a givenelectrode 14, without crossing anotherconductive track 40. To protect theconductive tracks 40, aprotective coating 50 is optionally applied over thesupport 12, in all or most of the area in which theconductive tracks 40 are present. -
Support 12 is prepared from a material which is electrically non-conductive and inert to the testing environment and chemicals applied thereto to form theelectrodes 14, theconnectors 30 and the conductive tracks 40. Suitable materials useable for the support include, for example, ceramic, paper, plastic or glass materials. Generally, from a standpoint of cost and durability, thesupport 12 is generally flexible to a degree so that thesupport 12,electrodes 14,connectors 30 andconductive tracks 40 are not damaged due to handling prior to use. Generally,support 12 is prepared from a dielectric plastic material. Exemplary plastic materials usable for the support include polyester, polycarbonate and polyvinylchloride. Other polymeric plastic materials may also be used without departing from the scope and spirit of the present invention. Ideally, the support should have a cost associated therewith which allows the sensor to be disposable after use. - The
electrodes 14 may be disposed on the support using any of a variety of techniques known to those skilled in the art. Suitable techniques include, for example, screen printing, lithography, vapor deposition, spray coating, vacuum deposition, inkjet printing or other similar techniques. Eachelectrode 14 is prepared from a conductive composition which is applied to thesupport 12. Suitable conductive compositions include conductive inks with may be screen printed or inkjet printed onto thesupport 12. Conductive inks include inks that contain conductive particles in the ink. Exemplary conductive particles include metal particles of conductive metals, such as gold, silver, platinum and conductive noble metal, carbon particles or other similar conductive polymers. In one embodiment of the present invention, the materials that may be used for thecounter electrode 18 and the workingelectrode 20 include carbon, metal or metal-carbon mixture. A silver based ink or a silver/silver chloride based ink may be used for thereference electrode 14. Generally, silver/silver chloride based inks are used for thereference electrode 14. - The
connectors 30 may be prepared from any conductive material including copper, gold, silver, platinum or other similar conductive metals. Generally, theconnectors 30 will be prepared from the same ink material used to prepare one or more of the electrodes, from an ease of manufacture standpoint. In one embodiment of the present invention, theconnectors 30 are each prepared from the same material used to prepare thereference electrode 14. For example, the connectors may be prepared form a silver/silver chloride based ink. - The connecting tracks 40, when present, are also prepared from a conductive ink and is applied using the same techniques mentioned above for the disposition of the electrodes to the substrate. Generally, the connecting
tracks 40 will be prepared from the same ink material used to prepare theconnectors 30 orelectrodes 14. By using the same material, the sensor can be quickly and easily manufactured. In one embodiment, the connecting tracks are prepared from a silver/silver chloride based ink. - To protect the connecting
tracks 40 from damage prior or during use, and to prevent the connectingtracks 40 from acting like a reference electrode, if they come into contact with the water to be tested, connectingtracks 40 may be provided with aprotective insulation coating 50.Protective insulation coating 50 can be prepared from any electrically non-conductive material that will effective adhere to thesupport 12 and the conductive tracks 40. Exemplary materials include, for example, dielectric polymeric materials such as polyesters, polyvinyl chloride and other similar compatible polymers. It is noted that the protective coating does not need to cover the entirety of the connectingtracks 40, but will need to cover the connecting tracks where the connectingtracks 40 connect to theelectrodes 14. This will prevent the connectingtracks 40 from coming into contact with the water to be tested, as theelectrodes 14 are placed in the water to be tested. - In the present invention,
reference electrode 16 andcounter electrode 18 are prepared from different materials. Generally, workingelectrode 20 is prepared from the same material as thecounter electrode 18; however, workingelectrode 20 has areagent composition 26 applied to thesecond surface 22 of the workingelectrode 20, as is shown inFIG. 2 , which show a cross-section of theelectrochemical sensor 10, along section line 2-2 inFIG. 1 . Thereagent composition 26 applied to the workingelectrode 20 determines the analyte that the workingelectrode 22 will detect and analyze. Comparing the cross-section of the electrochemical sensor along the workingelectrode 20 shown ofFIG. 2 to the cross-section of electrochemical sensor along thecounter electrode 18 shown inFIG. 3 , it can be seen that thecounter electrode 18 does not have areagent composition 26 applied thereto, while workingelectrode 20 does.FIG. 4 shows the front-side view of theelectrochemical sensor 10 of the present invention. Again, it can be seen that the workingelectrode 20 has areagent composition 26 applied to thesecond surface 22 of the workingelectrode 20. It can also be seen that thereference electrode 16, thecounter electrode 18 and the workingelectrode 20 are spaced apart on thesupport 12. This allows each of these electrodes to be electrically insulated from one another. - The reagent composition applied to the working electrode is modified with appropriate reagents for the individual detection of free chlorine, total chlorine, calcium hardness, or total alkalinity. Each working electrode will have a reagent composition applied to the second surface of that working electrode. The
sensor 10 may have multiple working electrodes, as shown inFIG. 5 . As can be seen inFIG. 5 , there are multiple workingelectrodes support 12. It is contemplated that electrodes could be on both sides of the support. Generally, there will be between about 2 and about 8 working electrodes on the sensor. - Detection of each analyte is based on the amperometric analysis using a specific reagent or reagent mixtures deposited on the working electrode. The amperometric method is a controlled-potential electrochemical technique, where the current response to an applied potential is measured by a potentiostat. A potentiostat is an electronic instrument that controls the voltage difference between a working electrode and a reference electrode. Any type of commercially available or custom-made portable, field-deployable potentiostat may be used. In the case of labs, non-portable potentiostats may be used. An exemplary commercially available potentiostat is a Uniscan Instruments, Ltd. Model PG581 Potentiostat, having office in Buxton, United Kingdoms. It is also contemplated that other potentiostats, or other items such as smart phones with applications (software) could also function as a potentiostats for the electrochemical sensors of the present invention. In general, the sensor is polarized at a potential value (vs. Ag/AgCl) for a time period. The current observed at a given time is recorded and averaged using the software embedded in the potentiostat. The concentration of analyte is then determined using the average current value and the pre-loaded calibration table in the instrument.
- The reagent compositions useable in the present invention will now be described.
- Free Chlorine Detection Reagent Composition
- The free chlorine reagent composition for the free chorine electrochemical sensor according to the invention, measures the content of free chlorine in water by the amperometric analysis. The reagent composition for the free chlorine electrochemical sensor will generally contain a redox indicator reagent, a buffer and a polymeric material. Typically, water is used as the solvent for the composition and the components are added so that the resulting composition has the component present in an amount disclosed below. These components are generally mixed and applied to the second surface of the working electrode. The solvent is removed by drying the composition at an elevated temperature for a period of time.
- Suitable redox indicator reagents include, for example p-phenylenediamine salts, N,N-diethyl-p-phenylenediamine sulfate salt (DPD), N,N-dimethyl-p-phenylenediamine sulfate salt, and N,N,N′N′-tetramethyl-p-phenylenediamine. The redox indicator reagent component is added to the reagent composition to form a solution which is about 0.01 M to about 0.20 M, and more typically in a 0.03 to about a 0.07 M.
- Suitable buffers include phthalate buffers, phosphate buffers. Phosphate buffers include, for example disodium hydrogen phosphate, sodium di-hydrogen phosphate, and mixtures thereof. The buffer component is generally present in the reagent composition in the range of about 0.01 to about 0.03 M.
- Sodium chloride is generally added to the buffer in a concentration of about 0.3 to about 0.6 M. Typically, it is added in an amount of about 0.4 to about 0.5 M.
- In addition, the reagent composition will also have a polymeric component added to assist disposition of the redox indicator reagent to the surface of the electrode. In addition, the polymeric material in the reagent composition is used to retain reagent and buffer mixture on the electrode surface, and stabilizing the response of electrochemical detection. Possible polymers include, for example, polyethylene glycol, sodium alginate, polyvinyl alcohol, or other similar polyelectrolyte polymers. Generally, polyethylene glycol is used for the free chlorine sensor. Typically, the polymer is added in an amount of about 0.1 to about 2.0% by weight, based on the volume of the solution.
- In the electrochemical sensor containing a free chlorine reagent composition applied to the working electrode, the amount of free chlorine is measured by generating a voltage applied from the reference electrode and the resulting current from the working electrode is measured, according to the reaction shown below:
-
HOCl+2e−↔Cl−+OH− - The sensor is polarized at a potential value (vs Ag/AgCl) for a time period. The current observed at 15-30 seconds is averaged using the software embeded in the potentiostat. The concentration of free chlorine is then determined using the average current value and the pre-loaded calibration table in the instrument.
- Total Chlorine Detection Reagent Composition
- The total chlorine reagent composition for the total chorine electrochemical sensor according to the invention, measures the content of total chlorine in water by the amperometric analysis. The reagent composition for the total chlorine electrochemical sensor will generally contain a potassium halide salt, a buffer component and a polymeric material. Typically, deionized water is used as the solvent for the composition and the components are added so that the resulting composition has the component present in an amount disclosed below. These components are generally mixed and applied to the second surface of the working electrode to form the total chlorine working electrode.
- The potassium halide salt added to the reagent composition may be potassium bromide, and potassium chloride. Generally, the potassium salt is added in an amount such that the potassium salt is present in a concentration of about of 0.05 to 2M typically about 0.25 to about 0.75 M. One specific example is a 0.5M concentration of potassium bromide.
- Suitable buffers include phthalate buffers, phosphate buffers. Phosphate buffers include, for example disodium hydrogen phosphate, sodium di-hydrogen phosphate and mixtures thereof. Suitable phthalate buffers include potassium hydrogen phthalate. The buffer component is generally present in the reagent composition in the range of about 0.01 to about 0.3 M. The pH of the buffer solution should be adjusted to the range around 3-4 pH is generally adjusted using a diluted hydrochloric acid (HCl), such as 0.1 M HCl.
- In addition, the reagent composition will also have a polymeric component added to assist disposition of the potassium salt and buffer to the surface of the electrode. In addition, the polymeric material in the reagent composition is used to retain reagent and buffer mixture on the electrode surface, and stabilizing the response of electrochemical detection. Possible polymers include, for example, polyvinyl alcohol, sodium alginate, or other similar polyelectrolyte polymers. Generally, sodium alginate is used is used for the total chlorine sensor. Typically, the polymer is added in an amount of about 0.1 to about 2.0% by weight, based on the weight of the solution.
- Total chlorine is measured amperometically by applying a voltage to the electrode and measuring the current from the working electrode. Combined chlorine is then determined by difference between the total chlorine and free chlorine contents. Potassium bromide can react with free chlorine and combined chlorine as follows:
-
OCl−+2Br−+2H+↔Br2+Cl−+H2O -
Cl2+2Br−↔Br2+2Cl− -
NH2Cl+2Br−+2H+↔Br2+Cl−+NH4 + -
RNHCl+2Br−+2H+↔Br2+Cl−+RNH3 + - The liberated bromine is reduced electrochemically at the electrode as shown below:
-
Br2+2e −↔2Br− - Calcium Hardness Detection Reagent Composition
- The calcium hardness sensor according to the invention measures the content of calcium ion in water by the amperometric analysis. The reagent used in the calcium hardness reagent composition is an electrochemical indicator for the detection of calcium ion and other complexometric indicators. The reagent composition for the hardness electrochemical sensor will generally contain an electrochemical indicator for the detection of calcium ion and other complexometric indicators, a buffer component and a polymeric material. Typically, deionized water is used as the solvent for the composition and the components are added so that the resulting composition has the component present in an amount disclosed below.
- The electrochemical indicator for the detection of calcium ion and other complexometric indicators are generally present in the reagent composition in an amount in the range of about 1 to 10 mM, typically about 2-4 mM. Suitable compounds for this component include Alizarin Red, Alizarin Yellow CG, Alizarin Green, Alizarin Blue Black B, and Eriochrome Black T. Of these, Alizarin Red S (3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt) is typically used as an electrochemical indicator for the detection of calcium ion.
- Suitable buffers include phthalate buffers, phosphate buffers and an acetate buffer. Phosphate buffers include, for example disodium hydrogen phosphate, sodium di-hydrogen phosphate and mixtures thereof. Suitable phthalate buffers include potassium hydrogen phthalate. The buffer component is generally present in the reagent composition in the range of about 0.01 to about 0.3 M. The pH of the buffer solution should be adjusted to the range around 3-4 pH is generally adjusted using a diluted hydrochloric acid (HCl), such as 0.1 M HCl.
- In addition, the reagent composition will also have a polymeric component added to assist disposition of the Alizarin Red S and buffer to the surface of the electrode. In addition, the polymeric material in the reagent composition is used to retain reagent and buffer mixture on the electrode surface, and stabilizing the response of electrochemical detection. Possible polymers include, for example, polyvinyl alcohol, polyvinylpyrrolidone, sodium alginate, or other similar polyelectrolyte polymers. Generally, sodium alginate is used is used for the calcium hardness sensor. Typically, the polymer is added in an amount of about 0.05 to about 1.0% by weight, based on the weight of the solution.
- Suitable buffers include phthalate buffer, phosphate buffer, and acetate buffer in a pH range of 3.0 to 4.0. Suitable polymer materials may include, but not limited to sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone or other polyelectrolytes.
- Total Alkalinity Detection Reagent Composition
- The total alkalinity sensor according to the invention measures the contents of carbonate and bicarbonate in water by the amperometric analysis using manganese compound as the reagent. Suitable manganese compounds include, for example, manganese (II) salts, including but not limited to manganese perchlorate, manganese acetate, manganese chloride, manganese nitrate, manganese sulfate. Typically, the reagent composition uses manganese (II) perchlorate as the reagent and a polymeric material. The manganese (II) perchlorate reagent is generally present in a concentration of 5 to 100 mM, typically between about 20 to 40 mM.
- In addition, the reagent composition will also have a polymeric component added to assist disposition of the manganese (II) perchlorate to the surface of the electrode. In addition, the polymeric material in the reagent composition is used to retain reagent on the electrode surface, and stabilize the response of electrochemical detection. Possible polymers include, for example, polyvinyl alcohol, polyvinylpyrrolidone, sodium alginate, or other similar polyelectrolyte polymers. Generally, polyvinylpyrrolidone is used for the total alkalinity sensor. Generally, the polymer is added in an amount of about 0.5 to about 5.0% by weight, based on the volume of the solution. Typically the polymeric component will be about 1.5 to about 3% by weight of the composition.
- Mn2+ ions complex with bicarbonate ions at a desirable pH range of 7.2-7.6 in pool water as shown below:
-
Mn2+(aq)+2HCO3 −↔[Mn(HCO3)2] - The Mn-bicarbonate complex is then oxidized electrochemically at the electrode as shown below:
-
[Mn(HCO3)2]↔Mn3++2HCO3 − +e − - Although not wishing to be bound by theory, it is believed that the polymeric electrolyte's in each of the reagent compositions functions to reduce the current passed by the working electrode and stabilize the signals to achieve sensitivity and consistency through creating plurality of working electrodes, via the creation of individual crystalline regions resulted from drying of reagents on top of the working electrode. Crystals formed in the polymer matrix by drying in the oven for specific amount of time and temperature. The polymer will act as a holding matrix for the crystals to be entrapped creating apertures of crystals on the surface of the electrode. Therefore, each crystal will act as a working electrode via a controlled dissolution of crystals and polymeric surface. The number and sizes of these apertures may be controlled by reagent concentration and drying time and temperature.
- Other features may be present on the electrochemical sensor of the present invention. For example, an optional hood or cover may be placed over the electrodes to help protect the electrodes prior to use and to assist in holding the sample of water to be tested near the electrodes.
- The shape of electrochemical sensors is generally rectangular in shape, as shown in
FIGS. 1-5 , but any other conventional shapes such as square or circular type shapes may also be used without departing from the scope of the present invention. - A. Preparation of Free Chlorine Sensor
- Preparation of Free Chlorine Detection Reagent Solution
- A pH 7 buffer solution was prepared by dissolving 0.013 M of disodium hydrogen phosphate, 0.007 M sodium di-hydrogen phosphate, and 0.45 M sodium chloride in deionized water. Then 1.33 wt. % polyethylene glycol (PEG) was added and dissolved in the solution. The solution was allowed to rest for 5 minutes and then 0.05 M N,N-diethyl-p-phenylenediamine sulfate salt (DPD) was added to the solution. The resulting mixture was shaken vigorously to dissolve the DPD into the solution.
- Deposition Procedure
- A portion of the solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode. The total amount of the solution deposited on the working electrode was about 7.14 μL. Once deposition procedure was completed, the electrochemical senor was carefully placed in an oven at 100° C. for 15 minutes. The sensor was removed from the oven and allowed to cool for a period of time of at least 5 minutes.
- B. Preparation of Total Chlorine Sensor
- Preparation of Total Chlorine Detection Reagent Solution
- A 0.1 M of potassium hydrogen phthalate pH 3.5 buffer solution was prepared in deionized water. To this solution was added 18% (v:v) of 0.1 M HCl. Then 0.03 g of sodium alginate per 15 mL of the buffer solution was dissolved in the solution. The solution was allowed to rest for 5 minutes at room temperature. Next, 0.5 M potassium bromide was added to the solution and the solution was vigorously shaken to dissolve the potassium bromide in the buffer solution.
- The final deposition solution concentrations of the solution was: potassium hydrogen phthalate about 0.1 M, hydrochloric acid about 0.0176 M, potassium bromide about 0.5 M and sodium alginate about 0.2% (w:v).
- Deposition Procedure
- A portion of the total chlorine detection reagent solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode. The total amount of the solution deposited on the working electrode was about 7.14 μL. Once deposition procedure was completed, the electrochemical senor was carefully placed in an oven at 100° C. for 15 minutes. The sensor was removed from the oven and allowed to cool for a period of time of at least 5 minutes.
- C. Preparation of Calcium Hardness Sensor
- Preparation of Calcium Hardness Detection Reagent Solution
- A 0.1 M of potassium hydrogen phthalate buffer solution (pH 3.4) was prepared in deionized water. To this solution was added was 18% (v:v) of 0.1 M HCl. Then 0.03 g of sodium alginate per 15 mL of the buffer solutions was dissolved into the solution. Then 0.03 g of sodium alginate was dissolved in the solution per 15 mL of the solution. The solution is allowed to rest for 5 minutes at room temperature. Next 0.003 M Alizarin Red S (3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt) was added to the solution and to the solution was vigorously shaken to dissolve the Alizarin Red S into the buffer solution.
- The final deposition solution concentrations of the solution was: potassium hydrogen phthalate about 0.1 M, hydrochloric acid about 0.0176 M, Alizarin Red S about 3 mM, and sodium alginate about 0.2% (w:v).
- Deposition Procedure
- A portion of the calcium hardness reagent solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode. The total amount of the solution deposited on the working electrode was about 7.14 μL. Once the deposition procedure has been completed, the electrochemical senor was carefully placed in an oven at 50° C. for 20 mins. The sensor was removed from the oven and allowed to cool for a period of time of at least 5 minutes.
- Preparation of Total Alkalinity Sensor
- Preparation of Total Alkalinity Detection Reagent Solution
- The total alkalinity reagent composition was prepared by dissolving 2% by weight of polyvinylpyrrolidone (0.3 g/15 mL) in deionized water to prepare a solution. To this solution, 40 mM (152 mg/15 mL) of Mn(ClO4)2.6 H2O was added. The mixture was shaken until the components were dissolved. The resulting solution was the total alkalinity reagent solution.
- Deposition Procedure
- A portion of the total alkalinity reagent solution was deposited on a carbon working electrode present on an electrochemical sensor having a reference electrode and a counter electrode. The total amount of the solution deposited on the working electrode was about 7.14 μL. Once deposition procedure was completed, the electrochemical senor was carefully placed in an oven at 100° C. for 15 minutes. The sensor was removed from the oven and allowed to cool for a period of time of at least 5 minutes.
- While the invention has been described above with references to specific embodiments thereof, it is apparent that many changes, modifications and variations can be made without departing from the invention concept disclosed herein. Accordingly, it is intended to embrace all such changes, modifications, and variations that fall within the spirit and broad scope of the appended claims.
Claims (36)
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IT201700046831A1 (en) * | 2017-05-03 | 2018-11-03 | Tecnosens S R L | New nano and / or microstructured printed sensors. |
US10935508B2 (en) * | 2017-08-28 | 2021-03-02 | Xiamen Eco Lighting Co. Ltd. | Liquid detection device and liquid detection system for abnormal liquid on a surface |
CN109991294B (en) * | 2019-04-23 | 2022-02-18 | 南京腾森分析仪器有限公司 | Membrane electrode, preparation method thereof, sensor using membrane electrode, electrochemical workstation and application of electrochemical workstation |
JP2021060363A (en) * | 2019-10-09 | 2021-04-15 | 昭和電工マテリアルズ株式会社 | Water quality monitoring system |
GB2599115A (en) * | 2020-09-24 | 2022-03-30 | Palintest Ltd | Electrochemical sensor |
CN114184664B (en) * | 2021-11-12 | 2024-04-26 | 上海纳米技术及应用国家工程研究中心有限公司 | Preparation method of Ti-ZIF-67 electrochemical sensor for detecting ammonium ions, product and application thereof |
US11965847B2 (en) * | 2021-12-16 | 2024-04-23 | Nxp B.V. | Reconfigurable architecture analog front end for electrochemical sensors |
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US4176032A (en) | 1978-03-03 | 1979-11-27 | Fischer & Porter Co. | Chlorine dioxide analyzer |
ES2154280T3 (en) | 1993-11-02 | 2001-04-01 | Siemens Plc | WATER QUALITY SENSOR DEVICE. |
US20080035481A1 (en) | 2004-03-04 | 2008-02-14 | Mccormack Sean P | Electrochemical Sensors |
GB0517773D0 (en) | 2005-09-01 | 2005-10-12 | Palintest Ltd | Electrochemical sensor |
US8262874B2 (en) * | 2008-04-14 | 2012-09-11 | Abbott Diabetes Care Inc. | Biosensor coating composition and methods thereof |
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