JPH0348151A - Surface-active agent detecting electrode for potential difference titration - Google Patents

Abstract

PURPOSE: To shorten the time required for analyzing a surfactant material by employing a conductive core member and a semipermeable membrane for coating the core member wherein the semipermeable membrane contains a polymer, a plasticizer and an ion exchange material of DMB-DSB at a specified ratio. CONSTITUTION: An electrode 11 for detecting anion, cation, nonion and an amphoteric surfactant is disposed, along with a reference electrode 14, in a container 13 containing a sample surfactant solution to be titrated. The end parts of the electrodes 11, 14 projecting over the liquid level are connected electrically through an electric unit 27 indicating the voltage on the electrode. The detection electrode 11 is a coated wire electrode comprising a conductive core member 31 having a part coated with a semipermeable membrane 35. The semipermeable membrane 35 comprises a semipermeable matrix containing a polymer, a plasticizer and an ion exchange material of DMB-DSB at an appropriate ratio sensitive for the surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to sensing electrodes for titration, and more particularly to sensing electrodes for potentiometric titration of surfactants in solution.

Very often it is desirable to detect the concentration of surfactants in a solution. For example, during the manufacture of commercial detergents it is necessary to test the concentration of surfactants in solutions to maintain their quality and determine product stability. Similar quantitative testing of the raw materials from which commercial detergents are made is required.

During the formulation of new surfactant compounds and the advancement of new applications of surfactants, analytical testing of surfactant concentrations is usually required.

A semi-standard assay for anionic and cationic active detergents in solution is a two-phase nibton (Epton) titration. Bromocresol green, methylene blue and dimidium bromide-disulfine blue are commonly used to determine the stoichiometric endpoint in such titrations.
,um bromide-and5ulphine blue
Three colorimetric indicators are used: e=:=DMB-DSB).In the case of non-ionic surfactants, a common two-phase Ebd titration is not possible, an alternative titration technique is 5. Still other alternative techniques and 11. Requiring 112-dikuDO ethane, which is harmful to health. Quantitative analysis of nonionic surfactants is performed using high pressure liquid chromatography (HPLC) equipment, but this also requires relatively complicated sample preparation and hazardous solvents.

In view of the shortcomings of two-phase titrations of surfactants, researchers in the art have attempted to devise potentiometric methods to perform the assay. In potentiometric cells for detecting the concentration of surfactant molecules, it is known to use ion-selective thin film electrodes to control ion transfer between a reference solution and a sample solution to be calibrated. The membrane may be formed from, for example, an ion-selective glass material, an ion-selective polymeric material, or an ion-selective water-miscible liquid. In potentiometric titration, a titrant is added to a sample solution in an electrochemical cell and combines with the ions in the solution. When the titrant is properly selected, the change in the cell's tetraelectricity is relatively noticeable at the end of the titration. By potentiometrically monitoring the e, m, f of the cell during the titration, the inflection point on the titration curve can be identified, which generally represents the end point, and in direct potentiometric methods, the indicator and During the titration, e, m, f with respect to the reference electrode are measured in °C by means of a suitable electrometer. However, a drawback of conventional potentiometric titrations is that the indicator electrode typically responds only to closely related congeners of the ion exchange material trapped in the membrane of the electrode. Additionally, conventional indicator electrodes are responsive to either cationic or anionic surfactants, but not to both1, and therefore, the indicator electrode for potentiometric titrations is usually responsive to the type of surfactant being titrated. They must be carefully matched and exchanged when titrating different types of surfactants. For the general operation of coated wire whisperers with r-on selectivity and their application to various analytical problems involving anionic, ionic or cationic organic species, see At+alytica Chimi.
iL in caActq (1986) 271-279,
Cunningham and H.

Fracie discusses. U.S. Patent No. 4,399,00
No. 2 (Fracy Haka), a coated wire electrode is described as being sensitive to many organic cation species in an aqueous sample solution.

The main object of the present invention is to provide a sensing electrode for potentiometric titration that senses charged or capable surfactant molecules in aqueous solutions.

More particularly, the object of the present invention is to prepare titrated time complex compounds having the same 'H1W with anionic, ionic and amphoteric surfactants, and with 10 or more carbon atoms, without prejudice to their composition. It is therefore an object of the present invention to provide a sensing electrode such as can be used for potentiometric titration of alkoxylated JB ionic surfactants produced. Provides IMA thin film electrodes. A coated wire electrode essentially consists of a conductive core member and a semipermeable membrane coated thereon. In a first embodiment, the semipermeable membrane consists of a polymer, a plasticizer, and an ion exchange material consisting essentially of dimidium bromide disulfine blue.

Additionally, the present invention provides a method of manufacturing an indicator electrode for potentiometric titration of surfactants in an aqueous system. Briefly, this method consists of the following steps. forming a conductive metal core; a solvent, a polymeric matrix material;
preparing a solution containing a plasticizer and dimidilam bromide-disulfine blue; and coating a core member with the solution and then drying the coating layer to form a semipermeable ion exchange membrane electrode.

An important advantage of the present invention is that it provides a potentiometric titration system that can reduce the time required for surfactant analysis compared to standard manual titration methods while eliminating exposure of the analyte to organic solvents. It is to provide.

Other objects and advantages of the invention will become apparent from the following description and the drawings which illustrate the preferred embodiments.

Figure 1 shows a potentiometric titration cell using a sensing electrode 11 for sensing anions, cations, nonionic and amphoteric surfactants in solution. There is a sensing electrode inside the cell in Figure 1]
and a standard reference electrode 14, such as a mercury chloride or silver-silver chloride electrode, are placed in a container 3 containing the sample surfactant solution to be titrated. There is. The above-the-surface ends of electrodes 11 and 14 are electrically connected via a conventional electrical device 27, which indicates the voltage between said electrodes, generally as shown in FIG. The device shown is conventional apart from the structure of the electrode 11 shown.

As shown in FIG. 2, the sensing electrode 11 is typically a coated wire electrode and includes a conductive core member 31 having a portion coated with a semipermeable membrane 35 formulated in the manner described below. have In implementation, the core member consists of copper, but silver, carbon, gold, aluminum, platinum and other conductive materials can be used2. Conductive core3.
1, except for the part exposed above the solution, the insulating member 3
Covered with 7. The uncoated portion of the conductive core 31 should be completely coated with the semipermeable membrane 35.

Generally speaking, the base material of the semipermeable membrane 35 is a polymer matrix.
7C) is preferred, but other non-polar, relatively water-insoluble polymeric materials may be used.6 Examples of other polymeric materials are polyvinyl butyryl, polyvinyl bromide, copolymers of polyvinyl alcohol with appropriate comonomers. and those that are insoluble in water and mixtures thereof.

The polymeric substrate is treated with a plasticizer and an appropriate amount of DMB-DSB to form membrane 35, which ultimately becomes an interface within the semipermeable matrix. Polymer is PvC
, the preferred plasticizer is tritol
yl) phosphoric acid esters, but phthalic acid derivatives such as dioctyl phthalate, 2-nitrophenyl alkyl ethers, di-n-alkyl sebacates (seba
Other polar plasticizers may be used, including sebacic acid derivatives such as di-n-alkyl oxalates, and oxalic acid derivatives such as di-n-alkyl oxalates, or mixtures thereof. Another choice of plasticizer depends on the polymeric material used in the membrane, and the plasticizer generally increases the glass transition temperature (T g ) of the polymeric membrane material when added in a plasticizing effective amount to the standard operating temperature ( For example, about 60-90@F = about 15.6-32
．． The material should be such that the temperature can be lowered to below 2°C. The ratio of the amount of polymer to plasticizer (by weight) ranges from at least about 10:1 to 1:10, preferably from about 3:2 to 2:3.

Generalized structural diagrams of DMB and DSB molecules are shown in Figure F.

In this structural formula, M is an alkali metal or an alkaline earth metal, preferably sodium. , X- is a halide or a small anion such as methyl sulfite or tetrafluoroborate.

X- is preferably bromide or iodide. R is hydrogen, methyl, ethyl, propyl or butyl, preferably methyl. R2 and R3 may be the same or different and may be hydrogen, methyl, ethyl, propyl, isopropyl, butyl and isobutyl. R2 and R1
Both are preferably ethyl. In the following, the abbreviation DMB-DSB will be used to refer to the two molecules mentioned above. Thus, it is to be understood that the abbreviation 5 includes the disulfine blue molecule as well as dimidium bromide and cognates. The term dimidium bromide disulfine blue is also used below to specifically denote DMB-DSB in which R1 is methyl, R2 and R3 are ethyl, X- is bromide and Mo is sodium.

The method for forming the sensing electrode 11 is to use a polymer material, a plasticizer,
It also includes providing a liquid mixture of DMB-DSB and a suitable solvent such as THF or cyclohexane. The conductive core 31 is coated with a liquid mixture.

When the mixture dries, it forms a semipermeable, ion-selective membrane that covers and protects the core.

Example of Coating Solution Formulation: According to this example, a coating solution is prepared using a mixture of 0.70 m (l) of tritolyl phosphate ester plasticizer (TTP) in 10 -l of solvent THF. Next, 0.54g of PvC
is added slowly and mixed until the solution is clear. At this time, the solution is based on the assumption that the density of the plasticizer is about 1 gain per milliliter, and the weight of the solvent is ignored.

ing.

Next, 10 grams of the P V C /Plasticizer/THF solution is mixed with 2 grams of the commercially available Dimidium Bromide Disulfine Blue solution, purified and free of about 2.
6X10-'M(7) DMBJ degree and approximately 4.4 X iO
9 Dimidium Blue-Disulfine Blue mixed with having a DSB concentration of 'M' is available from Br1tish Drug Hou, Poole, England.
se Utd. Sourced from. At this point in this example, the solution is dimidium bromide-disulfine.
It can be said that the weight of the blue stock solution is approximately 4 MB-DSB. The rationale for this statement is that a solution of 40% PVC/60% plasticizer (including solvent) 10
grams are mixed with 2 grams of Dimidium Bromide-Disulfine Blue stock solution. The sum of the weight percent of PVC and plasticizer is 100, ignoring the weight of solvent.
It should be noted that %. The ratio of the amount of Dimidium Bromide-Disulfine Blue stock solution to the sum of the weights of polymer and plasticizer plus solvent can range from at least 1:20 to about 1:1 by weight, preferably about 1:1:1. 10 to about 4:10, with about 2:10 being best.

By dry weight, the membrane is approximately 0.138% Dimidium Bromide, 0.043% Disulfine Blue, 44%.

3% TTP and 55.51% PvC.

Further following this example, a gelled component is formed after addition of the dimidium bromide-disulfine blue solution. After long stirring, the gelled and liquid components are filtered through a coarse crucible, and the liquid is separated leaving a purple-colored residue inside the crucible. The residue was transferred to another vial containing 1 ml of solvent l″HF,
Mix until dissolved. The resulting blue-purple viscous solution was used to coat conductive cores 31 as described above. In fact, the dry weight percent of dimidium bromide in the membrane can range from about 0.01% to about 15%, preferably from about 0.05% to about 5%. In reality, the dry weight percent of disulfine blue is approximately 0.
A range of 0.004% to approximately 5% is possible.

Preferably it is about 0.01% to about 2%. Another formulation uses dry DMB and DSB. In this example, solid D
MB and DSB are dissolved in dimethylformamide and the resulting solution is added to the THF/PVC/TTP mixture. Preferably, sufficient solid DMB and DSB is dissolved in dimethylformamide to be present in the membrane from about 0.012 to 7.6% by weight. Additionally, the weight percent of the ion exchange material present in the membrane is between about 0.03 and 1.5.
Preferably 2% DMB plus 0.05 to 2.27% DSB6 and most preferably about 0.15 to 0.05% DSB.
76% by weight of DMB-DSB is present in the film. Thus, for example, a solution of 1.4 tritolyl phosphate ester in 20 mΩ of THF is formed, to which 1.1 g of PVC is added. 0.15
2 g of solid DMB and 0.2270 g of solid DSB are weighed and diluted with DMF in a 50 ml flask. 1ml of DMB-DSB/DMF solution in THF
, /PVC/tritolyl phosphate solution and used to coat electrodes as described above. The above DMB formulation example contains about 0.061% by weight of DMB in the film.
and 0.091% by weight of DSB.

Example of forming a sensing electrode: The sensing electrode was made from 8 gauge copper wire approximately 6 inches long. The wire was insulated with electrical tape except for the bottom half inch. The exposed ends of the wires were polished to shine and then rinsed with acetone. The exposed end of the wire was then dipped three times in the coating solution described above and allowed to dry after each dip. After evaporation of the solvent, the wire was observed to be coated with a shiny blue-purple film. suitably.

This thin film is approximately 100 microns thick. However, functional membranes can be made with thicknesses ranging from about 20 to 1000 microns.

In this example, the composition of the membrane 35 of the sensing electrode 11 of FIG. 2 is about 20% of the stock solution of dimidium bromide-disulfine blue before quenching and drying. The performance of films of this composition versus other compositions can be seen from the information recorded in Tables 1 through 2 below. Data were obtained by potentiometric titration of raw anionic surfactant, raw quaternary ammonium surfactant, and raw amphoteric surfactant, as listed in Table 1. In this table, Adogen
is trimethyl tallow ammonium chloride (ADOGEN 4) manufactured by Shellex Chemical Company.
71), Alfonic refers to sulfated ethoxylated alcohol, sodium salt (AI, FO to IC1412-5) manufactured by Conoco Chemical Company, and LAS
CALSO is a trademark of Pilot Chemical Company.
FT F-90 refers to LAS sodium alkyl sulfonate, SAS is a trademark of American/\\Kist Corporation HO3TAPIJRSAS
60 refers to secondary alkanesulfonate, sodium salt, and BTC refers to Onyx Chemical.
Company's trademark 0nyx BTC50 refers to benzalkonium chloride. Amine oxide is available from Aldrich Chemical Company.
, N-dimethyldodecyl amine oxide. N.E.
ODOL is a product of Shell Chemical Company NEO
Refers to DOL 23-6.5.

Table I: Test surfactant strength M 1'' Adogen 50.5 3
39Alfonic 58.0
435LAS 86.8
342SAS 27.2
-328 BTC 44,9361 Amine Oxide 95.6 229 Table ■ uses electrode 11 of Figure 1 with a film composition of 40% PVC/60% plasticizer with varying levels of Dimidium Bromide-Disulfine Blue. The results of potentiometric titration are shown. In this table, the abbreviation meq/g indicates milligram equivalents of titer per gram of sample. For potentiometric titrations using the coated wire electrode 11 of FIG. 1 with a membrane composition of 50% PVC, 150% plasticizer and various selected levels of dimidium bromide-disulfine blue. The results obtained are shown. Table 1 shows the results of potentiometric titration tests using coated wire electrodes with 60% PVC/40% plasticizer and various levels of dimidium bromide-disulfine blue membrane composition. Potentiometric titrations for each membrane composition were compared with results obtained by two-phase titrations.

Note 1: The weight percent information in Table H calculated from the two-phase titration data also reveals that the best results among the membrane materials were obtained for the two XIDMB-DSB membranes. As far as the tested raw material surfactants are concerned, the data in Table 1 H
The relative deviation of potentiometric versus biphasic titrations for the 0% DMB-DSR membrane is shown to be -1.57% to 0.80%. Comparing the information presented in Tables
C/60% plasticizer 20%DMB-DSB electrodes have a relative deviation percentage of approximately -1,57% to 0.8%
It shows that.

After preparing the titration example, coated wire electrode (40% PVC/60
% plasticizer DMB-DSB) is soaked in an aqueous test solution with an equivalent surfactant of unknown concentration. A silver-silver chloride reference electrode is also immersed in each solution. The surfactants selected for titration are listed in Table 3, and commercially available detergents are included as well as raw surfactants. For comparison, radiant needle A/
Titration was performed on an S RTS 822 automatic titrator and a Fisher Computer-Aided Titrator (CAT) automatic titrator. The titrant is Roh'm Bird Hass Col
HYAMT, a product with the l1pany trademark
NE, and sodium uralyl sulfate (SLS)
Met. The solvent for both titrations was deionized water. SL
S titrant is acid hydrolysed (acid hy-drolys)
is) and the HYM titrant was standardized against it. After each titration, the coated wire electrode was rinsed with deionized water to prevent precipitates from coating the membrane.

For raw surfactants and commercial detergents, Table V reveals that the majority of the two-phase and potentiometric titrations are in good agreement. For raw material surfactants, the average deviation is C
The comparison with the AT automatic titrator is -2.83%, and the comparison with the radiometer automatic titrator is 2.23%. When analyzed using a CAT automatic titrator, the commercially available cleaning agents with a relative deviation of 10% were Oxydol■, 5urf■, and Dynamo.
■, Ga1n■, and Tide■. When analyzed using a radiometer automatic titrator, the commercially available detergents with a relative deviation of 10% were Oxydol■, 5urf■, and Era Pl.
us■, Ga1n■, and Tide■.

Figures 3-5 are graphs obtained by potentiometric titration of anionic, cationic and nonionic surfactants with the electrodes of Figures 1 and 2. Figure 3 shows 0.004M of 0.1 mA titrated with 0.00328M HYAMINE.
This shows the titration curve for SLS of 1.
The end point occurs when 23 mQ of titrant has been added. Figure 5 shows 1+fi 0.004M NEODOL titrated with sodium tetraphenyl borate.
23-6.5 showing the titration curve for 1.36mQ
The end point of the titration occurs when the titrant is added.

It should be noted that the same coated wire electrode is used in each titration.

Another advantage of the coated wire electrode 11 of FIG. 1 is that it can be used for potentiometric titration of raw materials and detergent formulations. The formulation is one that includes surfactant molecules having 10 or more carbon atoms without substantial interference by common inorganic ions or smaller organic molecules. This selectivity of coated wire electrodes will become clear in the discussion below.

Electrode Selectivity Example 8. Experimental samples mimicking a commercial detergent containing 2% phosphorus were made without surfactant. Next, the surfactant
It was added to the sample to achieve a final surfactant concentration ranging from about 8% to about 15% by weight. Prior to mixing with the simulated detergent, the surfactant was potentiometrically titrated to determine the "Expected Value" reported in Table II. The mixture of the simulated detergent with the surfactant was then potentiometrically titrated to give the ``observations'' reported in Table II.

The potentiometric titrations listed in Table 1 utilized oppositely charged titrants. For example, SLS and LSA are 0.004M
Titrated with IIYAMINE 1622R. The raw material amine oxide and the amine oxide detergent solution protonate the amine oxide,
Acidified to pH 1.7 with IM HCQ, then 0.008M sodium tetraphenyl.
Titrated with borate or 0.004M SLS. N.E.
ODOL 23-6.5 was titrated with excess Bac12 (0,2M) to form a cationic complex which was first titrated with sodium tetraphenyl borate.

The information in Table ■ indicates that during the potentiometric titration of a detergent matrix using the coated wire electrode 11 of FIGS.
This shows that there is no substantial interference by inorganic ions. In other words, the relative error from such titrations is within tolerance during the analytical procedure. Furthermore, Table 1 shows nonionic surfactants that cannot be titrated by the conventional two-phase titration method using DMB-DSB as a colorimetric indicator.

It has been shown that titrations can be successfully performed by the potentiometric titration method utilizing the coated wire electrode of FIGS. 1 and 2.

LAS and NEODOL to form a mixed surfactant system for testing the sensitivity of coated electrodes 11
23-6.5 was added into the sample solution containing the induction detergent. Next, an aqueous solution of paris chloride and rum (0.2M) forms a precipitate (barium salt of LAS), so
added to the sample solution. As can be seen from table ■, NE
The expected titration value of ODOL was 2.57 meq/g and the observed value was 2.56±0.04911 Ieq/g. L.A.
When S was titrated with HYAMINE 1622R, the expected value was 1.26 meq/g and the observed value was 1.26 ± 0.
．． It was 038 meq/g.

Other important applications of the coated wire electrode of Figure 1 are in the form of alkoxy groups forming complexes containing polyvalent metal ions such as barium and calcium ions, and non-ionic surfactants containing oxygen molecules. is to perform a potentiometric titration of the agent. Generally speaking, potentiometric titration of such surfactants involves a step in which the surfactant is chelated with an ion, such as a polyvalent metal ion, that places a net charge on the surfactant molecule. Amphoteric surfactants can be charged as well or can be maintained in a pal that makes them ititerated. How to derive such a titration will become clear in the example below.

Example of Potentiometric Titration of Nonionic Surfactants A sample of an alkoxylated nonionic surfactant was digested with water. Barium chloride (BaC1z) was prepared to a concentration of 0.2M with deionized water, and the primary sample added in large quantities to the sample contained 0.008M sodium chloride.
Potentiometric titrations were performed with tetraphenyl borate. For samples containing mixtures of nonionic substances of various molecular weights, the total theoretical milligram equivalents per gram (meq
/g) was calculated from the standard curve and the titration of the product was evaluated against the target value.

Table 1 shows the results of potentiometric titration of alkoxylated non-ionic detergents, in particular ethoxylated non-ionic detergents, according to the method described above. Table 2 shows that potentiometric titration using the coated wire electrode of FIG. 1 is effective in determining the concentration of such surfactants in aqueous solutions. Furthermore, when comparing two-phase titration with HPLC instrument analysis, such potential difference determination of nonionic surfactants is relatively fast and 'cheap'. Other advantages are that the sample volume is minimal and the titration can be carried out in aqueous solution.

As described above, the present invention provides a sensing electrode having a semipermeable membrane containing an ion exchange material DMB-DSB ion pair for measuring alkoxylated nonionic surfactants, anions, cations, and amphoteric surfactants by potential difference. It provides:

The same electrode can be used for potentiometric titration of nonionic surfactants, as well as anionic, cationic and amphoteric surfactants, which when titrated form complex compounds insoluble in water.

Furthermore, the coated wire electrode is excellent for sensing molecules of surfactants containing 10 or more carbon atoms in mixtures containing relatively low molecular weight organic compounds or inorganic ions.

Although the present invention has been described with reference to preferred embodiments, the invention should not be construed as being limited by these embodiments.

For example, although potentiometric titration has been emphasized, the sensing electrode of Figure 1 can be used directly potentiometrically under appropriate circumstances;
Therefore, it can be applied to online potential difference monitoring of surfactant and detergent manufacturing equipment.

Also, although the use of semipermeable membrane materials in coated wire electrodes is emphasized, the materials can be used in any suitable barrel-type electrode. It will be apparent that these and other variations and modifications will readily occur to those skilled in the art from the disclosure. The scope of the claims is intended to cover other modifications and equivalents that come within the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a general schematic diagram of a potentiometric titration cell utilizing an indicator electrode according to the present invention. FIG. 2 is a partially cutaway view of the indicator electrode used in the cell of FIG. FIGS. 3 to 5 are graphs of potentiometric titrations of anions, cations, and amphoteric surfactants using the cells shown in FIG. 1 that utilize pMB-DSB membranes, respectively. [Explanation of main symbols]

Claims (1)

[Claims] 1. A coated wire electrode for potentiometric titration of anionic, cationic, nonionic and amphoteric surfactants in an aqueous medium, comprising: a conductive core member; a semipermeable membrane coating the core member, the semipermeable membrane comprising a polymer, a plasticizer, and essentially DMB-
A coated wire electrode consisting of a semipermeable matrix containing an ion exchange material consisting of DSB and a surfactant in suitable proportions. 2. The coated wire electrode of claim 1, wherein said polymer is selected from the group consisting of polyvinyl chloride, polyvinyl butyryl, polyvinyl bromide, insoluble copolymers of polyvinyl alcohol, and mixtures thereof. 3. The coated wire electrode of claim 1, wherein the plasticizer is a polar material. 4. The plasticizer lowers the glass transition temperature of the membrane to about 60°F.
Claim 3: The substance is a substance that lowers the temperature to below (15.6°C).
coated wire electrodes as described in . 5. The coated wire electrode of claim 1, wherein the DMB-DSB content in the membrane ranges from about 0.014% to about 20% dry weight percent. 6. The coated wire electrode of claim 1, wherein the DMB-DSB content in the membrane ranges from about 0.08% to about 3.79% dry weight. 7. The plasticizer lowers the glass transition temperature of the membrane to about 60°F.
Claim 1: The substance is a substance that lowers the temperature to below (15.6°C).
coated wire electrodes as described in . 8. A thin film for electrodes that is potentiometrically sensitive to anionic, cationic, nonionic, and amphoteric surfactants in aqueous media, comprising a polymer, a plasticizer, and essentially bromide or disulfine blue. A thin film consisting of a matrix containing an ion exchange material consisting of an ion exchange material and a surfactant in a proportion similar to that of a surfactant. 9. The content of the ion exchange material in the thin film is % by dry weight.
8. In a range of about 0.15% to about 0.76%.
Thin film described in. 10.DMB-DS in which the content of the ion exchange material in the thin film is compared to the weight percent of the polymer and plasticizer in the thin film.
Claim 8: The dry weight % of the stock solution B is about 2:10.
Thin film described in. 11. Sensing electrode for use in potentiometric titration of surfactants in aqueous systems, comprising: a) forming a core member of conductive material; b) solvent, semipermeable matrix material, plasticizer; , and DM
A sensing electrode manufactured by: preparing a solution containing B-DSB; and c) coating the core member with the solution and drying the coating layer to form an ion exchange membrane electrode. 12. The sensing electrode of claim 11, wherein the plasticizer is tritolyl phosphate present in a plasticizing effective amount. 13. The DMB is dimidium bromide, and DS
12. The sensing electrode according to claim 11, wherein B is disulfine blue and is present in an appropriate proportion to be detected as a surfactant. 14. The sensing electrode of claim 11, wherein the matrix material is selected from the group consisting of insoluble copolymers of polyvinyl chloride, polyvinyl butyryl, polyvinyl bromide, and polyvinyl alcohol, and mixtures thereof. 15. A method of forming a sensing electrode for potentiometric titration of surfactant molecules of 10 or more carbon atoms in an aqueous system, comprising: a) a solvent, a polymer, a plasticizer, essentially DMB-
preparing a solution containing an ion exchange material consisting of DSB; b) stirring the solution; c) separating a gelled component and a liquid component from the solution; d) dissolving the gelled component in a solvent; e) A method of forming a sensing electrode comprising coating a conductive core member with a dissolved gelling component and drying the coating layer to produce an ion exchange membrane. 16. A method for potentiometric titration of an alkoxylated nonionic surfactant in an aqueous system comprising: a) forming a conductive metal core; b) a solvent, a semipermeable polymeric matrix material, and a plasticizer. and an ion exchange material consisting essentially of DMB-DSB; c) coating the core member with the solution and drying the coating layer to form an ion exchange membrane electrode; d) adding to an aqueous solution containing a nonionic surfactant a cation that forms a complex with the nonionic surfactant; e) the complexed nonionic surfactant within an electrochemical cell containing said ion exchange membrane electrode; A method consisting of potentiometric titration of a solution containing 17. A method for potentiometric titration of a charged surfactant in an aqueous system, comprising: a) forming a conductive metal core member; b) a solvent, a semipermeable polymeric matrix material, a plasticizer, and an essential component. c) coating the core member with the solution and drying the coating layer to form an ion exchange membrane electrode; d) charged surface active material; A method comprising potentiometrically titrating an aqueous solution containing the agent with a titrant having an opposite charge in an electrochemical cell containing said ion exchange membrane electrode.