FI82143C - TEST COMPOSITION FOR CONSTRUCTION OF CONCRETE ELLER DEN SPECIFIKA VIKTEN HOS ETT VATTENHALTIGT PROV. - Google Patents

Description

82143

Test mixture for the determination of the ionic strength or specific gravity of an aqueous test sample - Test composition for the best concentration or specificity of the aqueous test sample

The present invention relates to the determination of the ionic strength or specific gravity of a test sample. More specifically, it relates to a test mixture for determining the ionic strength or specific gravity of an aqueous test sample.

Determining the specific gravity of a liquid has applications in a number of fields. Thus, in far-flung fields of technology such as the brewing industry, urine analysis, water purification, the production of drinking water on a ship at sea, etc., specific gravity measurement is all used. Needless to say, a quick, easy method for determining this property would greatly improve the state of many scientific fields, including all technologies where a rapid, accurate determination of specific gravity would be useful. Thus, for example, if a medical laboratory technician could accurately measure the specific gravity of a urine sample in a matter of seconds, not only would such rapid results assist the physician in his diagnosis, the laboratory's efficiency would be improved to a much greater extent than previously available. possible.

Although the present invention is suitable for use in a wide variety of applications, for clarity, this description is primarily limited to the determination of urine ionic strength or specific gravity. Applications to other fields will become apparent upon understanding how this invention relates to urinalysis.

The determination of urinary specific gravity is of considerable value for the understanding and clinical treatment of electrolytic disorders.

Thus, a complete urinalysis should and usually does include a determination of specific gravity. Generally, such an assay involves the immediate measurement of a specific gravity with a suitable device, but equally useful is the measurement of some relative property, such as osmolality or ionic strength, from which corresponding specific gravity values can then be calculated. Specific gravity is the term dimer and in the case of a solution means the ratio of the weight of a given volume of solution to the weight of an equal volume of water at the same temperature. A solution such as urine has a specific gravity as a function of the number, density, ionic charge and weight of the various substances dissolved in it.

Hydrometers, urinometers, pycnometers, gravimeters and the like are used in previously known methods of determining specific gravity. Although these previously known methods are in most cases satisfactorily sensitive, they all require fragile, space-consuming instruments that must always be cleaned, maintained, and calibrated to ensure their reliability at all times. In addition, there are many disadvantages associated with the operating mechanics of these instruments. There may be difficulty reading the meniscus. Foam or bubbles on the surface of the liquid may interfere with reading. Urinometers tend to stick to the sides of the container that contains the fluid sample. In the case of urine, the amount of sample is often insufficient to accommodate any of the above devices.

The recent breakthrough, which has substantially eliminated all of the above disadvantages and allows a rapid determination of osmolality (and therefore specific gravity), is

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3,824,143 is described in U.S. Patent 4,015,462. This patent discloses the invention of incorporating osmotically brittle microcapsules into a carrier matrix having capsule walls composed of a semipermeable membrane material. Encapsulated inside the walls is a solution that contains some colorant. When the capsules are in contact with a solution with a lower osmolality than inside the capsules, an osmotic gradient is created between the sides of the capsule walls towards the lower osmolality, thus increasing the hydrostatic pressure inside the capsules, causing the capsules to swell and finally break. the content is released. The amount of color caused by this phenomenon is a function of the specific gravity of the solution.

It is clear from the above that in addition to the numerous instruments with which the specific gravity is measured immediately, the specific gravity can also be measured using an indirect means such as the osmolality of the solution. Another way to estimate the specific gravity without measuring it immediately involves an assay that is proportional to the ionic strength of the solution. This means is used in the present invention. It has long been known that the specific gravity of an aqueous system is greatly affected by the presence of charged particles. Thus, in the case of ionized solutions, the specific gravity of the solutions in question can be quite accurately determined by relative measurements of their ionic strength and by comparing the results of these measurements with a pre-calibrated reference system.

The term "ionic strength" means the mathematical relationship between the number of different ionic species in a given solution and their corresponding charges. Thus, the ionic concentration ^ u is represented mathematically by the formula: / U = ci Zd where c is the molar concentration of a given ionic species and Z is the absolute value of its charge. The sum Σ is taken from all the different ionic species in solution.

U.S. Patent No. 4,824,143 discloses the measurement of dissolved sodium or chloride ions. This publication relates to a test device for determining the concentrations of these ions in body sweat. Briefly, the use of ion exchange resins in conjunction with a pH detector is described in this publication. When using this apparatus, the presence of sodium or chloride ions is said to be determined on the basis of the color change of the ion exchange resin caused by the pH detector. Although this publication claims to explain a means of measuring ionic strength, the present inventors have found that the teachings set forth in the examples of said publication cannot be applied to the measurement of specific gravity.

Both the osmolality method and the ion concentration method for determining the specific gravity indirectly could be thought to be affected by the presence of non-ionic particles in terms of their accuracy. Solutions have therefore been proposed to eliminate this potential source of inaccuracy, e.g. a device in which the specific gravity sensitive system contains an ionizing agent capable of converting nonionic solutes to ionized.

The current state of the art, insofar as it relates to the present invention, can be briefly described by saying that many methods, both direct and indirect, for measuring specific gravity are known. Immediate measurement involves the use of fragile, space-sensitive and expensive instruments that must always be cleaned, maintained and calibrated. Of the indirect methods, measuring the colligative property known as the osmolality of a solution is able to give an accurate correlation to the specific gravity. The present invention uses a different aspect, namely the dependence between the specific gravity of the solution and the ionic concentration, and provides an apparatus, mixture and method for exploiting this dependence. U.S. Patent 3,449,080 discloses a method for measuring the concentration of sodium and / or chloride ions in body sweat. This publication takes advantage of the affinity of weakly acidic or weakly basic ion exchange resins for unknown ions and the color exchange ability of known pH indicators.

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Briefly, the present invention relates to a test mixture, an apparatus, and a method for determining the specific gravity of an aqueous test sample. The test mixture comprises a weakly acidic or weakly basic polyelectrolyte polymer that is at least partially neutralized and an indicator substance capable of forming a detectable response due to ion exchange between the polyelectrolyte and the test sample. The device according to the invention comprises a carrier matrix in which said mixture is incorporated. The method according to the invention comprises contacting the test sample with the device or mixture and taking into account a detectable response such as a color change.

Figures 1-8 are graphical representations of (a) the responses of three polyelectrolyte to test samples of varying specific weights, and (b) the titration, i.e., partial neutralization, of these polymers. Thus, Figures 1, 2 and 3 show titration curves of a copolymer of methyl vinyl ether and maleic anhydride, polyacrylic acid and polyvinylamine, respectively. Figures 4, 5 and 6 show the behavior of these polyelectrolytes in determining the specific gravity of urine after varying degrees of partial neutralization of the polymer-dependent group. Figure 7 shows the similar behavior of polyvinylamine in aqueous saline solutions of different concentrations. Figure 8 finally shows the behavior of the primary device.

The composition according to the invention contains, as one component, a weakly acidic or weakly basic polyelectrolyte. Numerous examples of such polymers are found in the prior art, and their common features are centered around the degree of dissociation of ionic dependent groups when the polymer is exposed to an aqueous environment. Most polyelectrolytes are soluble or partially soluble in water, and readily ionizable, depending on the ionic nature of (a) the aqueous system and (b) the ionizable groups on the polymer chain.

Thus, the polyelectrolyte is weakly or strongly labeled as acidic or basic depending on its ionic behavior. In general, a polyelectrolyte which, when in contact with water, ionizes almost completely, such as polyvinyl sulfuric acid and polystyrenesulfonic acid, is considered to be a strong polyelectrolyte. On the other hand, weak polyelectrolytes contain weakly acidic or basic ionizable groups. The molecular chain of these polymers along the charge density can be varied by varying the degree of neutralization. Examples of weakly acidic or weakly basic polyelectrolytes which are particularly suitable for use in the present invention include polyacrylic acid, polymaleic acid, a copolymer of maleic acid and methyl vinyl ether, polymethacrylic acid, a copolymer of styrene and maleic acid (4), a copolymer of styrene and maleic acid.

The composition of the present invention contains weakly basic and weakly acidic polyelectrolytes, but in particular contains those which are partially neutralized. At least some of the functional groups of the polymer, whether weakly acidic (e.g., COOK) or weakly basic, are first partially titrated with a base or acid, respectively, before the polyelectrolyte is included in the test mixture. Typically, aqueous solutions of the titrant are used, and basic titrants include solutions known to reasonably skilled chemists for NaOH, KOH, Na 2 O 2, polyethyleneimine, tris (hydroxymethylamine) methane, and the like. Surprisingly, such partial titration, i.e. neutralization, has been found necessary to allow the detection of significant differences in the specific gravity levels of the test solutions.

Preferably, the polymer is neutralized by at least 50%, i. at least about half of the ionizable groups are neutralized. The ideal neutralization range, which has also proven to be preferred for use in the present invention, is about 75% to about 95% neutralization, of which 90% has been found to be most suitable to provide the greatest difference in pH change or other detectable response to specific gravity or ionic strength.

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The polyelectrolyte selected for use in the present invention must, as mentioned above, be partially neutralized. This is accomplished by titrating the polymer with a suitable acid or base if desired, or by any other means that achieves the desired result, namely, partial neutralization. Thus, Figure 1 shows a titration curve of a copolymer of maleic anhydride and methyl vinyl ether marketed by Gantre® S-97, General Aniline and Film Corporation, with sodium hydroxide in aqueous solution. Figure 2 shows the same data for polyacrylic acid and Figure 3 for polyvinylamine.

The second element of the mixture is an ion exchange-sensitive indicator substance. It may take a variety of forms, such as a pH meter, a pH indicator, or other means by which a person of ordinary skill in the art can perform the assay. Thus, a pH meter can be used with a constant pH electrode (in solution systems) or a surface pH electrode (when the mixture is incorporated into a carrier matrix). The indication of the pH meter can then be detected at different ionic strength values and then a reference system constructed in which a certain change in pH corresponds to a certain ionic concentration in the test sample.

Alternatively, known pH-sensitive, color-forming reagent mixtures can be used and these can cause a color change or color appearance that can be detected by the person performing the measurement and that indicates the ionic strength or specific gravity of the system under test. If a color-forming agent is used, a reference color system can be constructed in advance so that a rapid visual comparison of the mixture and the reference system gives the desired results. Examples of suitable coloring agents for use in the present invention include bromotymolysin, alizarin, bromocresol purple, phenol red and neutral red; of which bromotymolini has been found to be particularly suitable.

The present invention also relates to an apparatus in which the aforementioned test mixture is incorporated into a carrier matrix so as to provide a tool for obtaining rapid, reliable estimates of the specific gravity of solutions. The carrier matrix is usually, but not necessarily, some porous material such as filter paper. Other forms of base matrix known in the art include felt, porous ceramic strips, and woven or felted glass fibers (U.S. Patent 3,846,247). Wood, fabric, sponge, and clay-containing materials can also be used (U.S. Patent 3,552,928). All of these carrier matrix materials can be used in the present invention, and so can others. It has been found that filter paper is particularly suitable.

In a preferred embodiment, the filter paper is soaked in partially neutralized polyelectrolyte dissolved or suspended in water or another suitable carrier that is readily determined by normal laboratory experiments, and then dried. The polyelectrolyte-containing filter paper is then soaked in a methanolic solution of the desired indicator (such as bromothymol) or in a suitable solvent such as ethanol, N, N-dimethylformamide or dimethyl sulfoxide, and then dried. Alternatively, a single dip method can be used in which the polyelectrolyte and the indicator are included in the stock solution or suspension at the same time.

The dried reagent-containing carrier matrix can be attached to a background material, if desired. Thus, the test apparatus in its preferred embodiment comprises a filter paper backing matrix incorporating a partially neutralized polyelectrolyte and an indicator as described above, which matrix is attached to one side of an elongate body of transparent polystyrene film. The matrix is attached to one end of the film by any suitable means, such as double-sided adhesive tape (Double Stick, available from 3 M-Company), with the other end of the polystyrene film acting as a handle. During use, the device is held from the free end of the polystyrene film backing material and the matrix is immersed in a test sample (e.g., urine) and quickly removed. Any color formation or other detectable response is detected after a predetermined time and compared to a reference standard corresponding to known responses of ionic concentrations or specific gravities of the solution.

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The reference standard used in each case depends on whether the mixture is used alone or incorporated into carrier matrices, as well as on the particular means of indication. Thus, if the partially neutralized polyelectrolyte is added directly to the test sample and the indication is a pH meter, a reference standard can be formed by adding a standard weight amount of polyelectrolyte to a standard volume of a solution of known ionic strength. The change in pH before and after the addition of the polyelectrolyte is recorded using a pH meter. This procedure is followed with a series of solutions of varying, known ionic strength. The same procedure is used to determine the ionic strength of an unknown test sample, and the change in pH is compared with changes in the pH of known solutions.

When a test device is used which has a carrier matrix containing a partially neutralized polyelectrolyte and a color former, the reference standard may comprise a series of color blocks representing the color developed by the carrier matrix after a predetermined time by solutions of known ionic strength. When testing an unknown sample, the carrier matrix of the test device is embedded in the sample, removed, and the appearance or change of color after said predetermined time is detected. The resulting color response is then compared to the color blocks of the reference standard to determine the ionic strength or specific gravity of the sample.

The following examples are presented to further illustrate the use of the present invention. Accordingly, preferred embodiments of the invention will be explained and analyzed. The examples are intended to be illustrative only and in no way to limit the scope of the invention described above and defined in the claims.

Example 1 - Partial Neutralization of a Copolymer of Maleic Anhydride and Methyl Vinyl Ether This experiment was performed to investigate the partial neutralization of a polyelectrolyte (Gantre®-S-97 marketed by General Aniline and Film Corporation) and its effect on the specific gravity of the solution.

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A modular automatic titrator was assembled to titrate various polyelectrolytes for research in connection with the present invention. The titration device consisted of an automatic pipetting device, Model No. 25000, supplied by Mikromedic Systems, Inc. This experiment is capable of dispensing a constant volume of titrant per unit time into the polymer solution to be titrated. The titrant addition flow (i.e., the rate of neutralization of the polyelectrolyte) was adjusted by selecting the pipette volume, the dispensed portion of the pipette volume, and the titrant concentration. A change in pH during titration was detected using a standard pH electrode and an Orion Model 701 digital pH meter. The output of the pH meter was fed to a Hewlett-Packard Model 17500A 25 cm strip plotter, the scale of which was calibrated so that 2.5 cm corresponded to a change in one pH unit. Thus, the plotter provided continuous monitoring of pH changes over time (and thus relative to the volume of titrant added).

This apparatus was used to titrate Gantrez S-97, a weakly acidic polyelectrolyte, and to account for its partial neutralization. A Gantrez solution containing 20 g of this polyelectrolyte per liter of deionized water was prepared. Three 100 ml aliquots of this solution were placed in 250 ml beakers. One aliquot was made 0.1 normal and the other 1.0 normal with NaCl. No salt was added to the third aliquot. By titrating each of these polyelectrolyte solutions with 1.0 N NaOH in a 50 mm pipette at a flow rate of 9.0 ml of titrant per hour and plotting the pH change per volume of titrant, it was possible to study Gantrez titration properties and the effects of partial neutralization on its ability to separate varying ionic strengths.

The titration data obtained in this experiment are shown graphically in Figure 1. Curve A represents the titration of the polyelectrolyte solution to which no salt has been added, curve B represents the titration of the polyelectrolyte solution made normal to 0.1% NaCl and curve C represents the titration of its polyelectrolyte solution, containing NaCl 1.0-normally. The clear separation between curves A, B and C in Figure 1 shows the effect of ionic strength on the polymer

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11 82143 to the apparent pK. Thus, taking into account the degrees of separation between the titration curves, i. Differences in pH values for a given amount of titrant can be estimated by maximization relative to the determination of different specific gravity levels. For example, greater segregation is observed in the range between pH 5 and pH 10 than in other stages of polymer neutralization. The curves in Figure 1 show that optimum separation occurs when the degree of neutralization of the polymer is from about 70% to 95% or more (i.e., after the addition of about 6.0-9.0 ml of titrant). Not only is this information useful in evaluating the effectiveness of the polymer in aqueous systems, it also helps to determine the optimum neutralization of the polyelectrolyte to be incorporated into the parent matrix, as seen in Example IV below.

The percentage neutralization of a particular polyelectrolyte can be calculated from the titration data as shown graphically in Figure 1 by curve A (titration of the polyelectrolyte, here Gantrez S-97 without addition of salt). The percentage degree of neutralization of the polymer is calculated for a given titrated pH of the polymer solution by finding this pH of the solution on the vertical axis, drawing a horizontal line from the vertical axis to curve A and drawing a vertical line from this point on curve A to the horizontal axis (i.e. 1.0 ml NaOH). The volume of titrant (corresponding to the point of intersection of the vertical line and the horizontal axis) divided by the volume of titrant at the end point of the titration and multiplied by 100 gives an accurate approximation of the percentage of neutralization of the polyelectrolyte. The end point of the titration is indicated by the vertical to the right of curve A, and can be expressed as the volume of titrant added.

Thus, for Gantrez S-97, the endpoint of Figure 1 is very close to 9.0 (about 8.6) ml of 1.0 N NaOH titrant. Titration of the Gantrez solution in deionized water to a pH of about 7.5 corresponds to about 6.0 ml of titrant. Since the end point is about 8.6 ml of titrant, the% neutralization can be calculated as follows: 6.0 ml (titrant) η _, Λ / α - -i'— x 100 = 70 (% neutra- 8.6 ml (titr. substance at endpoint) found) i2 821 43

Example II - Partial Neutralization of Polyacrylic Acid This example was performed to investigate the partial neutralization of polyacrylic acid and the effect of this neutralization on the utility of this polyelectrolyte in determining the specific gravity of the solution. The automatic module titrator, pH meter and electrode were the same as described in Example I, as was the procedure.

A solution of polyacrylic acid, a weakly acidic polyelectrolyte obtained from Aldrich Chemical Co. (Catalog No. 19 205-8), was prepared by dissolving 20 g of polymer in one liter of deionized water. Three 100 ml aliquots of this solution were placed in 250 ml beakers. One of the aliquots was made to 0.1-n and the other to 1.0-n relative to NaCl. No salt was added to the third aliquot. Each of these solutions was then titrated with 10.0 NaOH using a 50 mL pipette at a flow rate of 3.0 mL of titrant per hour. The results are shown in Figure 2, where curve A represents the unsalted polyelectrolyte, curve B represents a 0.1 n solution relative to NaCl and curve C represents a 1.0 n solution relative to NaCl.

The results shown in Figure 2 show that the greatest difference in ionic strength (i.e., between curves A, B, and C) occurred from about 50% to about 95% or greater polymer neutralization (i.e., from about 1.5 to about 3%). .0 ml of titrant). Thus, for example, after titration of the polymer for a period of 40 minutes (2.0 ml with 10 N NaOH), a significant difference in the pH obtained can be seen depending on the ionic concentration of the solution. Curve C, corresponding to 1.0 N NaCl, gives a pH value of about 5.25, curve B, corresponding to 0.1 n NaCl, gives a pH of about 5.8, and curve A, corresponding to 0 NaCl concentration. , gives a pH of about 6.25. Thus, the ionic concentration or specific gravity of a particular solution can be approximated by using these values and interpolating between them.

Example III - Partial Neutralization of Polyvinylamine This experiment was performed to investigate the partial neutralization of a weakly basic polyelectrolyte, namely polyvinylamine obtained from Dynapol Inc., and the effect of this neutralization on the determination of specific gravity.

The automatic module titration apparatus, pH meter and electrode described in Example 1 were used, and the same procedure was used.

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A solution of polyvinylamine was prepared in the form of its hydrochloride salt (fully neutralized) having a molecular weight of about 60,000 to give a polymer content of 20.0 g of deionized water per liter. Three 100 ml aliquots of this solution were placed in 250 ml beakers. One of the aliquots was made 0.5 normal and the other 3.0 n-NaCl. No salt was added to the third aliquot. Each of these solutions was then titrated with 1.0 N NaOH, using a 50 mL pipette, with a flow rate of 9.0 mL of titrant per hour. The results are shown in Figure 3, where curve A represents the titration of the polyelectrolyte solution to which no salt has been added, curve B represents the titration of the solution made to 0.5 n with NaCl and curve C represents the titration of the solution made with 3, To 0-n relative to NaCl.

The data shown in Figure 3 show that very little Respons in relation to ionic strength is present when the polymer is in a completely amine or neutralized form (pH 10, 35 min), while excellent separation occurs at lower degrees of titration, i. with a broader neutralization of the polymer. Thus, the ability of polyvinylamine to distinguish between different ionic strength levels and inversely varies with the amount of titrant, so that excellent separation is obtained at the beginning of the titration (neutralization over 95%), whereas in O-neutralization (when about 5.3 ml of titrant is added) the separation is not occurs at all.

Example IV - Behavior of Copolymer of Maleic Anhydride and Methyl Vinyl Ether in the Carrier Matrix The solution used in Example I (20 g of Gantrez S-97 per liter of deionized water) was further studied to account for its behavior in measuring the specific gravity of the stream when included in the carrier matrix.

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A test device sensitive to ionic strength or specific gravity was prepared by incorporating the Gantrez S-97 solution into the filter paper and then drying. Several of these test devices were fabricated to study the behavior of polyelectrolyte at different degrees of neutralization. Thus, aliquots of Gantrez S-97 solution were neutralized to varying degrees by titration with NaOH.

Filter paper strips (No. 204) from Eaton and Dikeman were immersed in these partially titrated aliquots, respectively, and then dried. Saturated, dried strips from each aliquot were then immersed in urine of known high specific gravity and deionized water, and their pH was measured. A pH meter equipped with a planar electrode obtained from Markson Science Inc. (No. 1207 Bacti-Media composite pH reference electrode) was used for these measurements. ΔρΗ: η, so. the pH difference values of completely similar strips immersed in deionized water and urine of known specific gravity, respectively, are shown in the following table.

Polyelectrolyte solution - ΔρΗ values developed by the pHs of urine aliquots of different specific gravity

S.g. S.g. S.g.

1.030 1.015 1.005 4.75 0.20 0.29 0.32 6.0 1.04 0.91 0.54 7.0 1.70 1.44 0.65 8.0 2.41 2.06 1.04 9.25 3.24 2 , 29 1.09 9.75 3.52 2.66 1.65

The figures in the table above are plotted in Figure 4, which shows three curves representing the ΔρΗ values generated by table-specific urine when tested on strips made from aliquots of different degrees of neutralization. It can be seen from Figure 4 that the degree of separation of the curves increases considerably with the degree of neutralization of the polyelectrolyte, i. as its pH increases. Thus, the more neutralized the Gantrez polyelectrolyte, the greater its ability to distinguish urine specific gravity levels.

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Example V - Behavior of polyacrylic acid in carrier rice

The polyelectrolyte used in Example II (20 g of polyacrylic acid per liter of deionized water) was further studied to account for its behavior in measuring the specific gravity of urine when incorporated into a carrier matrix.

Test equipment was prepared and tested as in Example IV, except that Gantrez S-97 was replaced with polyacrylic meat. A solution of 20 g of polyacrylic acid per liter of deionized water was prepared. Aliquots of this solution were titrated with 10 N NaOH until the pH levels listed in the following table were reached. Strips of filter paper obtained from Eaton and Dikeman (No. 204) were immersed in these aliquots, respectively, and dried. They were each immersed in urine of different known specific weights and deionized water, and their pH was measured. The pH values were determined as in Example IV and are shown in the following table. A pH meter with a planar electrode obtained from Markson Science Inc (No. 1207 BactiMedia composite pH reference electrode) was used for the measurements.

ΔρΗ values developed by pH salts of polyelectrolyte solutions with different specific gravity flow quotas

S.g. S.g. S.g.

1.005 1.015 1.030 4.0 0.11 0.05 0.00 5.0 0.5 0.64 0.70 6.0 0.56 0.88 1.09 7.0 0.76 1.29 1.68 7.5 0.91 1 .40 1.98 8.0 1.15 1.73 2.29 8.25 1.10 1.82 2.10

From the figures in the table above, graphs are drawn in Fig. 5, which, like Fig. 4, shows that the degree of separation of the curves therein increases considerably with the degree of neutralization of the polyelectrolyte, i. as its pH increases.

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Example VI - Behavior of polyvinylamine in a carrier matrix

The polyelectrolyte used in Example III was further studied to account for its behavior in measuring varying urinary specific weights when incorporated into a strain.

Test equipment was prepared and tested as in Examples IV and V, except that polyvinylamine was used instead of Gantrez S-97 and polyacrylic acid, respectively. A solution was prepared containing 20 g of polyvinylamine (obtained from Dynapol Inc sufficient, molecular weight 60,000, see Dawson et al., J.A.C.S. 98, 5996, 1978) per liter of deionized water. The polyelectrolyte used was in the form of the hydrochloride and thus in a completely neutralized state. Aliquots of this solution were each titrated with 1.0 N NaOH until the pH levels of the solutions shown in the following table were reached. Strips of filter paper obtained from Eaton and Dikeman (No. 204) were immersed in each of these aliquots and dried. They were each immersed in urine samples of different known specific weights and deionized water, and their pH was measured using the planar electrode described in Examples IV and V. The values of ÄpHr were then determined as in Examples IV and V and are shown in the following table.

Aliquots of pH of polyelectrolyte solutions developed by urines of different specific weights

S.g. S.g. S.g.

1.005 1.015 1.030 2.8 1.05 1.60 1.78 3.0 1.06 1.64 1.92 3.5 0.89 1.11 1.29 4.0 0.89 1.17 1.21 6.0 +0 .06 -0.10 -0.33 8.0 -0.71 -0.99 -1.70 10.0 -1.45 -1.47 -2.24 11.0 -1.80 -2.50 -2.81 12.0 -2.24 -2.57 -3.07

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17 821 43 The curve showing these figures, Figure 6, shows a useful separation when the polyelectrolyte is partially neutralized below about pH 5. Thus, a urine sample with a specific gravity of 1.005 shows a much smaller change in pH than a urine sample with a specific gravity of 1.030. A urine sample with a specific gravity of 1.015 gave ΔρΗ: η values between, as expected.

This effect is even more dramatic when polyvinylamine testing devices are immersed in aqueous salt solutions and deionized water of different ionic strengths, respectively, and their pH values are measured to obtain ΔρΗ: η values. The strips prepared as above were tested with different concentrations of sodium chloride in deionized water. In terms of individuals, these saline concentrations were 0.5, 1.5, and 3.0 normal to NaCl. The results obtained in this experiment are shown in the following table and as curves in Figure 7. Curves A, B and C correspond to 3.0-n, 1.5-n and O, respectively.

0.5 N NaCl solution.

Polyelectrolyte solutions pH ΔρΗ values of 0.5% n NaCl 1.5 -N NaCl 3.0 -N NaCl 2.8 0.60 0.63 0.93 3.0 1.04 1.37 1.46 3.5 0.88 0.99 1.23 4.0 1.00 1.32 1.61 6.0 0.90 0.93 1.03 8.0 0.64 0.64 0.68 10.0 0.61 0.64 0 .60 11.0 "0.01 -0.03 -0.10 12.0 -0.09 -0.22 -0.29

As shown in Figure 7, at pH 10, where the polyelectrolyte is substantially proton-free and uncharged, the variation in salinity has substantially no effect. However, partial neutralization of the polymer results in a steadily increasing behavior of divergence in response to ionic concentration, as evidenced by the increasing separation of the relevant curves, reflecting the broadly divergent ΔρΗ response to different high ionic concentrations.

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Example VII - Test apparatus made using maleic anhydride / methyl vinyl ether copolymer and bromothymol blue The test mixture of Example I was used in a carrier matrix together with bromothymol blue, a known pH indicator, to examine the properties of the present invention for visual determination of specific gravity.

A solution was prepared containing 20 g of Gantrez-S-97 per liter of deionized water. An aliquot of this solution was titrated with NaOH until the pH of the resulting solution was 8.0 as measured by the pH meter and electrode described in Example I. A strip of filter paper (Eaton & Dykeman No 204) was immersed in a partially titrated (neutralized) aliquot and then dried. The dried polymer-containing strip was then immersed in a 1.2 g / l solution of bromothymol blue in methanol. After drying, the filter paper strip was attached to a clear, plastic backing (Trycite, obtained from Dawson Chemical Cor) using a double-sided adhesive tape (Double Stick, obtained from 3M Company). The test devices thus obtained each comprised a Trycite strip measuring about 9 x 0.5 cm, one end of which supported a saturated square of filter paper measuring 0.5 x 0.5 cm. The rest of Trycite served as a handle.

The sensitivity of these test devices to specific gravity was examined by testing them with three urine samples of different specific gravity and with water. The device was immersed in the respective test solution and quickly removed. After 60 seconds the device was studied reflection photometer to examine and measure the test device of the reflected light intensity in the visible region of the spectrum which is half seconds.

The results obtained at 60 seconds are plotted in Figure 8, which shows a clear separation that allows the specific gravity to be easily and accurately separated between water (om. Weight 1,000) and urine samples with specific gravity levels of 1.005, 1.015 and 1.030. Visual color separation was equally easy, with the device displaying blue with water, blue-green with a urine sample

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i9 821 43 had a specific gravity of 1.005, green with a specific gravity of 1.015 and yellow with a specific gravity of a urine sample of 1.030.

This example shows the relationship between the partial neutralization of a polyelectrolyte and the determination of specific gravity or ionic strength. The pH of the Gantrez solution from which the device was made was about 8. As can be seen from curve A in Figure 1, this pH corresponds to a consumption of about 6.8 ml of titrant. Using the calculation method described in Example I, this corresponds to about 79% neutralization. The considerable difference between the specific gravity levels achieved in the experiment described above must be attributed to this relatively high degree of neutralization of the polyelectrolyte.

Claims (8)

A test composition for determining the ionic strength or specific gravity of an aqueous sample, characterized in that it comprises a weakly acidic or slightly basic polyelectrolyte polymer neutralized to at least 50%, and a pH indicator substance which provides a visible response to ion exchange. between the polyelectrolyte and said sample. Composition according to claim 1, characterized in that said polyelectrolyte is polyacrylic acid. Composition according to claim 1, characterized in that said polyelectrolyte is a copolymer of maleic acid and vinyl methyl ether. Composition according to claim 1, characterized in that said polyelectrolyte is polyvinylamine. Composition according to claim 1, characterized in that said polymer is a weakly acidic polyelectrolyte. Composition according to claim 1, characterized in that said polymer is a weakly basic polyelectrolyte. 7. Composition according to any of claims 1-6, characterized in that said polyelectrolyte polymer is neutralized to 75 - 95%. Composition according to claim 1, characterized in that said polyelectrolyte is methyl vinyl ether / maleic acid copolymer and said indicator is bromothymol bare.