CN103884749B - Formaldehyde electrochemical detection system and working electrode preparation method and Analysis Methods for Formaldehyde - Google Patents
Formaldehyde electrochemical detection system and working electrode preparation method and Analysis Methods for Formaldehyde Download PDFInfo
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- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 title claims abstract description 289
- 238000000835 electrochemical detection Methods 0.000 title claims abstract description 25
- 238000002360 preparation method Methods 0.000 title claims description 5
- 238000004458 analytical method Methods 0.000 title description 4
- 230000003750 conditioning effect Effects 0.000 claims abstract description 20
- 238000004891 communication Methods 0.000 claims abstract description 12
- 239000002048 multi walled nanotube Substances 0.000 claims description 82
- 229910052799 carbon Inorganic materials 0.000 claims description 53
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 50
- 238000000034 method Methods 0.000 claims description 40
- 239000011259 mixed solution Substances 0.000 claims description 35
- 102000004190 Enzymes Human genes 0.000 claims description 27
- 108090000790 Enzymes Proteins 0.000 claims description 27
- 239000000243 solution Substances 0.000 claims description 27
- 238000010790 dilution Methods 0.000 claims description 24
- 239000012895 dilution Substances 0.000 claims description 24
- 239000012188 paraffin wax Substances 0.000 claims description 21
- 239000006229 carbon black Substances 0.000 claims description 18
- 239000000843 powder Substances 0.000 claims description 15
- 239000012086 standard solution Substances 0.000 claims description 13
- 238000001514 detection method Methods 0.000 claims description 12
- 238000001914 filtration Methods 0.000 claims description 12
- 239000000155 melt Substances 0.000 claims description 12
- BOPGDPNILDQYTO-NNYOXOHSSA-N nicotinamide-adenine dinucleotide Chemical compound C1=CCC(C(=O)N)=CN1[C@H]1[C@H](O)[C@H](O)[C@@H](COP(O)(=O)OP(O)(=O)OC[C@@H]2[C@H]([C@@H](O)[C@@H](O2)N2C3=NC=NC(N)=C3N=C2)O)O1 BOPGDPNILDQYTO-NNYOXOHSSA-N 0.000 claims description 10
- 239000008363 phosphate buffer Substances 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 239000011521 glass Substances 0.000 claims description 9
- 239000012456 homogeneous solution Substances 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 9
- 238000007254 oxidation reaction Methods 0.000 claims description 8
- 102100039702 Alcohol dehydrogenase class-3 Human genes 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
- 108010051015 glutathione-independent formaldehyde dehydrogenase Proteins 0.000 claims description 6
- 239000011812 mixed powder Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000005498 polishing Methods 0.000 claims description 4
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims description 3
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 3
- 239000004411 aluminium Substances 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 150000001721 carbon Chemical class 0.000 claims description 3
- 230000015556 catabolic process Effects 0.000 claims description 3
- 238000006555 catalytic reaction Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 239000003431 cross linking reagent Substances 0.000 claims description 3
- 238000006731 degradation reaction Methods 0.000 claims description 3
- 239000012154 double-distilled water Substances 0.000 claims description 3
- 238000005868 electrolysis reaction Methods 0.000 claims description 3
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 238000005259 measurement Methods 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 3
- 230000008018 melting Effects 0.000 claims description 3
- 239000004570 mortar (masonry) Substances 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- 230000008054 signal transmission Effects 0.000 claims description 3
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 3
- 230000036962 time dependent Effects 0.000 claims description 3
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 abstract description 4
- 230000003647 oxidation Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 3
- 239000003014 ion exchange membrane Substances 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229930040373 Paraformaldehyde Natural products 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000010411 cooking Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000037213 diet Effects 0.000 description 1
- 235000005911 diet Nutrition 0.000 description 1
- 230000002255 enzymatic effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000011900 installation process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 229920002866 paraformaldehyde Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
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- Apparatus Associated With Microorganisms And Enzymes (AREA)
Abstract
The invention discloses formaldehyde electrochemical detection system, one end of its first interface channel and the first reservoir, one end of second interface channel is communicated with second container, the other end of the first interface channel is communicated with by amberplex with between the other end of the second interface channel, working electrode and contrast electrode are positioned at the first container, second container is positioned to electrode, the electric current positive pole Survey control port of the communication port connection signal modulate circuit of working electrode, to the electric current negative pole Survey control port of the communication port connection signal modulate circuit of electrode, the potential state of the communication port connection signal modulate circuit of contrast electrode stablizes port, the signal input part of the signal output part connection signal processor of signal conditioning circuit.The present invention utilizes linear relationship good between Faradaic current signal and the concentration of formaldehyde, makes the present invention can detect the content of formaldehyde in food faster, even if the formaldehyde only in food with trace also can detect.
Description
Technical field
The present invention relates to formaldehyde examination technical field, refer to a kind of formaldehyde electrochemical detection system and working electrode preparation method and Analysis Methods for Formaldehyde particularly.
Background technology
Along with economic society constantly progress, economic globalization development, the variation of people's cooking culture, but the security performance of food directly has influence on the healthy of the people, therefore the safety problem of food becomes the hot issue of World Focusing gradually, but food-safety problem is mainly derived from the safety detection of food, so the safety detection of food is also a global problem.Therefore national governments all take strong measure to ensure the safety of food, and domestic and international market is more and more stricter to the quality requirements of food, also more and more higher to the requirement of food safety detection technology.But present stage the detection method that applies in actual testing process all more loaded down with trivial details and expensive, be difficult to be detected fast and effectively, therefore current new requirement proposed to food safety detection technology.If various food can be made to obtain safety detection fast and effectively, the safe diet of the people can be ensured, also can improve the competitiveness in market.
Sensor for detecting formaldehyde has optical sensor and photoproduction sensor.Optical sensor price comparison is expensive, and volume is comparatively large, and be not suitable on line real time, the popularity making it use is restricted.Although light biochemical sensor improves selectivity, because the activity of enzyme and other factors cause sensor unstable, lack practicality, and the selling at exorbitant prices of general formaldehyde gas sensor, be difficult to popularize.
Summary of the invention
Object of the present invention will provide a kind of formaldehyde electrochemical detection system and working electrode preparation method and Analysis Methods for Formaldehyde exactly, the present invention utilizes linear relationship good between Faradaic current signal and the concentration of formaldehyde, the formaldehyde only in food with trace make the present invention can detect the content of formaldehyde in food faster, even if also can utilize the solution of the present invention to detect.
Formaldehyde electrochemical detection system designed by the present invention, it comprises working electrode, contrast electrode, to electrode, first container, second container, signal conditioning circuit, signal processor, first interface channel, second interface channel, wherein, one end of described first interface channel and the first reservoir, one end of second interface channel is communicated with second container, the other end of described first interface channel is communicated with by amberplex with between the other end of the second interface channel, described working electrode and contrast electrode are positioned at the first container, described second container is positioned to electrode, the electric current positive pole Survey control port of the communication port connection signal modulate circuit of described working electrode, the electric current negative pole Survey control port of the described communication port connection signal modulate circuit to electrode, the potential state of the communication port connection signal modulate circuit of described contrast electrode stablizes port, the signal input part of the signal output part connection signal processor of above-mentioned signal conditioning circuit, described working electrode is the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly, contrast electrode is silver chloride reference electrode, be platinum electrode to electrode.
Preferably, it also comprises the amberplex mounting cylinder between the other end and the other end of the second interface channel being arranged on the first interface channel, amberplex is installed in the inner side of amberplex mounting cylinder, the other end of described first interface channel is provided with the first flange, the other end of the second interface channel is provided with the second flange, described first interface channel, amberplex mounting cylinder is fixedly connected with the second flange by the first flange with the second interface channel, one end of described amberplex mounting cylinder offers first annular groove coaxial with amberplex mounting cylinder, the other end of the first interface channel is provided with the first annular flange flange that is coaxial with the first interface channel and that mate with the first annular groove, the other end of above-mentioned amberplex mounting cylinder offers second annular groove coaxial with amberplex mounting cylinder, the other end of the second interface channel is provided with the second annular flange flange that is coaxial with the second interface channel and that mate with the second annular groove, O-ring seal is provided with between described first annular groove and the first annular flange flange, also O-ring seal is provided with between described second annular groove and the second annular flange flange.
Preferably, it also comprises amberplex installing ring, and the inner ring of described amberplex installing ring is fixedly connected with amberplex, is interference fit between the outer ring of amberplex installing ring and the inner ring of amberplex mounting cylinder.
Prepare a method for working electrode in formaldehyde electrochemical detection system, it comprises the steps:
Step 1: be heated to 80 DEG C by water-bath in the salpeter solution of 20 ~ 35% at mass percent concentration by the multi-walled carbon nano-tubes of 1 ~ 50 gram, and the multi-walled carbon nano-tubes of 80 DEG C is stirred 48 hours in above-mentioned salpeter solution, then centrifugal treating is carried out to the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed, magazins' layout on multi-walled carbon nano-tubes is got off, the salpeter solution containing above-mentioned multi-walled carbon nano-tubes impurity is removed after centrifugal treating terminates, take out multi-walled carbon nano-tubes, with water, multi-walled carbon nano-tubes is washed till neutrality, then multi-walled carbon nano-tubes is dried, obtain the multi-walled carbon nano-tubes of purifying,
Step 2: the mass ratio that carbon black and solid paraffin press 3 to 1 is ground evenly in mortar, the mixed-powder of carbon black and solid paraffin is heated, make the solid paraffin powder melts in mixed-powder, carbon black powders is embedded in the paraffin of melting, the melt paraffin this being embedded with carbon black powders loads in glass capillary, and aluminium wire is inserted in the melt paraffin being embedded with carbon black powders, the melt paraffin being embedded with carbon black powders solidifies rear formation carbon paste electrode, and is taken out from glass capillary by this carbon paste electrode;
Step 3: the multi-walled carbon nano-tubes ultrasonic disperse getting purifying in the upper step 1 of 1 ~ 20mg obtains the multi-walled carbon nano-tubes solution that concentration range is 0.1 ~ 5g/L in 1 ~ 20mL bis-double distilled water, getting 10 ~ 100 μ L concentration ranges with micro syringe is that to join 10 ~ 100 μ L mass percent concentration scopes be carry out ultrasonic disperse process in the protonated ethanolic solution of 0.01 ~ 1% for the multi-walled carbon nano-tubes solution of 0.1 ~ 5g/L, form homogeneous solution, this homogeneous solution getting 1 ~ 20 μ L is coated to described carbon paste electrode surface, placing 5 ~ 10min makes above-mentioned homogeneous solution volatilize, and form film, carbon paste electrode skin drying is made the carbon paste electrode that PEM and multi-walled carbon nano-tubes are modified jointly,
Step 4: it is in the phosphate buffer of 0.01 ~ 0.5mol/L that the shitosan of the formaldehyde dehydrogenase and 0.1 ~ 10mg that take 1 ~ 3mg is dissolved in 100 ~ 300 μ L volumetric molar concentrations, in above-mentioned phosphate buffer, add 5 ~ 30 μ L mass percents be the glutaraldehyde cross-linking agent of 1 ~ 10% and mix, form mixed liquor, the above-mentioned mixed liquor of 5 ~ 30 μ L is applied on carbon paste electrode that the PEM obtained in step 3 and multi-walled carbon nano-tubes modify jointly, be coated in the carbon paste electrode surface natural drying film forming that the mixed liquor on carbon paste electrode that PEM and multi-walled carbon nano-tubes modify jointly is modified jointly at PEM and multi-walled carbon nano-tubes, namely the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly is formed.
Preferably, in described step 1, when carrying out centrifugal treating to the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed, the rotating speed of hydro-extractor is 3500 ~ 4500r/min.
Preferably, in described step 1, bake out temperature when drying multi-walled carbon nano-tubes is 100 DEG C.
Preferably, in described step 2, after described carbon paste electrode takes out from glass capillary, carry out polishing.
Utilize above-mentioned formaldehyde electrochemical detection system to carry out a method for concentration of formaldehyde detection, it is characterized in that, it comprises the steps:
Step 100: by through confirming that the food containing formaldehyde is milled, then degradation treatment, finally therefrom extract the food extract containing formaldehyde of 1 ~ 20mL;
Step 200: get 1 ~ 10mL mass percent concentration scope be the formaldehyde standard solution of 37 ~ 40% in volumetric flask, the volumetric molar concentration scope then adding 0.1 ~ 10mL in this volumetric flask is 0.1 × 10
-3~ 10 × 10
-3the phosphate buffer of mol/L and the food extract containing formaldehyde of 1 ~ 20mL, and the mixed solution in volumetric flask is shaken up, this mixed solution is placed after 14 ~ 16 minutes and is diluted with water to 20 ~ 50mL;
Step 300: in the first container mixed solution after above-mentioned dilution being poured into above-mentioned formaldehyde electrochemical detection system and second container, mixed solution after dilution in first container and second container is by the first interface channel, amberplex is communicated with the second interface channel, stir process is carried out to the mixed solution after the dilution in the first container, in this stir process process, under the catalysis of the formaldehyde dehydrogenase composition in the carbon paste electrode that the formaldehyde in mixed solution is modified jointly at enzyme and PEM and multi-walled carbon nano-tubes, reaction generates reduced diphosphopyridine nucleotide, reduced diphosphopyridine nucleotide generation electrocatalysis oxidation reaction simultaneously, produce electrolysis electric current between the carbon paste electrode jointly modified electrode and enzyme and PEM and multi-walled carbon nano-tubes, simultaneously, hydrogen ion enters coating-forming voltage difference between the carbon paste electrode that second container makes jointly to modify electrode and enzyme and PEM and multi-walled carbon nano-tubes by amberplex and forms loop, contrast electrode is used for the effect playing burning voltage when the carbon paste electrode jointly modified enzyme and PEM and multi-walled carbon nano-tubes carries out potential measurement, the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly carries time dependent Faradaic current signal to signal conditioning circuit, signal conditioning circuit carries out filtering to above-mentioned Faradaic current signal and amplifies process, signal conditioning circuit by after filtering with amplify process after Faradaic current Signal transmissions to signal processor, signal processor to above-mentioned after filtering with amplify process after Faradaic current signal carry out computing by following algorithm, obtain total concentration of formaldehyde C of the mixed solution in step 300 after dilution,
Wherein, C is total concentration of formaldehyde of the mixed solution after dilution, I be above-mentioned after filtering with amplify process after Faradaic current signal, a is the enlargement factor of modulate circuit to current signal, t represents carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes modify the jointly T.T. to signal conditioning circuit conveying Faradaic current signal, and v represents the volume of the mixed solution after dilution;
Signal processor carries out computing to total concentration of formaldehyde C of the mixed solution after dilution by following algorithm again, obtains the concentration of formaldehyde C in food extract
1;
Wherein, C
1for the concentration of formaldehyde in food extract, v represents the volume of the mixed solution after dilution, V
1for the volume of formaldehyde standard solution, ρ is the density of formaldehyde standard solution.
Beneficial effect of the present invention:
1, the carbon paste electrode that the enzyme in the present invention and PEM and multi-walled carbon nano-tubes are modified jointly, PARA FORMALDEHYDE PRILLS(91,95) has good catalytic oxidation effect, significantly reduce the oxidation peak current potential of formaldehyde, improve the accuracy (content of formaldehyde is directly proportional to its oxidation peak current potential, only has the current potential reducing oxidation peak just can detect the formaldehyde of more low content) that content of formaldehyde detects.
2, the present invention utilizes linear relationship good between Faradaic current signal and the concentration of formaldehyde, makes the present invention can detect the content of formaldehyde in food faster.
3, formaldehyde standard solution is first added owing to this invention takes, meet the content of formaldehyde generated needed for reduced diphosphopyridine nucleotide, and in the total concentration of formaldehyde in the end calculated, remove the content of formaldehyde standard solution, finally obtain the concentration of formaldehyde in food extract accurately, also can detect even if the concentration of formaldehyde like this in food extract is very small.The susceptibility that the present invention detects formaldehyde in food is apparently higher than existing measuring method.
4, intermediate ion exchange membrane part of the present invention have employed detachable design, facilitates the cleaning of amberplex, ensure that the accuracy of the content detection of formaldehyde in food.
5, the present invention also has the advantage that cost is low, volume is little, the real-time of testing result is good, in addition, the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly reduces the oxidation peak current potential of enzymatic product, thus decrease other products to the pollution of electrode and other disturbing effects reacted, make it have good practicality and longer serviceable life.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is the structural representation of the first interface channel other end end face in the present invention;
Fig. 3 is the structural representation of the second interface channel other end end face in the present invention;
Fig. 4 is the structural representation of intermediate ion exchange membrane mounting cylinder one end of the present invention end face;
Fig. 5 is the structural representation of intermediate ion exchange membrane mounting cylinder other end end face of the present invention.
Wherein, 1-working electrode, 2-contrast electrode, 3-to electrode, the 4-the first container, 5-second container, 6-signal conditioning circuit, 7-signal processor, the 8-the first interface channel, the 9-the second interface channel, 10-amberplex, 11-amberplex mounting cylinder, the 12-the first flange, the 13-the second flange, 14-O-ring seal, the 15-the first annular groove, the 16-the first annular flange flange, the 17-the second annular groove, the 18-the second annular flange flange, 19-amberplex installing ring.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail:
Formaldehyde electrochemical detection system as shown in Fig. 1 ~ 5, it comprises working electrode 1, contrast electrode 2, to electrode 3, first container 4, second container 5, signal conditioning circuit 6, signal processor 7, first interface channel 8, second interface channel 9, wherein, one end of described first interface channel 8 is communicated with the first container 4, one end of second interface channel 9 is communicated with second container 5, the other end of described first interface channel 8 is communicated with by amberplex 10 with between the other end of the second interface channel 9, described working electrode 1 and contrast electrode 2 are positioned at the first container 4, described second container 5 is positioned to electrode 3, the electric current positive pole Survey control port of the communication port connection signal modulate circuit 6 of described working electrode 1, the electric current negative pole Survey control port of the described communication port connection signal modulate circuit 6 to electrode 3, the potential state of the communication port connection signal modulate circuit 6 of described contrast electrode 2 stablizes port, the signal input part of the signal output part connection signal processor 7 of above-mentioned signal conditioning circuit 6, described working electrode 1 is the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly, contrast electrode 2 is silver chloride reference electrode, be platinum electrode to electrode 3.
In technique scheme, it also comprises the amberplex mounting cylinder 11 between the other end and the other end of the second interface channel 9 being arranged on the first interface channel 8, amberplex 10 is installed in the inner side of amberplex mounting cylinder 11, the other end of described first interface channel 8 is provided with the first flange 12, the other end of the second interface channel 9 is provided with the second flange 13, described first interface channel 8, amberplex mounting cylinder 11 is fixedly connected with the second flange 13 by the first flange 12 with the second interface channel 9, one end of described amberplex mounting cylinder 11 offers first annular groove 15 coaxial with amberplex mounting cylinder 11, the other end of the first interface channel 8 is provided with the first annular flange flange 16 that is coaxial with the first interface channel 8 and that mate with the first annular groove 15, the other end of above-mentioned amberplex mounting cylinder 11 offers second annular groove 17 coaxial with amberplex mounting cylinder 11, the other end of the second interface channel 9 is provided with the second annular flange flange 18 that is coaxial with the second interface channel 9 and that mate with the second annular groove 17, O-ring seal 14 is provided with between described first annular groove 15 and the first annular flange flange 16, also O-ring seal 14 is provided with between described second annular groove 17 and the second annular flange flange 18.The mounting structure of above-mentioned flange achieves the dismounting of amberplex mounting cylinder 11, facilitates the cleaning to amberplex 10, improves the accuracy of the content detection of formaldehyde in food.
In technique scheme, it also comprises amberplex installing ring 19, and the inner ring of described amberplex installing ring 19 is fixedly connected with amberplex 10, is interference fit between the outer ring of amberplex installing ring 19 and the inner ring of amberplex mounting cylinder 11.Amberplex installing ring 19 adopts special top cylinder to be headed in amberplex mounting cylinder 11 in installation process.
The setting of the flange in technique scheme, annular groove and O-ring seal 14 ensure that the sealing of detachable amberplex mounting cylinder 11.
Prepare a method for working electrode in formaldehyde electrochemical detection system, it comprises the steps:
Step 1: be heated to 80 DEG C by water-bath in the salpeter solution of 20 ~ 35% at mass percent concentration by the multi-walled carbon nano-tubes of 1 ~ 50 gram, and the multi-walled carbon nano-tubes of 80 DEG C is stirred 48 hours (being stirred by mixing plant) in above-mentioned salpeter solution, then centrifugal treating is carried out to the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed, magazins' layout on multi-walled carbon nano-tubes is got off, the salpeter solution containing above-mentioned multi-walled carbon nano-tubes impurity is removed after centrifugal treating terminates, take out multi-walled carbon nano-tubes, with water, multi-walled carbon nano-tubes is washed till neutrality, then multi-walled carbon nano-tubes is dried, obtain the multi-walled carbon nano-tubes of purifying,
Step 2: the mass ratio that carbon black and solid paraffin press 3 to 1 is ground evenly in mortar, the mixed-powder of carbon black and solid paraffin is heated, make the solid paraffin powder melts in mixed-powder, carbon black powders is embedded in the paraffin of melting, the melt paraffin this being embedded with carbon black powders loads in glass capillary, and aluminium wire is inserted in the melt paraffin being embedded with carbon black powders, the melt paraffin being embedded with carbon black powders solidifies rear formation carbon paste electrode, and is taken out from glass capillary by this carbon paste electrode;
Step 3: the multi-walled carbon nano-tubes ultrasonic disperse getting purifying in the upper step 1 of 1 ~ 20mg obtains the multi-walled carbon nano-tubes solution that concentration range is 0.1 ~ 5g/L in 1 ~ 20mL bis-double distilled water, getting 10 ~ 100 μ L concentration ranges with micro syringe is that to join 10 ~ 100 μ L mass percent concentration scopes be carry out ultrasonic disperse process in the protonated ethanolic solution of 0.01 ~ 1% for the multi-walled carbon nano-tubes solution of 0.1 ~ 5g/L, form homogeneous solution, this homogeneous solution getting 1 ~ 20 μ L is coated to described carbon paste electrode surface, placing 5 ~ 10min makes above-mentioned homogeneous solution volatilize, and form film, carbon paste electrode skin drying is made the carbon paste electrode that PEM and multi-walled carbon nano-tubes are modified jointly,
Step 4: it is in the phosphate buffer of 0.01 ~ 0.5mol/L that the shitosan (for serving as bonding agent) of the formaldehyde dehydrogenase and 0.1 ~ 10mg that take 1 ~ 3mg is dissolved in 100 ~ 300 μ L volumetric molar concentrations, in above-mentioned phosphate buffer, add 5 ~ 30 μ L mass percents be the glutaraldehyde cross-linking agent of 1 ~ 10% and mix, form mixed liquor, the above-mentioned mixed liquor of 5 ~ 30 μ L is applied on carbon paste electrode that the PEM obtained in step 3 and multi-walled carbon nano-tubes modify jointly, be coated in the carbon paste electrode surface natural drying film forming that the mixed liquor on carbon paste electrode that PEM and multi-walled carbon nano-tubes modify jointly is modified jointly at PEM and multi-walled carbon nano-tubes, namely the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly is formed.
In the step 1 of technique scheme, when carrying out centrifugal treating to the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed, the rotating speed of hydro-extractor is 3500 ~ 4500r/min.Rotating speed when selecting above-mentioned hydro-extractor to work can guarantee that the salpeter solution that multi-walled carbon nano-tubes is housed is thoroughly centrifugal, makes multi-wall carbon nano-tube be in control relatively good pre-service.
In the step 1 of technique scheme, bake out temperature when drying multi-walled carbon nano-tubes is 100 DEG C.This temperature can make the oven dry of many walls nanotube be unlikely to make it fire because temperature is too high ash of charring preferably.
In the step 2 of technique scheme, after described carbon paste electrode takes out from glass capillary, carry out polishing.Polishing improves the reappearance of electrode.
Utilize above-mentioned formaldehyde electrochemical detection system to carry out a method for concentration of formaldehyde detection, it is characterized in that, it comprises the steps:
Step 100: by through confirming that the food containing formaldehyde is milled, then degradation treatment, finally therefrom extract the food extract containing formaldehyde of 1 ~ 20mL;
Step 200: get 1 ~ 10mL mass percent concentration scope be the formaldehyde standard solution of 37 ~ 40% in volumetric flask, the volumetric molar concentration scope then adding 0.1 ~ 10mL in this volumetric flask is 0.1 × 10
-3~ 10 × 10
-3the phosphate buffer (this phosphate buffer guarantees that the pH value of solution is in suitable scope) of mol/L and the food extract containing formaldehyde of 1 ~ 20mL, and the mixed solution in volumetric flask is shaken up, this mixed solution is placed after 14 ~ 16 minutes and is diluted with water to 20 ~ 50mL;
Step 300: in the first container 4 mixed solution after above-mentioned dilution being poured into above-mentioned formaldehyde electrochemical detection system and second container 5, mixed solution after dilution in first container 4 and second container 5 is by the first interface channel 8, amberplex 10 is communicated with the second interface channel 9, stir process is carried out to the mixed solution after the dilution in the first container 4, in this stir process process, under the catalysis of the formaldehyde dehydrogenase composition in the carbon paste electrode that the formaldehyde in mixed solution is modified jointly at enzyme and PEM and multi-walled carbon nano-tubes, reaction generates reduced diphosphopyridine nucleotide, reduced diphosphopyridine nucleotide generation electrocatalysis oxidation reaction simultaneously, produce electrolysis electric current between the carbon paste electrode jointly modified electrode 3 and enzyme and PEM and multi-walled carbon nano-tubes, simultaneously, hydrogen ion enters coating-forming voltage difference between the carbon paste electrode that second container 5 makes jointly to modify electrode 3 and enzyme and PEM and multi-walled carbon nano-tubes by amberplex 10 and forms loop, the effect playing burning voltage when contrast electrode 2 is for carrying out potential measurement at the carbon paste electrode jointly modified enzyme and PEM and multi-walled carbon nano-tubes (guarantees electric charge evenly movement in mixed solution, sufficient reacting carries out), the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly carries time dependent Faradaic current signal to signal conditioning circuit 6, signal conditioning circuit 6 carries out filtering to above-mentioned Faradaic current signal and amplifies process, signal conditioning circuit 6 by after filtering with amplify process after Faradaic current Signal transmissions to signal processor 7, signal processor 7 to above-mentioned after filtering with amplify process after Faradaic current signal carry out computing by following algorithm, obtain total concentration of formaldehyde C of the mixed solution in step 300 after dilution,
Wherein, C is total concentration of formaldehyde of the mixed solution after dilution, I be above-mentioned after filtering with amplify process after Faradaic current signal, a is the enlargement factor of modulate circuit 6 pairs of current signals, t represents that carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly carries the T.T. of Faradaic current signal to signal conditioning circuit 6, and v represents the volume of the mixed solution after dilution;
Signal processor 7 carries out computing to total concentration of formaldehyde C of the mixed solution after dilution by following algorithm again, obtains the concentration of formaldehyde C in food extract
1;
Right
Wherein, C
1for the concentration of formaldehyde in food extract, v represents the volume of the mixed solution after dilution, V
1for the volume of formaldehyde standard solution, ρ is the density of formaldehyde standard solution.
In technique scheme, more formaldehyde is needed owing to producing reduced diphosphopyridine nucleotide, and the content of formaldehyde in food is generally trace, be not enough to generate reduced diphosphopyridine nucleotide, so such scheme is taked to add formaldehyde standard solution to increase the method for content of formaldehyde in volumetric flask, mixed solution is made to generate reduced diphosphopyridine nucleotide, in the formaldehyde standard solution of above-mentioned increase, the content of formaldehyde is subtracted in the last computation process of step 3, obtain the content of formaldehyde in food accurately, so just can realize the detection to trace formaldehyde concentration in food.
The content that this instructions is not described in detail belongs to the known prior art of professional and technical personnel in the field.
Claims (7)
1. a formaldehyde electrochemical detection system, it is characterized in that: described formaldehyde electrochemical detection system comprises working electrode (1), contrast electrode (2), to electrode (3), first container (4), second container (5), signal conditioning circuit (6), signal processor (7), first interface channel (8), second interface channel (9), wherein, one end of described first interface channel (8) is communicated with the first container (4), one end of second interface channel (9) is communicated with second container (5), be communicated with by amberplex (10) between the other end of described first interface channel (8) and the other end of the second interface channel (9), described working electrode (1) and contrast electrode (2) are positioned at the first container (4), described second container (5) is positioned to electrode (3), the electric current positive pole Survey control port of the communication port connection signal modulate circuit (6) of described working electrode (1), the electric current negative pole Survey control port of the described communication port connection signal modulate circuit (6) to electrode (3), the potential state of the communication port connection signal modulate circuit (6) of described contrast electrode (2) stablizes port, the signal input part of the signal output part connection signal processor (7) of above-mentioned signal conditioning circuit (6), the carbon paste electrode that described working electrode (1) is modified jointly for enzyme and PEM and multi-walled carbon nano-tubes, contrast electrode (2) is silver chloride reference electrode, be platinum electrode to electrode (3),
In described formaldehyde electrochemical detection system, the preparation method of working electrode, comprises the steps:
Step 1: be heated to 80 DEG C by water-bath in the salpeter solution of 20 ~ 35% at mass percent concentration by the multi-walled carbon nano-tubes of 1 ~ 50 gram, and the multi-walled carbon nano-tubes of 80 DEG C is stirred 48 hours in above-mentioned salpeter solution, then centrifugal treating is carried out to the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed, magazins' layout on multi-walled carbon nano-tubes is got off, the salpeter solution containing above-mentioned multi-walled carbon nano-tubes impurity is removed after centrifugal treating terminates, take out multi-walled carbon nano-tubes, with water, multi-walled carbon nano-tubes is washed till neutrality, then multi-walled carbon nano-tubes is dried, obtain the multi-walled carbon nano-tubes of purifying,
Step 2: the mass ratio that carbon black and solid paraffin press 3 to 1 is ground evenly in mortar, the mixed-powder of carbon black and solid paraffin is heated, make the solid paraffin powder melts in mixed-powder, carbon black powders is embedded in the paraffin of melting, the melt paraffin being embedded with carbon black powders is loaded in glass capillary, and aluminium wire is inserted in the melt paraffin being embedded with carbon black powders, the melt paraffin being embedded with carbon black powders solidifies rear formation carbon paste electrode, and is taken out from glass capillary by this carbon paste electrode;
Step 3: the multi-walled carbon nano-tubes ultrasonic disperse getting purifying in the upper step 1 of 1 ~ 20mg obtains the multi-walled carbon nano-tubes solution that concentration range is 0.1 ~ 5g/L in 1 ~ 20mL bis-double distilled water, getting 10 ~ 100 μ L concentration ranges with micro syringe is that to join 10 ~ 100 μ L mass percent concentration scopes be carry out ultrasonic disperse process in the protonated ethanolic solution of 0.01 ~ 1% for the multi-walled carbon nano-tubes solution of 0.1 ~ 5g/L, form homogeneous solution, this homogeneous solution getting 1 ~ 20 μ L is coated to described carbon paste electrode surface, placing 5 ~ 10min makes above-mentioned homogeneous solution volatilize, and form film, carbon paste electrode skin drying is made the carbon paste electrode that PEM and multi-walled carbon nano-tubes are modified jointly,
Step 4: it is in the phosphate buffer of 0.01 ~ 0.5mol/L that the shitosan of the formaldehyde dehydrogenase and 0.1 ~ 10mg that take 1 ~ 3mg is dissolved in 100 ~ 300 μ L volumetric molar concentrations, in above-mentioned phosphate buffer, add 5 ~ 30 μ L mass percents be the glutaraldehyde cross-linking agent of 1 ~ 10% and mix, form mixed liquor, the above-mentioned mixed liquor of 5 ~ 30 μ L is applied on carbon paste electrode that the PEM obtained in step 3 and multi-walled carbon nano-tubes modify jointly, be coated in the carbon paste electrode surface natural drying film forming that the mixed liquor on carbon paste electrode that PEM and multi-walled carbon nano-tubes modify jointly is modified jointly at PEM and multi-walled carbon nano-tubes, namely the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly is formed.
2. formaldehyde electrochemical detection system according to claim 1, it is characterized in that: described formaldehyde electrochemical detection system also comprises the amberplex mounting cylinder (11) between the other end and the other end of the second interface channel (9) being arranged on the first interface channel (8), amberplex (10) is installed in the inner side of amberplex mounting cylinder (11), the other end of described first interface channel (8) is provided with the first flange (12), the other end of the second interface channel (9) is provided with the second flange (13), described first interface channel (8), amberplex mounting cylinder (11) is fixedly connected with the second flange (13) by the first flange (12) with the second interface channel (9), one end of described amberplex mounting cylinder (11) offers first annular groove (15) coaxial with amberplex mounting cylinder (11), the other end of the first interface channel (8) is provided with the first annular flange flange (16) that is coaxial with the first interface channel (8) and that mate with the first annular groove (15), the other end of above-mentioned amberplex mounting cylinder (11) offers second annular groove (17) coaxial with amberplex mounting cylinder (11), the other end of the second interface channel (9) is provided with the second annular flange flange (18) that is coaxial with the second interface channel (9) and that mate with the second annular groove (17), O-ring seal (14) is provided with between described first annular groove (15) and the first annular flange flange (16), also O-ring seal (14) is provided with between described second annular groove (17) and the second annular flange flange (18).
3. formaldehyde electrochemical detection system according to claim 2, it is characterized in that: described formaldehyde electrochemical detection system also comprises amberplex installing ring (19), the inner ring of described amberplex installing ring (19) is fixedly connected with amberplex (10), is interference fit between the outer ring of amberplex installing ring (19) and the inner ring of amberplex mounting cylinder (11).
4. formaldehyde electrochemical detection system according to claim 1, is characterized in that: in described step 1, and when carrying out centrifugal treating to the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed, the rotating speed of hydro-extractor is 3500 ~ 4500r/min.
5. formaldehyde electrochemical detection system according to claim 1, is characterized in that: in described step 1, bake out temperature when drying multi-walled carbon nano-tubes is 100 DEG C.
6. formaldehyde electrochemical detection system according to claim 1, is characterized in that: in described step 2, carries out polishing after described carbon paste electrode takes out from glass capillary.
7. utilize formaldehyde electrochemical detection system described in claim 1 to carry out a method for concentration of formaldehyde detection, it is characterized in that, it comprises the steps:
Step 100: by through confirming that the food containing formaldehyde is milled, then degradation treatment, finally therefrom extract the food extract containing formaldehyde of 1 ~ 20mL;
Step 200: get 1 ~ 10mL mass percent concentration scope be the formaldehyde standard solution of 37 ~ 40% in volumetric flask, the volumetric molar concentration scope then adding 0.1 ~ 10mL in this volumetric flask is 0.1 × 10
-3~ 10 × 10
-3the phosphate buffer of mol/L and the food extract containing formaldehyde of 1 ~ 20mL, and the mixed solution in volumetric flask is shaken up, this mixed solution is placed after 14 ~ 16 minutes and is diluted with water to 20 ~ 50mL;
Step 300: in the first container (4) mixed solution after above-mentioned dilution being poured into above-mentioned formaldehyde electrochemical detection system and second container (5), mixed solution after dilution in first container (4) and second container (5) is by the first interface channel (8), amberplex (10) is communicated with the second interface channel (9), stir process is carried out to the mixed solution after the dilution in the first container (4), in this stir process process, under the catalysis of the formaldehyde dehydrogenase composition in the carbon paste electrode that the formaldehyde in mixed solution is modified jointly at enzyme and PEM and multi-walled carbon nano-tubes, reaction generates reduced diphosphopyridine nucleotide, reduced diphosphopyridine nucleotide generation electrocatalysis oxidation reaction simultaneously, produce electrolysis electric current between the carbon paste electrode jointly modified electrode (3) and enzyme and PEM and multi-walled carbon nano-tubes, simultaneously, hydrogen ion enters coating-forming voltage difference between the carbon paste electrode that second container (5) makes jointly to modify electrode (3) and enzyme and PEM and multi-walled carbon nano-tubes by amberplex (10) and forms loop, the effect of burning voltage is played when contrast electrode (2) is for carrying out potential measurement at the carbon paste electrode jointly modified enzyme and PEM and multi-walled carbon nano-tubes, the carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes are modified jointly carries time dependent Faradaic current signal to signal conditioning circuit (6), signal conditioning circuit (6) carries out filtering to above-mentioned Faradaic current signal and amplifies process, signal conditioning circuit (6) by after filtering with amplify process after Faradaic current Signal transmissions to signal processor (7), signal processor (7) to above-mentioned after filtering with amplify process after Faradaic current signal carry out computing by following algorithm, obtain total concentration of formaldehyde C of the mixed solution in step 300 after dilution,
Wherein, C is total concentration of formaldehyde of the mixed solution after dilution, I be above-mentioned after filtering with amplify process after Faradaic current signal, a is that modulate circuit (6) is to the enlargement factor of current signal, t represents carbon paste electrode that enzyme and PEM and multi-walled carbon nano-tubes modify the jointly T.T. to signal conditioning circuit (6) conveying Faradaic current signal, and v represents the volume of the mixed solution after dilution;
Signal processor (7) carries out computing to total concentration of formaldehyde C of the mixed solution after dilution by following algorithm again, obtains the concentration of formaldehyde C in food extract
1;
Wherein, C
1for the concentration of formaldehyde in food extract, v represents the volume of the mixed solution after dilution, V
1for the volume of formaldehyde standard solution, ρ is the density of formaldehyde standard solution.
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| CN102331450A (en) * | 2011-03-25 | 2012-01-25 | 上海汶昌芯片科技有限公司 | Poisonous and harmful gas detection chip and preparation method thereof |
| CN103091371A (en) * | 2013-01-11 | 2013-05-08 | 江汉大学 | Detection method and detection device for content of formaldehyde in foods |
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| CN102331450A (en) * | 2011-03-25 | 2012-01-25 | 上海汶昌芯片科技有限公司 | Poisonous and harmful gas detection chip and preparation method thereof |
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