EP2100147A1 - Chemical indicator test strip - Google Patents

Chemical indicator test strip

Info

Publication number
EP2100147A1
EP2100147A1 EP07865691A EP07865691A EP2100147A1 EP 2100147 A1 EP2100147 A1 EP 2100147A1 EP 07865691 A EP07865691 A EP 07865691A EP 07865691 A EP07865691 A EP 07865691A EP 2100147 A1 EP2100147 A1 EP 2100147A1
Authority
EP
European Patent Office
Prior art keywords
chemical indicator
test strip
indicator test
acid
developing agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07865691A
Other languages
German (de)
English (en)
French (fr)
Inventor
Vinod P. Menon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Innovative Properties Co
Original Assignee
3M Innovative Properties Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US11/611,932 external-priority patent/US20080145940A1/en
Priority claimed from US11/611,926 external-priority patent/US20080145948A1/en
Application filed by 3M Innovative Properties Co filed Critical 3M Innovative Properties Co
Publication of EP2100147A1 publication Critical patent/EP2100147A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
    • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
    • B01L3/5023—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures with a sample being transported to, and subsequently stored in an absorbent for analysis
    • 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
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/52—Use of compounds or compositions for colorimetric, spectrophotometric or fluorometric investigation, e.g. use of reagent paper and including single- and multilayer analytical elements
    • G01N33/521—Single-layer analytical elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L2300/00—Additional constructional details
    • B01L2300/12—Specific details about materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L2300/00—Additional constructional details
    • B01L2300/16—Surface properties and coatings

Definitions

  • the present invention relates to chemical indicator test strips and to methods for the use of chemical indicator test strips for the detection and quantification of organic analytes.
  • Formulations that comprise medium chain length fatty acids and their esters, such as C 8 to C 12 fatty acid esters, are useful for the antimicrobial treatment of foods to reduce the number of food borne human pathogens in meats and to help protect plants from fungi and various pathogens that adversely effect the quality and the shelf life of fruits and vegetables.
  • antimicrobial lipids are typically more expensive than other antimicrobials (e.g., bleach, peroxide and/or weak organic acids), and, because of the expense, it is important to monitor, control and minimize their waste when used in the decontamination of food.
  • antimicrobials e.g., bleach, peroxide and/or weak organic acids
  • thermal paper as a colorimetric indicator for polar solvent vapor in air.
  • fully developed intensely colored thermal paper shows a decrease in color intensity on exposure to the vapor.
  • the decrease in intensity is proportional to the partial pressure of the vapor and is attributed to the disturbance of the hydrogen bonded network by the solvent vapors converting the colored quinoid dye to the colorless lactone form.
  • Dickert and coworkers (Anal. Chem. 1988, 60, 1377-1380) have spin-coated a mixture of the lactone dye and proton donor on quartz plates in conjunction with a transmissive optical detection system to serve as an optochemical sensor for low-boiling polar solvent vapors.
  • Test strips or indicator sticks are available to indicate the presence and concentration of an analyte in a liquid by immersing the strip or indicator stick into the liquid and observing the color change and color intensity. These products include the familiar litmus test for pH measurement as well as sophisticated tests for detecting clinically significant markers in biological fluids such as glucose or protein in blood and urine samples. Test strips or indicator sticks represent inexpensive single-use analytical tools that embody a high level of accuracy and can be used qualitatively with a visual comparator chart or in conjunction with a readout device for quantitative information and electronic record keeping.
  • test strip or indicator stick that is immersible in water and that is useful in the quantitative measurement and monitoring of water-miscible organic compounds.
  • the invention provides articles and methods for the detection and/or quantification of organic analytes.
  • the invention provides a chemical indicator test strip, comprising:
  • a coating comprising a leuco dye complex on the substrate, the coating being insoluble in water and reactive with an organic analyte, the coating derived from a solution of leuco dye and developing agent.
  • leuco dye refers to a dye whose molecules can acquire two forms, one of which is colorless.
  • Leuco dye complex refers to a complex comprised of one or more leuco dyes combined with one or more developing agents.
  • MIBK is an abbreviation for methyl isobutyl ketone.
  • the invention provides the foregoing chemical indicator test strip wherein the coating further comprises adjuvant, wherein the adjuvant is a water-insoluble, polar, hydrophobic, aprotic material that extends the lower limit of detection for the analyte than is otherwise attainable in the absence of such an adjuvant.
  • the adjuvant is a water-insoluble, polar, hydrophobic, aprotic material that extends the lower limit of detection for the analyte than is otherwise attainable in the absence of such an adjuvant.
  • the present invention provides a method of using a chemical indicator test strip, comprising: (a) Exposing a chemical indicator test strip to a liquid sample comprising an organic analyte in solution, the chemical indicator test strip, comprising:
  • a coating comprising a leuco dye complex on the substrate, the coating being insoluble in water and reactive with an organic analyte, the coating derived from a solution of leuco dye and developing agent; (b) Measuring a color change on the chemical indicator test strip following the exposing step;
  • Figure 1 is a plot of optical density v. concentration of n-propanol using chemical indicator test strips described in Example 1 herein;
  • Figure 2 illustrates plots of optical density v. concentration of (1) acetone and (2) propylene carbonate using chemical indicator test strips described in Example 3 herein;
  • Figure 3 is a plot of optical density v. concentration of n-propanol using chemical indicator test strips described in Example 4 herein;
  • Figure 4 is a plot of optical density v. concentration of n-propanol using chemical indicator test strips described in Example 5 herein;
  • Figure 5 is a plot of optical density v. time for chemical indicator test strips described in Example 6 herein using three different developing agents;
  • Figure 6 is a plot of optical density v. concentration of (1) propylene glycol and (2) n-propanol using chemical indicator test strips described in Example 7 herein;
  • Figure 7 is a plot of optical density v. concentration of n-propanol using chemical indicator test strips described in Example 9 herein;
  • Figure 8 is a plot of optical density v. concentration of n-propanol using chemical indicator test strips of Example 9 herein;
  • Figure 9 is a plot of optical density v. concentration of n-propanol for chemical indicator test strips of Example 10 herein;
  • Figure 10 is a plot of optical density v. concentration of propylene carbonate using chemical indicator test strips of Example 11 herein;
  • Figure 11 is a plot of optical density v. concentration for chemical indicator test strips of Example 13 herein;
  • Figure 12 is a plot of optical density v. concentration for chemical indicator test strips of Example 15 herein.
  • Embodiments of the present invention are described herein.
  • the invention provides a chemical indicator test strip and methods for the use of a chemical indicator test strip for the qualitative and quantitative monitoring of organic compounds.
  • Embodiments of the invention provide a colorimetric, immersible, chemical indicator test strip that can be used to rapidly and quantitatively determine the concentration of organic compounds in water or other solvents.
  • “chemical indicator test strips” and “test strips” are used interchangeably in reference to the articles of the present invention.
  • the inventive test strips comprise a substrate coated with a leuco dye complex capable of withstanding immersion in the solvent and particularly in aqueous systems.
  • the leuco dye complex is originally provided in a liquid indicator composition comprised of a leuco dye, a developing agent and optional additional components that enhance the performance of the test strip.
  • optional additional components are added to enhance the ability of the finished chemical indicator test strip to detect a particular analyte and/or to improve the sensitivity of the test strip at lower analyte concentrations.
  • the liquid indicator composition is coated onto the substrate and dried to provide a chemical indicator test strip according to the present invention.
  • Leuco dye complexes comprise at least one color-forming agent and at least one developing agent which, when combined, impart a non-white or colored appearance to the surface of the substrate of the chemical indicator test strip.
  • the leuco dye complex reverts or "bleaches" to an uncolored state in the presence of an organic analyte that is capable of solvating the develop agent.
  • the extent of the color change or bleaching is proportional to the concentration of the analyte in water so that, as the concentration of the organic analyte increases, the chemical indicator test strip becomes progressively lighter in color. With prior standardization, the degree to which the test strip changes color can be correlated with the concentration of the analyte.
  • the leuco dye complex useful in the chemical indicator test strips of the present invention comprise a color-forming agent and a developing agent.
  • suitable classes of leuco dyes include fluorans, rhodamines, and triarylmethane lactone leuco dyes. These compounds react with acidic developing agents, such as Lewis acids, salicylic acids, phenolic compounds, or acidic clays, to form highly colored species by the opening of a lactone ring.
  • acidic developing agents such as Lewis acids, salicylic acids, phenolic compounds, or acidic clays
  • leuco dye crystal violet lactone (a triarylmethane lactone). In its lactone form, crystal violet lactone is colorless or slightly yellow. But, in a low pH environment, it becomes protonated and exhibits an intensely violet color.
  • leuco dyes are suitable for use herein, either individually or in combinations of two or more: acyl auramines acylleucophenothiazines alpha-unsaturated aryl ketones azaphthalides benzoyl leuco methylene blue benzoyl leuco oxazine benzoyl leuco thiazine beta-unsaturated aryl ketones basic mono azo dyes bisindolylphthalide
  • Developing agents are included in the leuco dye complexes of the invention. Such developing agents are often referred to as electron acceptors but are more accurately described as proton donors.
  • the developing agent is water insoluble.
  • the developing agent is a weak acid selected from, octyl p-hydroxybenzoate, methyl />-hydroxybenzoate, 1,2,3-triazoles, 4-hydroxycoumarin derivatives, and combinations of two or more of the foregoing.
  • Lewis acids may be used as developing agents in the leuco dye complexes discussed herein.
  • developing agents include activated clay substances, such as attapulgite, acid clay, bentonite, montmorillonite, acid-activated bentonite or montmorillonite, zeolite, hoalloysite, silicon dioxide, aluminum oxide, aluminum sulfate, aluminum phosphate, hydrated zirconium dioxide, zinc chloride, zinc nitrate, activated kaolin or other clay.
  • acidic, organic compounds are useful as developing agents.
  • developing agents include ring-substituted phenols, resorcinols, salicylic acids (e.g., 3,5-bis( ⁇ , ⁇ '- dimethylbenzyl)salicylic; 3,5- bis(( ⁇ -methylbenzyl)salicylic acid), or salicyl acid esters and metal salts thereof (e.g., zinc salts).
  • Additional acidic, organic compounds include certain polymeric materials such as, for example, a phenolic polymer, an alkylphenolacetylene resin, a maleic acid/colophonium resin or a partially or fully hydrolyzed polymer of maleic anhydride with styrene, ethylene or vinyl methyl ether, or carboxymethylene. Mixtures of two or more of the monomeric and polymeric acidic, organic compounds may also be used.
  • developing agents may be selected from phenolic resins or phenolic compounds such as 4-tert-butylphenol; 4- phenylphenol; methylene-bis(p- phenylphenol); 4-hydroxydiphenyl ether; alpha-naphthol; beta- napthol; methyl A- hydroxybenzoate; benzyl 4-hydroxybenzoate; 4-hydroxydiphenyl sulfone; A- hydroxyacetophenone; 2,2'-dihydroxydiphenyl; 4,4'-cyclohexylidenephenol; 4,4'- isopropylidenediphenol; 4,4-isopropylidenebis(2-methylphenol); a pyridine complex of zinc thiocyanate; 4,4-bis(4-hydroxyphenyl)valeric acid; hydroquinone; pyrogallol; phoroglucine; p- hydroxybenzoic acid; m- hydroxybenzoic acid; o-hydroxybenzoic acid; gallic
  • the developing agent is poly(4-vinyl phenol). In other embodiments the developing agent is 4,4'-(9-fluorenylidene)-diphenol.
  • the leuco dye complex is optionally formulated with at least one adjuvant in the form of a water-insoluble, polar, hydrophobic, aprotic component.
  • polar refers to the ability of the material to form hydrogen bonds.
  • the polar, hydrophobic, aprotic adjuvant has a low vapor pressure (e.g., 0.1mm Hg).
  • An adjuvant when present, is added to an initial liquid indicator composition along with the leuco dye complex.
  • the liquid indicator composition may then be applied to a substrate and dried to provide a chemical indicator test strip with an improved analytical range.
  • the presence of an adjuvant improves the sensitivity of the chemical indicator test strip at lower analyte concentrations, extending the lower limits of detectability for a particular organic analyte.
  • Inclusion of an adjuvant in the chemical indicator test strips of the invention is most typically desired where the detection of a particular analyte at lower concentrations is desired because the detection limit for an organic analyte is much lower in the presence of an adjuvant than would otherwise be achievable in the absence of such an adjuvant.
  • an adjuvant can extend the analytical range down to about 0.2 % by weight of analyte in water.
  • the adjuvant compound typically is selected from compounds that will not confer color to the leuco dye. Representative and suitable compounds from this class include aliphatic esters and aromatic esters of carboxylic acids such as those selected from citrates, phthalates, adipates, benzoates, azelates, and mellitates.
  • the adjuvant is selected from organic phosphates, organic sulfonates , and sulfonamides. In other embodiments, adjuvants with a large number (e.g., greater than three) of polar functionalities per molecule are preferred. In still other embodiments, the adjuvant is selected from citrates and sulfonamides.
  • the chemical indicator test strip of the invention comprises a coating having a leuco dye complex associated with surfactant.
  • one or more surfactant is included in an initial liquid indicator composition applied to a substrate. Once dried, the resulting coating comprises the leuco dye complex and surfactant.
  • One or more surfactants may be included with the dye complex in order to facilitate wetting of the substrate in an aqueous environment and as an aid in the transport of an organic analyte into the chemical indicator test strip and in association with the leuco dye complex thereon. Suitable surfactants may be selected from compounds that will not confer color in association with the leuco dye.
  • surfactant may be included in a coatable liquid indicator composition with a leuco dye complex to be coated onto a substrate.
  • the inclusion of surfactant may be desired for certain organic analytes.
  • the detection, monitoring and/or quantification of antimicrobial fatty acid monoesters in water is enhanced by the presence of surfactant in the chemical indicator test strips of the invention.
  • antimicrobials may, for example, be used in the antimicrobial treatment of food items to prevent contamination by pathogens.
  • the fatty acid monoesters may be provided to a user in the form of a concentrated composition comprising, for example, between about 1.0 - 50.0 wt. % of the monoester.
  • the concentrate Prior to the application of the monoester to food, however, the concentrate can be diluted with water to provide a diluted and ready-to-use fatty acid monoester formulation having a monoester concentration of between about 0.001 and 5.0 wt. % and, in some embodiments, between about 0.005 and 1.0 wt. %.
  • one or more surfactants may be included in the liquid indicator composition of the leuco dye complex that is coated onto a substrate.
  • the coating process and related formulation of the liquid composition are described elsewhere herein.
  • the use of a chemical indicator test strip according to the present invention for the detection of certain fatty acid esters such as Cs to C12 fatty acid esters, typically can be made without including an adjuvant to detect the ester in a ready- to-use formulation within the ester concentration ranges recited herein.
  • the present invention provides, in part, a method for the detection and quantification of fatty acid monoesters using the chemical indicator test strips described herein.
  • Fatty acid monoesters detectable using the chemical indicator test strips of the invention include one or more fatty acid esters of a polyhydric alcohol, a fatty ether of a polyhydric alcohol, alkoxylated derivatives thereof (of either the ester or the ether), and combinations of two or more of the foregoing.
  • Such compositions include an antimicrobial component that includes a fatty alcohol ester of a hydroxyacid, alkoxylated derivatives thereof, or combinations thereof.
  • an effective amount of an antimicrobial component (typically, an antimicrobial lipid component) comprise a (C 7 -Ci 4 )saturated fatty alcohol monoester of a (C 2 -C 8 ) hydroxycarboxylic acid, a (Cs-C 22 )mono- or polyunsaturated fatty alcohol monoester of a (C 2 -C 8 ) hydroxycarboxylic acid, an alkoxylated derivative of either of the foregoing, or combinations thereof, wherein the alkoxylated derivative has less than 5 moles of alkoxide per mole of hydroxycarboxylic acid.
  • Suitable surfactants may be selected from any of the four primary groups; anionic, cationic, non-ionic, and zwitterionic (amphoteric).
  • Exemplary surfactants suitable for use in the invention include those illustrated in the Examples herein.
  • Exemplary cationic surfactants include, but are not limited to, salts of optionally polyoxyalkylenated primary, secondary, or tertiary fatty amines; quaternary ammonium salts such as tetraalkylammonium, alkylamidoalkyltrialkylammonium, trialkylbenzylammonium, trialkylhydroxyalkylammonium, or alkylpyridinium having compatible anionic counterions such as halides (preferably chlorides or bromides) or alkyl sulfates such as methosulfate or ethosulfate as well as other anionic counterions; imidazoline derivatives; amine oxides of a cationic nature (e.g., at an acidic pH).
  • quaternary ammonium salts such as tetraalkylammonium, alkylamidoalkyltrialkylammonium, trialkylbenzylammonium, trialkylhydroxyalkylammonium,
  • the surfactant(s) comprise one or more cationic surfactants selected from the group consisting of tetralkyl ammonium, trialkylbenzylammonium, and alkylpyridinium halides, and mixtures thereof.
  • amine oxide surfactants may be used such as those including alkyl and alkylamidoalkyldialkylamine oxides.
  • amine oxide surfactants include those commercially available from Stepan Company under the trade designations AMMONYX LO, AMMONYX LMDO, and AMMONYX CO, which are lauryldimethylamine oxide, laurylamidopropyldimethylamine oxide, and cetyl amine oxide.
  • anionic surfactant(s) may be used including, but are not limited to, sarcosinates, glutamates, alkyl sulfates, sodium or potassium alkyleth sulfates, ammonium alkyleth sulfates, ammonium laureth-n-sulfates, laureth-n-sulfates, isethionates, alkyl and aralkyl glycerylether sulfonates, alkyl and aralkyl sulfosuccinates (e.g.
  • anionic surfactants may have a metal or organic ammonium counterion.
  • the anionic surfactants useful in the compositions of the present invention are selected from the group consisting of sulfonates, sulfates, phosphates, phosphonates and combinations of two or more of the foregoing.
  • Suitable sulfonates and sulfates include alkyl sulfates, alkyl ether sulfates, alkyl sulfonates, alkylether sulfonates, alkylbenzene sufonates, alkylbenzene ether sulfates, alkylsulfoacetates, secondary alkane sulfonates, secondary alkylsulfates, and the like.
  • Commercially available alkyl ether sulfonates such as lauryl ether sulfates are available under the trade designation POLYSTEP B 12 and POLYSTEP B22 available from Stepan Company.
  • anionic surfactants include sodium methyl taurate (available under the trade designation NIKKOL CMT30 from Nikko Chemicals Co., Tokyo, Japan); secondary alkane sulfonates such as Hostapur SAS which is sodium (C 14 - Cn) secondary alkane sulfonates (alpha-olefin sulfonates) available from Clariant Corp., Charlotte, N.C.; methyl-2-sulfoalkyl esters such as sodium methyl-2-sulfo(C12- 16)ester and disodium 2-sulfo (C 12 - C ⁇ ) fatty acid available from Stepan Company under the trade designation ALPHASTEP PC-48; alkylsulfoacetates and alkylsulfosuccinates available as sodium laurylsulfoacetate (under the trade designation LANTHANOL LAL) and disodiumlaurethsulfosuccinate (STEP ANMILD SL3), both from Stepan Company;
  • Suitable phosphates and phosphonates include alkyl phosphates, alkylether phosphates, aralkylphosphates, and aralkylether phosphates.
  • Such surfactants may include a mixture of mono-, di- and tri-(alkyltetraglycolether)-o-phosphoric acid esters generally referred to as trilaureth-4-phosphate commercially available under the trade designation HOSTAPHAT 340KL from Clariant Corp., as well as PPG-5 ceteth 10 phosphate available under the trade designation CRODAPHOS SG from Croda Inc., Parsipanny, N.J., and mixtures thereof.
  • amphoteric surfactants may be used and include surfactants having tertiary amine groups, which may be protonated, as well as quaternary amine containing zwitterionic surfactants.
  • Useful amphoteric surfactants include without limitation ammonium carboxylate amphoterics as well as ammonium sulfonate amphoterics.
  • Examples of ammonium carboxylate amphoteric surfactants include, but are not limited to: certain betaines such as cocobetaine and cocamidopropyl betaine
  • MACKAM CB-35 and MACKAM L from Mclntyre Group Ltd., University Park, 111.
  • monoacetates such as sodium lauroamphoacetate
  • diacetates such as disodium lauroamphoacetate
  • amino- and alkylamino-propionates such as lauraminopropionic acid
  • MACKAM IL, MACKAM 2L, and MACKAM 151 L respectively, from Mclntyre Group Ltd.
  • ammonium sulfonate amphoterics often referred to as “sultaines” or “sulfobetaines,” include cocamidopropylhydroxysultaine (commercially available as MACKAM 50-SB from Mclntyre Group Ltd.).
  • the sulfoamphoterics may be preferred over the carboxylate amphoterics since the sulfonate group will remain ionized at much lower pH values.
  • nonionic surfactants may be used which include, but are not limited to, alkyl glucosides, alkyl polyglucosides, polyhydroxy fatty acid amides, sucrose esters, esters of fatty acids and polyhydric alcohols, fatty acid alkanolamides, ethoxylated fatty acids, ethoxylated aliphatic acids, ethoxylated fatty alcohols (e.g., octyl phenoxy polyethoxyethanol available under the trade name TRITON X-IOO and nonyl phenoxy poly(ethyleneoxy) ethanol available under the trade name NONIDET P-40, both from Sigrna, St.
  • alkyl glucosides alkyl polyglucosides
  • polyhydroxy fatty acid amides sucrose esters, esters of fatty acids and polyhydric alcohols
  • fatty acid alkanolamides ethoxylated fatty acids
  • ethoxylated aliphatic acids e
  • ethoxylated and/or propoxylated aliphatic alcohols e.g., that available under the trade name BRIJ from ICI
  • ethoxylated glycerides ethoxylated/propoxylated block copolymers such as the PLURONIC and TETRONIC surfactants available from BASF
  • ethoxylated cyclic ether adducts ethoxylated amide and imidazoline adducts
  • ethoxylated amine adducts ethoxylated mercaptan adducts
  • ethoxylated condensates with alkyl phenols ethoxylated nitrogen-based hydrophobes
  • ethoxylated polyoxypropylenes polymeric silicones
  • fluorinated surfactants e.g., those available under the trade names FLUORAD-FS 300 from Minnesota Mining and Manufacturing Co., St.
  • nonionic surfactants useful in the compositions of the present invention are selected from the group consisting of Poloxamers such as PLURONIC from BASF, sorbitan fatty acid esters, and mixtures thereof. It will be understood that the foregoing surfactants can be used individually or in combination of two or more of the foregoing.
  • the foregoing dye complex is coated onto a substrate to provide an indicator test strip according to the invention.
  • the substrate material can include cellulosic and non-cellulosic materials such as, for example, paper, natural or synthetic fibers, threads and yarns made from materials such as cotton, rayon, hemp, jute, bamboo fibers, cellulose acetate, carboxymethylated solvent-spun cellulose fibers and the like.
  • the substrate may comprise material selected from polyester, polyamide, polyacrylamide, polyacetate, polyacrylics, polyolefin (e.g., polypropylene polyethylene, ethylene propylene copolymers, and ethylene butylene copolymers), polyurethane (including polyurethane foams), vinyl (e.g., polyvinylchloride), polystyrene, fiberglass, ceramic fiber, glass, silicon dioxide, polyacrylate, polyacrylonitrile, polyvinylidene difluoride, polytetrafluoroethylene, polyoxymethylene, polyvinyl alcohol, polylactic acid, polyvinyl ether, polyvinylpyrrolidone, polycarbonate, styrene-ethylenebutylene-styrene elastomer, styrene-butylene-styrene elastomer, styrene- isoprene-styrene elastomer, and combinations of two or more
  • the substrate can be porous or nonporous, and the dye complex can be coated onto a surface of the substrate or impregnated into it, for example.
  • the substrate may be flexible and can comprise woven or nonwoven materials made of natural or synthetic compounds.
  • the substrate may be a polymeric web (non-woven or woven), a polymer film, a hydrocolloid, a foam material, a metallic foil, paper, and/or combinations of two or more of the foregoing.
  • the substrate can be an absorbent cotton gauze or a cotton swab, for example.
  • the substrate is glass, such as a glass slide, for example.
  • Suitable porous materials for use as substrates in embodiments of the invention include paper, knits, wovens (e.g., cheese cloth and gauze), nonwovens (including spun- bonded nonwovens, and BMF (blown micro fibers), extruded porous sheets, and perforated sheets.
  • a liquid indicator composition is applied to a suitable substrate and dried.
  • the preparation of a chemical indicator test strip includes preparing a coatable liquid indicator composition that can be applied to the substrate.
  • the liquid indicator composition is prepared by adding at least one leuco dye and at least one developing agent to a solvent. Additional components for the indicator composition include the aforementioned adjuvant and/or the surfactant.
  • the components of the coatable liquid indicator composition may be added to the solvent in any order and mixed to ensure dissolution of the components in the solvent.
  • the liquid indicator composition comprises a leuco dye and, optionally, an adjuvant in a suitable solvent such as, for example, MIBK or methyl isobutyl ketone.
  • concentrations of the individual components can vary within the scope of the invention. In some embodiments, the concentration of leuco dye is within the range between about 0.02% and about 2.0% by weight. In other embodiments, the leuco dye is within the range between about 0.05% and about 1.0% by weight. In still other embodiments, the concentration of leuco dye is within the range between about 0.1% and about 0.3% by weight.
  • the liquid indicator composition comprises developing agent.
  • the concentration of developing agent is within the range between about 0.2% and about 20% by weight. In other embodiments, the developing agent is within the range between about 0.5% and about 10% by weight. In still other embodiments, the concentration of developing agent is within the range between about 1% and about 3% by weight.
  • the weight ratio between the leuco dye and the developing agent can range from about 10/1 to about 1/100. In some embodiments, the weight ratio between the leuco dye and the developing agent can range from about 5/1 to about 1/20. In still other embodiments, the weight ratio between the leuco dye and the developing agent can range from about 1/1 to about 1/10.
  • the concentration of adjuvant is within the range between about 0.2% and about 20% by weight. In other embodiments, the adjuvant is within the range between about 0.5% and about 10% by weight. In still other embodiments, the concentration of adjuvant is within the range between about 1% and about 3% by weight. In these embodiments, the weight ratio between the leuco dye and the adjuvant can range from about 10/1 to about 1/100. In some embodiments, the weight ratio between the leuco dye and the adjuvant can range from about 5/1 to about 1/20. In still other embodiments, the weight ratio between the leuco dye and the adjuvant can range from about 1/1 to about 1/10.
  • the concentration of surfactant is within the range between about 0.04% and about 4% by weight. In other embodiments, the surfactant is within the range between about 0.08% and about 2% by weight. In still other embodiments, the concentration of surfactant is within the range between about 0.2% and about 0.6% by weight.
  • the weight ratio between the leuco dye and the surfactant can range from about 5/1 to about 1/5. In some embodiments, the weight ratio between the leuco dye and the surfactant can range from about 3/1 to about 1/3. In still other embodiments, the weight ratio between the leuco dye and the surfactant can range from about 2/1 to about 1/2.
  • the process for preparing a chemical indicator will include the selection of the substrate.
  • the available surface area and absorptive characteristics of a material can be a factor in selecting a suitable substrate.
  • a porous material may provide a substrate with more surface area on which to coat the indicator composition.
  • the surface area and absorptive characteristics of the substrate will also be a factor in how readily the organic analyte may be introduced for solvation with the dried leuco dye complex.
  • a non-absorbent material may be preferred over an absorbent material because the dried leuco dye is more readily maintained on the outermost surface of the non-absorbent substrate.
  • the dried dye complex may be more readily available to form hydrogen bonds with an organic analyte when the chemical indicator test strip of the invention is used for monitoring a particular aqueous environment.
  • a non- absorbent material with at least some degree of porosity may be advantageously used as substrate in order to increase the total surface area of the substrate that is available to be coated with a leuco dye complex.
  • the process of applying the liquid indicator composition to the substrate requires the deposition of a sufficient quantity or volume of the liquid indicator composition to wet at least one surface of the substrate.
  • a suitable amount or volume of the liquid indicator composition includes any amount or volume which, when dried, provides a dye-covered surface.
  • the dye covered surface will be of sufficient area to allow for the representative sampling of an aqueous system or the like.
  • the surface area of the coated substrate will desirably be large enough an area so that color changes thereon will be readily detectable by an electronic detector, such as a densitometer or the like.
  • a light or thin coating of indicator composition may be preferred in order to provide a finished article with a dye complex closely associated with the outer surface of the substrate.
  • the actual wet coating weights of the liquid indicator composition that is applied to the substrate can vary depending on the dye indicator and other components that are selected for inclusion in the finished article, the material chosen for a substrate, the coatable surface area of the selected substrate, and the like.
  • the determination of an appropriate coating weight for the indicator composition on a substrate is within the skill of those practicing in the field without undue experimentation.
  • the liquid indicator composition forms a colored coating on the substrate and the resulting article may be used as a chemical indicator test strip according to the present invention. Drying may be accomplished by any suitable means. In some embodiments, drying is accomplished by placing the wetted substrate in an oven or the like at an elevated temperature for sufficient time to drive off solvent and to provide a dried article suitable for use as described herein. In some embodiments, the wetted substrate is dried at ambient or room temperature by simply allowing the solvent to evaporate. In other embodiments, the wetted substrate may be placed in an oven for a short time (e.g., several minutes) at an elevated temperature (e.g., 150 0 F or 66°C). Once dried, the resulting article is available for use as a chemical indicator test strip.
  • drying is accomplished by placing the wetted substrate in an oven or the like at an elevated temperature for sufficient time to drive off solvent and to provide a dried article suitable for use as described herein. In some embodiments, the wetted substrate is dried at ambient or room temperature by simply allowing the solvent to evaporate
  • the chemical indicator test strips of the invention provide a non-specific analytical tool to detect the presence of organic analytes in a solvent (e.g., water).
  • a solvent e.g., water
  • the chemical indicator test strips of the invention provide a convenient and rapid means for monitoring an organic analyte, qualitatively and/or quantitatively.
  • the chemical indicator test strips of the invention may be used in monitoring any of a variety of processes to detect and/or measure the amount of any of a variety of organic analytes in an aqueous formulation, process stream, bath or the like.
  • the chemical indicator test strip is simply immersed into the process stream or other liquid in which the analyte may be present.
  • the indicator test strips may be immersed within the liquid sample and mildly agitated for a sufficient amount of time to adequately wet the strip (e.g., 10-20 seconds).
  • Upon removal of the test strip from the liquid it may be blotted with a paper towel or the like using gentle pressure to remove excess liquid.
  • the presence of an analyte may be detected visually by observing a color change to the test strip, typically by observing a lightening in the color of the dye complex on the substrate. If needed, the test strip may be compared to a 'control' strip having the initial or starting color of the dye complex prior to immersion and exposure to an organic analyte.
  • the qualitative determination of the presence of an organic analyte is more readily apparent by electronically comparing the color of the test strip before and after its immersion in a testing environment to determine whether a color change has occurred.
  • a densitometer for example, may be useful in the determination of a color change by measuring the optical density of the exposed test strip relative to an unexposed test strip.
  • the chemical indicator test strips of the invention are used qualitatively in determining the presence of an organic analyte as well as being used quantitatively to determine the concentration of the organic analyte.
  • a standardization curve is prepared to provide a standard relationship between optical density and analyte concentration. Such a standardization curve may be based on a prepared set of standard solutions that resemble the expected chemical make-up of the stream, bath or compositions that are to be monitored. Standard analyte solutions typically will be made to cover the range of analyte concentrations that might reasonably be expected for the process that is being monitored.
  • a standardization plot of optical density v. analyte concentration may then be established. Thereafter, optical density readings on samples obtained in a monitoring process can be compared against the standardization plot to determine a concentration of analyte in a sample based on a measurement of the optical density for a chemical indicator test strip.
  • the standard compositions used to determine the standard curve are preferably similar to or substantially chemically the same as the compositions of the expected samples.
  • the amount of time that any of the test strips are exposed to an analyte process stream or the like ought to be substantially the same from one sample to the next and the same for the samples as for the standard solutions.
  • the chemical indicator test strips of the invention are capable of detecting organic analytes in a composition, process stream or the like at analyte concentrations in the range from about 0% to about 50% by weight. In some embodiments, the detection limits for certain organic analytes ranges from about 0% to about 25% by weight.
  • Example 1 Construction of an indicator strip with a substantially water-insoluble quinoid dye complex
  • MIBK methyl isobutyl ketone
  • Blank indicator strips were prepared by heat bonding a 0.3" by 0.3" swatch of Whatman 114 filter paper (obtained from Whatman International, England) to one end of a 4" by 0.3" polyester strip (5mils thick) using a supported double-sided PSA. Five microliters of the solution were spotted on the paper. The initially colorless spot turned deep blue on evaporation of the MIBK. The chemical indicator test strip was dried at 150 0 F for 1 minute, and cooled.
  • Comparative Example 1 construction of an indicator strip from a dye complex with a water soluble developing agent - bisphenol-A
  • MIBK methyl isobutyl ketone
  • Blank chemical indicator test strips were prepared by heat bonding a 0.3" by 0.3" swatch of Whatman 114 filter paper (obtained from Whatman International, England) to one end of a 4" by 0.3" polyester strip (5mils thick) using a supported double-sided PSA. Five microliters of the solution were spotted on the paper. The initially colorless spot turned deep blue on evaporation of the MIBK. The indicator strip was dried at 150 0 F for 1 minute, and cooled.
  • Aqueous solutions of n-propanol (obtained from Aldrich Chemicals) were prepared in a range of concentrations from 0% w/w to 14% w/w.
  • Chemical indicator test strips of the type described in Example 1 were prepared and immersed with mild agitation in these solutions for 15 seconds each. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer using the green filter setting. A gradual decrease in color intensity could be visually distinguished with an increase in propanol concentration.
  • Example 3 use of the indicator in Example 1 for low vapor pressure and high vapor pressure solvents
  • Aqueous solutions of acetone and propylene carbonate (both obtained from Aldrich Chemicals) were prepared in a range of concentrations from 0%w/w/ to 14%w/w.
  • Chemical indicator test strips of the type described in Example 1 were prepared and immersed with mild agitation in these solutions for 15 seconds each. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer using the green filter setting. A gradual decrease in color intensity could be visually distinguished with an increase in solvent concentration.
  • Example 4 Construction and use of an indicator with a different lactone dye
  • Aqueous solutions of n-propanol were prepared in a range of concentrations from 0%w/w/ to 16%w/w.
  • Chemical indicator test strips of the type described above were prepared and immersed with mild agitation in these solutions for 15 seconds each. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer. A gradual decrease in color intensity could be visually distinguished with an increase in solvent concentration.
  • the results are graphically represented in Figure 3 below.
  • the chemical indicator test strip comprising a blue dye (see Figure 1)
  • the chemical indicator test strip made with red dye also displayed a linear region of optical density change with concentration. However, the blue indicator has shown a lower linear detection limit (6%) compared with the red indicator (10%).
  • Example 5 construction and use of an indicator with 4,4'-(9-fluorenylidene)- diphenol as hydrophobic developing agent
  • Blank indicator strips were prepared by heat bonding a 0.3" by 0.3" swatch of Whatman 114 filter paper (obtained from Whatman International, England) to one end of a 4" by 0.3" polyester strip (5 mils thick) using a supported double-sided PSA. Five microliters of the solution were spotted on the paper. The initially colorless spot turned deep blue on evaporation of the
  • the chemical indicator test strip was dried at 150 0 F for 1 minute, and cooled prior to use.
  • Aqueous solutions of n-propanol were prepared in a range of concentrations from 0%w/w/ to 16%w/w.
  • Chemical indicator test strips of the type described above were immersed with mild agitation in the n-propanol solutions for 15 seconds each. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer. A gradual decrease in color intensity could be visually distinguished with an increase in solvent concentration.
  • the results are graphically represented in Figure 4 which displays a linear region of optical density changing with concentration..
  • Example 6 Comparison of water stability of the indicators from Example 1, Comparative Example 1, and Example 5
  • Comparative Example 1 and Example 5 were immersed in an aqueous solution of 12% n- propanol for different lengths of time ranging from 15 seconds to 20 minutes. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer. The results are shown graphically in Figure 5, showing that chemical indicator test strips prepared with substantially water-insoluble developing agents show extremely good solution stability, while the leuco dye complex in the chemical indicator test strip constructed using bisphenol A, a hydrophilic developing agent, quickly degrades in water. Additionally, the chemical indicator test strip using bisphenol-A as a developing agent went from a blue color to becoming almost colorless on immersion, while the other chemical indicator test strips retained their color.
  • Aqueous solutions of n-propanol and propylene glycol were prepared in a range of concentrations from 0%w/w/ to 16%w/w.
  • Chemical indicator test strips of the type described in Example 1 were prepared and immersed in these solutions for 15 seconds each under mild agitation. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer. A gradual decrease in color intensity could be visually distinguished with an increase in solvent concentration for the propanol solutions. No change in optical density was observed even at the highest concentration of propylene glycol employed.
  • Example 8 Construction of an indicator strip with a substantially water-insoluble leuco dye complex and a water-insoluble adjuvant
  • leuco dye Pergascript Blue I-2RN obtained from Ciba-Geigy Specialty Chemicals, NC was dissolved in 2.5grams of methyl isobutyl ketone (MIBK) obtained from Aldrich Chemicals.
  • MIBK methyl isobutyl ketone
  • 200 milligrams of developing agent poly(4- vinyl phenol), M.W. 8000Da (obtained from Aldrich Chemicals)and 200 milligrams of adjuvant acetyltributyl citrate (Citroflex A-4 by Moreflex Inc., NC) were dissolved in 5 grams MIBK.
  • Blank chemical indicator test strips were prepared by heat bonding a 0.3" by 0.3" swatch of Whatman 114 filter paper (obtained from Whatman International, England) to one end of a 4" by 0.3" polyester strip (5mils thick) using a supported double-sided PSA. Five microliters of the solution were spotted on the paper. The initially colorless spot turned deep blue on evaporation of the MIBK. The chemical indicator test strip was dried at 150 0 F for 1 minute, and cooled.
  • This example demonstrates the construction of an indicator strip with a substantially water-insoluble quinoid dye complex and a water-insoluble non-polar aprotic compound.
  • Twenty milligrams of Pergascript Blue I-2RN was dissolved in 2.5 grams of methyl isobutyl ketone (MIBK).
  • MIBK methyl isobutyl ketone
  • TN TN
  • MIBK Magnetic Ink-Kinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinskyinsky
  • Aqueous solutions of n-propanol (obtained from Aldrich Chemicals) were prepared in a range of concentrations from 0%w/w/ to 14%w/w.
  • Chemical indicator test strips of the type described in Example 8 were prepared and immersed with mild agitation in these solutions for 15 seconds each. Each strip was then removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer using the green filter setting. A gradual decrease in color intensity could be visually distinguished with an increase in propanol concentration.
  • the results are graphically represented in Figure 7 showing a linear dependence of the optical density on concentration in the entire analyte concentration range.
  • Example 10 Construction and use of a chemical indicator test strip with a different hydrophobic polar aprotic chemical
  • Example 11 use of the indicator in Example 8 with a propylene carbonate analyte
  • Aqueous solutions of propylene carbonate (Aldrich Chemicals) were prepared in a range of concentrations from 0%w/w/ to 12%w/w.
  • Chemical indicator test strips of the type described in Example 8 were prepared and immersed with mild agitation in the propylene carbonate solutions for 15 seconds each. Each strip was removed from solution, quickly blotted using gentle pressure on an absorbent paper towel, and the optical density immediately measured on a MacBeth RD917 densitometer using the green filter setting. A gradual decrease in color intensity could be visually distinguished with an increase in propylene carbonate concentration.
  • the results are graphically represented in Figure 10 where the linear dependence of optical density on concentration extends down to near 0% analyte in water.
  • Aqueous acid solutions of a mixture of propylene glycol monocaprylate (Abitec, 99% purity, FCC grade) and dioctylsulfosuccinate (Cytec, FCC grade) in the weight ratio 98:2 were prepared in a range of concentrations from 0%w/w/ to l%w/w and used as analyte solutions.
  • the solution was 0.25% in lactic acid and 0.25% in malic acid (Brenntag, FCC grade).
  • Chemical indicator test strips of the type described in Example 12 were prepared and spotted with 40 microliters of the analyte solutions over the indicator area. Each strip was then developed at room temperature for ten minutes and dried at 150 0 F for five minutes. The optical density of the chemical indicator test strips was measured on a MacBeth RD917 densitometer using the red filter setting under null density conditions. A gradual decrease in color intensity could be visually distinguished with an increase in ester concentration. The results are graphically represented in Figure 11 showing that the optical density of the chemical indicator test strip is linearly dependent on the aqueous concentration of the monoester with a large response per unit concentration change.
  • MIBK Aldrich Chemicals
  • the two solutions were mixed together to obtain a clear homogenous solution.
  • Blank chemical indicator test strips were prepared from blotting paper # 703 obtained from VWR Scientific, PA. Five microliters of the solution were spotted on the paper. The initially colorless spot turned deep blue on evaporation of the MIBK. The indicator strip was dried at 150 0 F for 10 minutes, and cooled.
  • Example 15 Aqueous acid solutions of a mixture of propylene glycol monocaprylate (Abitec, 99% purity, FCC grade) and dioctylsulfosuccinate (Cytec, FCC grade) in the weight ratio 98:2 were prepared in a range of concentrations from 0%w/w/ to l%w/w. The solution was 0.25% in lactic acid and 0.25% in malic acid (Brenntag, FCC grade). Chemical indicator test strips of the type described in Example 13 were prepared and spotted with 40 microliters of the test solution over the indicator area. Each strip was then developed at room temperature for ten minutes and dried at 150 0 F for five minutes. The optical density of the strips was measured on a MacBeth RD917 densitometer using the red filter setting under null density conditions. A very gradual decrease in color intensity could be visually distinguished with an increase in ester concentration. The results are graphically represented in Figure 12.

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