LU81861A1 - COMPOSITION, TEST DEVICE AND METHOD FOR DETERMINING THE ION CONCENTRATION OR THE SPECIFIC WEIGHT OF A LIQUID SAMPLE - Google Patents

Description

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The present invention relates to the determination of the ion concentration or the specific weight of a test sample. More particularly, the invention relates to a composition, a test device and a method for determining the ionic concentration or the specific weight of an aqueous test sample.

The determination of the specific weight of a liquid is applied in many techniques. This is how unrelated disciplines such as brewing, urinalysis, water purification, preparation of drinking water aboard a ship at sea, etc. all involve the measurement of specific weight. It goes without saying that an easy and rapid method for the determination of this property would constitute a huge advance in many scientific techniques, including technologies where a rapid and precise determination of the specific weight would be beneficial. For example, if a technician in a medical laboratory could accurately measure the specific gravity of a urine sample in seconds, not only would the results obtained quickly help the doctor in his diagnosis, but the laboratory performance would also increase to such a degree that many more analyzes could be performed than before.

Although the present invention lends itself to a wide range of applications, for reasons of clarity, the present description will be given largely in terms of determining the ionic concentration or the specific weight of urine. Applications to other disciplines will emerge on their own if we understand how

Determining the specific gravity of urine is of considerable importance in understanding and? clinical treatment of electrolyte disturbances. From | therefore, a complete urinalysis must (and usually |) include a determination of the specific weight.

| As a general rule, this determination involves direct measurement of the specific gravity with an appropriate device, but it is also useful to measure certain other related properties such as osmolality or ionic concentration, these properties then being able to be again related to the corresponding values relating to the specific weight.

Test weight is a term without dimension

Ision and, in the case of a solution, it is the ratio between the weight of a certain volume of this solution and that of an equal volume of water at the same temperature. For solutioi! such as urine, the specific gravity is a function of the number of the density, the ionic charge and the weight of the various | dissolved solute species.

i j In the prior art methods for determining the specific gravity, | hydrometers, urinometers, pyenometers, gravity. meters and the like. Although these prior art methods have, in most cases, a satisfactory sensitivity, they all involve fragile and bulky instruments which must be constantly cleaned, maintained and calibrated in order to continuously preserve their reliability. In addition, many disadvantages are ace? ciés mechanical systems involved in the use of these instruments. Reading the meniscus can be difficult. The foam or bubbles that form - relate to urinometers, they tend to adhere to the walls of the container containing the liquid sample. In the case of urine, the amount of sample is frequently inadequate for either of the above devices.

Recently, a path has been opened by which practically all the above-mentioned drawbacks are eliminated, while ensuring rapid determination of the osmolality (and therefore of the specific weight); this method is described in the patent of the United States of America No. 4,015,462 applied for on January 8, 1976 in the name of the Applicant.

1 In this patent, an invention is described according to which is incorporated, into a support matrix, osmotic microcapsules-ment fragile and whose walls consist of a semi-permeable membrane. Inside these walls is a solution containing a coloring substance. When the capsules come into contact with a solution having an osmolality lower than that of the solution contained in the capsules, there occurs, through the walls of the latter, an osmotic gradient towards the lower osmolality, raising the pressure hydrostatic inside the capsules, so that the latter swell and eventually break, releasing their colored content. The degree of coloration resulting from this phenomenon depends on the specific weight of the solution.

* From the above discussion, we can see. that in addition to the numerous devices making it possible to directly measure the specific gravity, one can also measure the latter using an indirect means such as the osmolality of a solution. Yet another method for evaluating the specific nid without measuring it directly is an ionic solution of a solution. According to the present invention, one; uses this method. It is well known that the specific gravity of an aqueous system is strongly influenced by! the presence of charged species. This is how, in the

J

In the case of ionic solutions, we can give a narrow approximation of the specific weight of the respective solutions by means of measurements proportional to their ionic concentrations and by relating these measurements to a reference system; i; ·; precalibrated rence.

| * h The expression "ion concentration" designates i the mathematical relationship between the number of different types ij of ionic species in a particular solution and their respective charges. This is how the ionic concentration ü that p is mathematically represented by the following formula: 1 Σ 2 *. 2 i i i; in which c indicates the molar concentration of a particular ionic species and z indicates the absolute value of its charge. The sum £ indicates all of the different; types of ions in solution.

In US Patent No. 3,449,080, the measurement of dissolved sodium or chloride ions is described. This reference relates to a test device for determining the concentrations of these ions in the »| body sweating. In summary, this patent describes the use of ion exchange resins with a pH indicator. When using this device, the presence of sodium or chloride ions is determined by a change in color in the ion exchange resin under the effect of the nH indicator. Then aue this reference - 6 - ion centration, the Applicant has found that this technique, as described in the examples, is inapplicable to the measurement of the specific weight.

As can be imagined, as far as precision is concerned, the methods in which osmolality and ion concentration are used to indirectly determine the specific gravity could be altered by the presence of non-species. ionic. Consequently, United States patent application No. 716,962 filed August 23, 1976 relates to a method for eliminating this virtual source of inaccuracy and describes therein a device in which the specific system sensitive to specific gravity contains an ionizing agent capable of transforming the nonionic solute into an ionized species.

In order to summarize the current state of the art insofar as it relates to the present invention, numerous methods are known for measuring the specific gravity, both directly and indirectly. Direct measurement involves the use of devices which are fragile, bulky and expensive and which, moreover, require constant cleaning, maintenance and calibration. Among the indirect processes, the measurement of the properties of a solution which are linked together and which are known as "osmolality", can provide a precise correlation with the specific gravity. The present invention uses a different perspective, namely the relationship between the specific gravity and the ion concentration of a solution, and it provides a device, a composition and a method making it possible to take advantage of this relationship. In the patent of the United States of America n ° η / concentration of sodium ions and / or chloride in the perspiration of the body. According to this reference, one uses the affinity of weakly acidic or weakly basic ion exchange resins with respect to unknown ions, as well as the modifying power of coloring of indicators of π,! j pH known. To the knowledge of the Applicant, there is currently no technique describing or suggesting the subject of the present invention.

In summary, the present invention relates to! test composition, device and method for; = determine the specific weight of an aqueous sample.

This composition consists of a weakly acidic or weakly basic polyelec trolyte-forming polymer which has been at least partially neutralized, as well as an indicator substance I capable of producing a detectable response to a | ion exchange between the polyelectrolyte and the sample.

The device of the present invention consists of a! support matrix incorporated into this composition. The method ij of the present invention consists in putting a sample | test in contact with this device or composition, j I then observe a detectable response such as a change j; of coloring.

In the appended drawings: FIGS. 1 to B are graphical representations * (a) of the responses of three polyelectrolytes to test samples having variable specific weights i · Îand (b) of the titration or partial neutralization of these polymers. This is how Figures 1, 2 and 3 show ί titration curves for a methvl- ether copolymer! Vinyl and maleic anhydride, polyacrylic acid and - 8 - indicate the yields of these polyelectrolytes in determining the specific gravity of the urine after partial neutralization, to varying degrees, of the branched polymeric group. Figure 7 shows a similar yield of polyvinylamine in aqueous saline solutions with varying concentrations. Finally, Figure 8 shows the performance of a preferred device.

An ingredient of the composition of the present invention is a weakly acidic or weakly basic polyelectrolyte. Numerous examples of polymers of this type are known in the art, their common characteristics being centered on the degree of dissociation of the branched ionic groups when the polymer is subjected to the influence of an aqueous ambient medium. Most polyelectrolytes are soluble or partially soluble in water and they are easily ionizable depending on the ionic nature (a) of the aqueous system and (b) of the ionizable species present on the polymer chain.

This is how a polyelectrolyte is said to be weakly or strongly acidic or basic depending on its ionic behavior. As a general rule, a strong polyelectrolyte is a polyelectrolyte which ionizes almost completely on contact with water, for example, polyvinylsulfuric acid and polystyrene-sulfonic acid.

On the other hand, weak polyelectrolytes contain weakly acidic or basic ionizable groups. The charge density can be varied along the molecular chain of these polymers by varying the degree of neutralization. Among the weakly acidic or weakly basic polyelectrolytes which are particularly applicable - acrylic, polymaleic acid, the acid copolymer t | maleic and methyl vinyl ether, polymethacrylic acid, l, the copolymer of styrene and maleic acid, poly (4-vinylpyridine) and others.

| The composition of the present invention includes weakly basic and weakly acidic polyelectrolytes, but more particularly polyelectrolytes which have been partially neutralized. At least some groups !! functional, let them be weakly acidic! (for example, COOH) or weakly basic, are first partially titrated with a base or an acid respectively before incorporating the polyelectrolyte into the composition | of test. More specifically, aqueous solutions of a titration product are used and, among basic titration products, there are solutions of NaOH, KOH, N ^ CO ^, polyethyleneimine, tris- (hydroxymethylamino ) -methane and other products known to chemists specializing in this technique. Surprisingly, we found that! this neutralization or partial titration was necessary; in order to be able to establish a significant differentiation j between the values relating to the specific weight of the solution: test.

Preferably, the polymer is neutralized to at least about 50%, that is to say that at least about half of the ionizable groups are neutralized. An interval! »Ideal of neutralization which proved to be by far preferred for • i | the present invention is between about 75 and about | 95% '; thus it was found that neutralization ï at 90% constituted an optimal value for obtaining a maximum separation in the change of pH or another ionic response.

As indicated above, the polyelec trolyte used according to the present invention must be partially neutralized. For this purpose, the polymer is titrated with a desired base or appropriate acid or by any other means ensuring the desired partial neutralization. Thus, Figure 1 gives the titration curve of "Gantrez S-97" (registered trademark for a copolymer of maleic anhydride and methyl vinyl ether sold by "General Aniline and Film Corporation") with 1 ' sodium hydroxide in aqueous solution.

Figure 2 shows similar data for polyacrylic acid and Figure 3 for polyvinylamine.

Another element of the composition is an indicator reacting to the exchange of ions. This indicator can be of different types, for example, a pH meter, a pH indicator and other means which can be determined by those skilled in the art. Thus, a pH meter can be used with a typical electrode (in solution systems) or with a surface electrode (in which the composition is incorporated into a support matrix). We can then observe the response of the pH meter for different ion concentrations and we can establish a reference system, a particular change in pH corresponding to a particular ion concentration of a sample; test.

Alternatively, known chromogenic reactive compounds sensitive to pH can be used and these compounds can produce a color change which can be observed by the person carrying out the measurement and who indicates the! - 11 - jl || for testing. If a chromogenic compound is used, a reference coloration system can be established II: 1 so that a rapid visual comparison of the composition and this reference system can provide the desired results. Among the chromogenic substances which can be used: Before the present invention, there are, for example, bromothymol blue, alizarin, bromocresol purple, red! I of phenol and neutral red; we found that the blue of! bromothymol was particularly suitable.

! The present invention also relates to a device in which a support matrix is incorporated into the test composition described in this specification, thus providing a means enabling rapid and reliable assessments of the specific weights of solutions to be obtained. The carrier matrix is usually, but not necessarily, a porous substance such as a sorting paper. Among other types of materials known in the art for this carrier matrix, there are felt, porous strips of ceramic material, same as fibers of | woven or veil glass (United States patent 5,846,247). It is also suggested to use wood, fabrics, spongy materials and clay substances (United States Patent No. 3,552,928). All these materials, as well as others, can be used for the support matrix according to the present invention. The filter paper has been found to be particularly suitable.

In a preferred embodiment, the filter paper is impregnated with a solution or a suspension of a partially neutralized polyelectrolyte in water or other suitable vehicle which can easily be determined afterwards. drying. The filter paper comprising the polyelectrolyte is then impregnated with a solution of the desired indicator element (such as bromothymol blue) in methanol or another suitable solvent such as ethanol, N, N- dimethylformamide and dimethyl sulfoxide, to then carry out drying. Alternatively, a single immersion process can be adopted such that the polyelectrolyte and the indicator element are simultaneously present in the initial solution or suspension.

The dried support matrix comprising the reagents can optionally be installed on a support material. Thus, in a preferred embodiment, the test device comprises a support matrix consisting of a filter paper incorporated in a partially neutralized polyelectrolyte, as well as an indicator element of the type indicated above, this matrix being attached to one side of an elongated piece of transparent polystyrene film. The matrix is attached to one end of the film by any suitable means, for example, a double-sided adhesive tape ("Double Stick", trademark of "3M Company"), the other end of the film polystyrene allowing its grip. In use, this device is held by the free end of the polystyrene film serving as support material and the end of the matrix is immersed in the test sample (for example, urine) from where it is then quickly removed. Any discoloration or other detectable response is observed after a predetermined time and a comparison is made with a reference standard corresponding to responses at concentrations I, i - 13 - dd The particular reference standard adopted depends on the characteristic according to which the composition is used as it is or incorporated into a support matrix, as well as of the particular indicator element. Thus, if we add the partially neutralized polyelectrolyte directly to the test sample and if the indicator element is a pH meter, we can establish a reference standard by adding a standard weight of polyelectrolyte to a typical volume of a solution of known ionic concentration The change in pH is recorded before and after the addition | · Polyelectrolyte using the pH meter. This method is adopted for a series of solutions having different known ionic concentrations. In order to determine the ionic concentration of an unknown test sample, one

adopt the same process and compare the change in pH

; ; with those of known solutions.

i When using a test device comprising a support matrix containing a partially neutralized polyelectrolyte and a chromogenic substance, a * * reference standard may consist of a series of i colored boxes reproducing the color developed by the £ support matrix after a predetermined period of time in

It responds to solutions before known ionic concentrations. When testing an unknown sample,

I plunge the support matrix of a test device into the sample, remove it and observe the appearance or> the change in color after the predefined time period. We then compare the possible colored response t: with the colored boxes serving as reference standards for determining the ionic concentration or the specific weight to better understand the implementation and the implementation of the present invention. This is how we describe and analyze preferred embodiments. It is understood that these examples are given solely by way of illustration and that they in no way limit the scope of the invention as it is described and claimed in this specification.

A. COMPOSITION

Example I - Partial neutralization of a copolymer of maleic anhydride and methyl vinyl ether.

This experiment is carried out to study the partial neutralization of a polyelectrolyte ("Gantrez S-97", trademark of "General Aniline and Film Corporation"), as well as its effect on a composition intended to measure the specific weight of a solution .

A modular automatic titration element is assembled in order to titrate different polyelectrolytes and thus carry out studies relating to the present invention. This titration element consists of an automatic pipetting device, model no 25000 from "Microdemic Systems, Inc.". This instrument can distribute a constant volume of titration product per unit of time in the solution of the polymer to be titrated. The rate of addition of the titration product (and hence the rate of neutralization of the polyelectrolyte) is adjusted by choosing the volume of the pipette, the fraction distributed from the volume of the pipette and the concentration of the titration product. Changes in pH are detected during titration using a standard electrode and a digital "Orion" model 701 pH meter. The output of the pH meter is fed to a 254 mm diagram recorder, model 17500A from "Hewlett-Packard" of which - 15 - 25.4 mm corresponds to a change of one pH unit.

i Therefore, this recorder is equipped with a connected device.

, î continuously trolling the changes occurring in the I "

IpH vis-à-vis the elapsed time (and therefore vis-à-vis the volume of the titration product added).

This device is used to titrate and observe the effects of partial neutralization on "Gantrez S-97" which is a weakly acidic polyelectrolyte.

A solution of "Gantrez" comprising 20 g of | polyelectrolyte per liter of demineralized water. We deposit! - three 100 ml aliquots of this solution in 250 ml beakers. An aliquot is brought to a normality of 0.1N and another, to a normality of 1.0N with NaCl. No salt is added to the remaining aliquot. By titrating each of these poly-i electrolyte solutions with NaOH IN in a 50 ml pipette at! At the rate of 9 ml of titration product per hour and by recording the change in pH with respect to the volume of the titration product, one can study the titration characteristics of the "Gantrez", as well as the effects of partial neutralization on its ability to differentiate between different ionic concentrations.

| The titration results obtained during this experiment are shown in the form of a graph in FIG. 1. Curve A represents the titration of the poly-

electrolyte to which no salt has been added, curve B

represents the titration of the 0.1 N polyelectrolyte solution in NaCl, while curve C represents the titration of the polyelectrolyte solution containing NaCl 1 at a concentration of 1.0N. The clear separation between the ionic centering on the apparent pK value of the polymer.

Therefore, by observing the degrees of separation between the titration curves, that is to say the pH for a given quantity of titration product, one can establish a maximum evaluation concerning the determination of different values relating to the specific weight. For example, in the areas between a pH of 5 and a pH of 10, there is a greater separation than at other stages of neutralization of the polymer. The curves in Figure 1 indicate that there is optimum separation at a degree of neutralization of the polymer of between about 70 and 95 µm or more (i.e. an addition of about 6 to about 9 ml of the titration product). Not only is this information useful for determining the efficiency of the polymer in aqueous systems, but it also contributes to determining the optimal neutralization of the polyelectrophyte with a view to incorporating a support matrix therein, as will be seen in Example IV below.

The percentage of neutralization of a given polyelectrolyte can be calculated from titration results such as those represented by curve A of the graph in FIG. 1 (titration of the polyelectrolyte, in this case "Gantrez S-97", without adding salt). The percentage of neutralization of the polymer is calculated for a given pH of the titrated solution or polymer by bringing the pH of the solution on the ordinate (vertical axis), by drawing a horizontal line from the vertical axis to curve A and by drawing a vertical line from this point on curve A to the horizontal axis (i.e. the number of milliliters of NaOH IjON). The volume of the titration product (corresponding to the intersection of the vertical line and the horizontal axis), t ·, - 17 -

U

f [j 1 and multiplied by 100, gives a close approximation of the | jjj percentage of neutralization of the polyelectrolyte. Point ! · Final titration is indicated by the vertical linearity of curve A on the far right and can be expressed in terms of the volume of the titration product added. This is how .

that, for the "Gantrez S-97", the end point indicated in FIG. 1 is very close to 9 (approximately 8.6) ml of the titration product of NaOH 1, QN. The titration of the "Gantrez" solution in demineralized water at a pH of approximately 7.5 corresponds to a volume of approximately 6 ml of titration product. Since the end point is approximately 8.6 ml of titration product, the percentage of neutralization is calculated by the formula: 6.0 ml (titration product nn ro dd - + oz — trd · * d ... . 6 x 100 = 70 (ml of product 8.6 ml (titration product * ·

at the end point) J

Example II - Partial neutralization of polyacrylic acid This experiment is carried out to study the partial neutralization of polyacrylic acid and the effects of this neutralization on the usefulness of this polyelectrolyte when determining the specific gravity of a solution. The same method is adopted, as is the same modular automatic titration apparatus, the same pH meter and the same electrode as those described in Example I.

A solution of polyacrylic acid (weakly acidic polyelectrolyte sold by "Aldrich Chemical Co.", catalog no. 19.205-8) is prepared by dissolving 20 g of the polymer in 1 liter of demineralized water. We deposit parts | 100 ml aliquots of this solution in 250 ml c beakers. One of the aliquots is brought to a normality 0,1 of 0.1N and another, to a normality of 1.0N in NaCl.

In the third aliquot part, no salt is added.

18 - t in a 50 ml pipette and at the rate of 3 ml of titration product per hour. The results are shown in .figure 2 in which curve A represents the polyelectrolyte solution containing no salt, while curve B represents the solution brought to a normality of 0.1N in NaCl, curve C representing the solution brought to a normality of 1.0N in NaCl.

The results shown in FIG. 2 demonstrate that the strongest separation is obtained with regard to the ionic concentration (that is to say between the "curves A, B and C) when the polymer is neutralized between approximately 501 and about 951 or more (ie an addition of about 1.5 to about 3 ml of titration product). This is how, for example, when the polymer is titrated during "over a period of 40 minutes (with 2 ml of 10N NaOH), a clear separation of the pH obtained can be observed according to the ionic concentration of the solution. Curve C which corresponds to a normality of 1.0N in NaCl, gives a pH of approximately 5.25, curve B, which corresponds to a normality of 0.1N in NaCl, gives a pH of approximately 5.8 and curve A, which corresponds to a zero concentration of NaCl, gives a pH approximately 6.25, therefore the ionic concentration or the specific gravity of a particular solution can be estimated approximately by using these values and establishing an interpolation between them.

Example III - Partial neutralization of polyvinylamine.

This experiment is carried out to study the partial neutralization of a weakly basic polyelectrolyte (polyvinylamine sold by "Dynapol, Inc."), as well as the effects of this neutralization on the utility of this - 19 -

We adopt the same process, as well as the same device! modular automatic titration, the same pH meter and the same I. electrode as in example I.

û v *! | A polyvinylamine solution is prepared in the form of its hydrochloride salt (completely neutralized) having a molecular weight of approximately 60,000 and with a polymer concentration of 20 g / liter of demineralized water. Three 100 ml aliquots of this solution are deposited

In 250 ml beakers. One of the aliquots is brought to a normality of 0.5N and another, to a normality of 3, ON in NaCl. In the third aliquot part, no salt is added. Then, each of these <1 I solutions is titrated with 1.0N NaOH using a 50 ml pipette and at the rate of 9 ml of titration product per hour.

”The results obtained are shown in Figure 3 in which jj curve A represents the titration of the electrolyte poly- I solution to which no salt has been added, while curve B represents the solution brought to a normality 0.5N in NaCl, curve C representing the titration of the solution brought to a normality of 3, ON in NaCl.

The results of FIG. 3 demonstrate that there is hardly any response with regard to the ionic concentration when the polymer is completely in the form <. _ ammee or not neutralized (pH: 10; 35 minutes), while! "J 1 we obtain an excellent separation at 11 degrees. lower titration, i.e. when neutralization i; I *; I 'of the polymer is more advanced. Therefore, the altitude of: ï ΐ, polyvinylamine to differentiate between different ionic concentrations varies inversely with the amount of product! s! i of titration so that at the start of the titration (more than 95¾ of - 20 - that, at zero separation (addition of approximately 5.3 ml of titration product), there is no separation .

B. TEST DEVICE

Example IV - Yield of a copolymer of maleic anhydride and methyl vinyl ether in a support matrix.

The solution used in Example I (20 g of "Gantrez S-97" per liter of demineralized water) is subjected to additional studies in order to observe its behavior in? measuring the specific weight of urine when it is incorporated into a support matrix.

A test device sensitive to ionic concentration or specific gravity is prepared by incorporating the solution of "Gantrez S-97” in a filter paper and then drying. Several test devices are prepared in order to study the yield polyelectrolyte at different degrees of neutralization. This is how we neutralize aliquots of the solution of "Gantrez S-97" to different degrees by titration with NaOH. Dip strips of filter paper from the firm "Eaton and Dikeman" (No. 204) in these partially titrated aliquots, then dried, then immersed impregnated and dried strips obtained from each of these aliquots respectively in urine having different known specific weights , as well as in demineralized water, then measure the pH. To carry out these measurements, use a pH meter comprising a planar surface electrode supplied by "Markson Science, Inc." (N ° -1207 "Bac tiMedia "combination pH / reference electrode). The table below shows the values "ΔρΗ", that is to say the difference in pH in identical strips immersed i,, - 21 - ΐ of a known specific gravity.

pH of the parts Values ^ pH supplied by aliquots of the urine having the specific weights indicated; polyelectrolyte solution Specific weight Specific weight Specific weight 1.030 fique 1.015 fique 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 results of the table above are shown in the form of a diagram in FIG. 4 where the three curves represent the ΔpH values supplied by urines having the specific weights indicated by practicing the tests with i strips formed from aliquots having | different degrees of neutralization. From FIG. 4, it can be seen that the degree of separation of the curves increases markedly when the degree of neutralization of the; | | polyelectrolyte, that is, the pH, rises. Consequently, the greater the partial neutralization of the "Gantrez" polyelectrolyte, the stronger the ability to differentiate between the specific weights of the urine.

Example V - Yield of polyacrylic acid in a | .

1. support matrix.

.

J The polyelectrolyte used in Example II (20 g of polyacrylic acid per liter of demineralized water) is subjected to additional studies with a view to observing; . ver its behavior when measuring the specific weight of urine with incorporation into a support matrix.

• i Test devices are prepared and - ° ° - except that polyacrylic acid is substituted for "Gantrez S-97". A solution of 20 g of polyacrylic acid is prepared per liter of demineralized water. Aliquots of this solution are titrated with 10N sodium hydroxide until the pHs indicated in the table below are obtained. These strips of filter paper from the firm "Eaton and Dikeman" (no. 204) are respectively immersed in these aliquots and dried.

Then, they are respectively immersed in urine with different known specific weights, as well as in: demineralized water, then the pH is measured. The Δ pH values are determined as described in Example IV; these values are listed in the table below. To carry out these measurements, a pH meter with a planar surface electrode from the firm "Markson Science, Inc." is used. (n ° 1207 "BactiMedia" pH / reference electrode combination).

pH of the parts Values ΔpH supplied by aliquots of urine of the having the specific weights indicated solution of the poly- electrolyte Specific weight Specific weight Specific weight 1.005 fique 1.015 fique 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

The results of the table above are shown in the form of a diagram in FIG. 5 which, like FIG. 4, demonstrates that the degree of separation of the curves increases markedly as the degree of neutralization! !

EXAMPLE VI Yield of Polyvinylamine in a Matrix support.

\ The polyelectrolyte used is subjected to the example! I · pie III to additional studies in order to observe its behavior when measuring the specific weights of | different urines with incorporation in a sup port matrix.

We are preparing test devices and we are! tests as described in Examples IV and V, with the exception that polyvinylamine is substituted for "Gantrez S-97" and polyacrylic acid, respectively. A solution is prepared comprising 20 g of polyvinylamine (sold by "Dynapol, Inc.", molecular weight: 60,000, see Dawson et al., J.A.C.S. 98, 5996, 1976) per liter of water. demineralized. The polyelectrolyte used is in the form of its hydrochloride and, therefore, it is in the completely neutralized state. Aliquots of this solution are titrated respectively with 1.0N NaOH to obtain the pHs indicated in the table below. We plunge I, respectively, of strips of filter paper from the firm "Eaton and

Diheman "(N ° 204) in these aliquots and · they are dried. Then, they are respectively immersed in different urines I with known specific weights, as well as in demineralized water et and the pH is measured using the plane surface electrode è décrite described in examples IV and V.

P Next, the Δ pH values are determined as described in ifc | · Examples IV and V; the results obtained are shown in the table below.

Γ ^

Uu - 24 - pH of the parts Values ΔρΗ supplied by urine * aliquots of the having the specific weights indicated poly solution -----: - electrolyte Specific weight - Specific weight Specific weight 1.005 fique 1.015 fique 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 -0.53 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

The graph of these results (FIG. 6) indicates ji [that a useful separation is obtained when the polyelectrolyte trolyte is partially neutralized at a pH below about 5. This is how the curve drawn for the urine having a specific gravity of 1.005 indicates a much smaller change in pH than for urine with a specific gravity of 1.030. As can be expected, urine with a specific gravity of 1.015 gives values ΔρΗ inter- | mediaries.

! This effect is demonstrated even more spectacularly when the polyvinylamine test devices are respectively immersed in aqueous saline solutions having different ionic concentrations, as well as in demineralized water and when measured the pH j · to obtain the Δ pH values. Thus, strips prepared as described above are subjected to tests and different concentrations of sodium chloride in demineralized water. These concentrations of the solution (- 25 - i,

The results obtained during this experiment are shown in the table below and in the form of a graph in FIG. 7. Curves A, B and C correspond to saline solutions of 3, ON, 1.5N and 0.5N in NaCl respectively.

pH of the parts Δ pH values obtained with aliquots of the salines having the indicated normalities poly- electrolyte solution 0.5N NaCl 1.5N NaCl 3, ON 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 f 6.0 0.90 0.93 1.03 I 8.0 0, 64 0.64 0.68! 10.0 0.61 0.64 0.60 i; i 11.0 -0.01 -0.03 -0.10 ‘i 12.0 -0.09 -0.22 -0.29 | Referring to Figure 7, at a pH of 10

W

at I to which the polyelectrolyte is essentially non-protonated ij and uncharged, the effect of the variation in the salt concentration is virtually non-existent. However, partial neutralization of the polymer gives rise to a variety of

H

· * Gence constantly increasing in yield in response% to ionic concentration, as demonstrated by the difference _vP ..> ag increasing between the respective curves reflecting one; .. îj f- '' response Δ pH widely different at different concentrations _ ion ions.

Example VII - Test device prepared using a! - copolymer of maleic anhydride and methyl vinyl ether, - as well as bromothymol blue.

i Use the test composition of example] -2 (, - t thymol which is a known pH indicator, in order to study the characteristics of the present invention with regard to the visual determination of the specific weight .

A solution containing 20 g of "Gantrez S-97" is prepared per liter of demineralized water. An aliquot of this solution is titrated with NaOH until the pH of the solution is 8.0, this pH being measured with the pH meter and the electrode described in Example I. filter paper strip ("Eaton and Dikeman No. 204") in the partially titrated (neutralized) aliquot part, then dried. The dried strip containing the polymer is then immersed in a methanolic solution of bromothymol blue at a concentration of 1.2 g / liter. After drying, install the strip of filter paper on a clear plastic support ("Trycite" from the company "Dow Chemical Co.") using a double-sided adhesive tape ("Double Stick", from the "3M Company "). The test devices obtained each consist of a "Trycite" strip measuring approximately 88.9 x 5.08 mm, one end of which has a square of impregnated filter paper measuring 5.08 mm on a side. The rest of the strip of "Trycite" is used for its gripping.

The sensitivity of these test devices to test weight is studied by testing with three urine samples having different test weights, as well as with water. A device is immersed in the particular test solution and quickly removed therefrom. After 60 seconds, the device is examined with a spectrophotometer with reflecting power, which scans and measures the intensity of the light reflected by this arrangement. - 27 - i _ half seconds.

The results obtained at 60 seconds are taken up in the form of a diagram in FIG. 8 where a clear separation is observed allowing an easy and precise differentiation of the specific weights between the water (specific weight: 1.000) and urines having specific weights of 1.005, 1.015 and 1.030. Visual differentiation of colors is also easy, the device giving a blue color with water, a blue-green color with urine with a specific weight of 1.005, a green color with a specific weight of 1.015 and a yellow color. at a specific weight of 1.030.

This example demonstrates the relationship between partial neutralization of the polyelectrolyte and the determination of the specific gravity or ionic concentration.

The "Gantrez" solution from which the device is formed, has a pH of about 8. Referring to the curve | In FIG. 1, this pH corresponds to approximately 6.8 ml of titration product. By adopting the calculation described in Example I, this i! result corresponds to a neutralization of approximately 791. The ι ·; h; remarkable differentiation between specific weights in | the example above is due to this relatively high degree I ^ ^ !! high neutralization of the polyelectrolyte.

:! / 1 i I ’i; r

Claims (25)

1. Test composition for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it comprises a polymer forming a weakly acidic or weakly basic polyelectrolyte, this polymer being neutralized at at least about 501, as well as an indicator element capable of producing a detectable response to the ion exchange between this polyelectrolyte and this sample. 2. Composition according to claim 1, characterized in that the polyelectrolyte is polyacrylic acid, polymaleic acid, a copolymer of maleic acid and vinyl methyl ether, polymethacrylic acid a copolymer of styrene and maleic acid , polyvinylamine or poly (4-vinylpyridine). 3. Composition according to claim 1, characterized in that the polymer is a weakly acidic polyelectrolyte. 4. Composition according to claim 1, characterized in that the polymer is a weakly basic polyelectrolyte. 5. Composition according to any one of claims 1 to 4, characterized in that the polymer forming the polyelectrolyte is neutralized at a rate of about "75. about 95¾. 6. Composition according to any one of claims 1 to 4, characterized in that the indicator element is a pH indicator substance. 7. Composition according to any one of claims 1 to 4, characterized in that the element indi- - 29 -}! polyelectrolyte-forming polymer is neutralized for good reason | from about 75 to about 95 ". 8. Composition according to claim 1, fi jj characterized in that the polyelectrolyte is a copolymer i | methyl vinyl ether and maleic acid, while i 5!;! the indicator is bromothvmol blue. 9. Test device for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it comprises a support matrix I incorporated into the composition according to one;) any of claims 1 to 4 or 8. dd 10. Test device for determining i the ionic concentration or the specific weight of a jj aqueous test sample, characterized in that it comprises; J:;! a support matrix incorporated into the composition according to I 'I claim 5. 11. Test device for determining i jj the ionic concentration or the specific weight of a fl I aqueous test sample, characterized in that it comprises S ^ a support matrix incorporated into the composition according to! R * claim 6. i (d 12. Test device for determining | f ^ the ionic concentration or the specific gravity of a | aqueous test sample, characterized in that it comprises | a support matrix incorporated into the composition according to claim 7. i; j, 13. Method for determining the ion concentration or the specific gravity of a test sample? * aqueous, characterized in that it consists in bringing this sample, till into contact with the composition according to any one - 30 - 14. Method for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it consists in bringing this sample into contact with the composition according to claim 5 and observing a detectable response. 15. Method for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it consists in bringing this sample into contact with the composition according to claim 6 and observing a detectable response. 16. A method for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it consists in bringing this sample into contact with the composition according to claim 7 and observing a detectable response. 17. Method for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it consists in bringing this sample into contact with the device according to claim 9 and observing a detectable response. 18. A method for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it consists in bringing this sample into contact with the device according to claim 10 and observing a detectable response. 19. Method for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it consists in bringing this sample into contact with the device according to claim 11 and observing a detectable response. - 31 - ί 20. Method for determining the ionic concentration or the specific weight of an aqueous test sample i, characterized in that it consists in bringing this sample into contact with the device according to claim 12 and observing a response detectable. 21. Method for preparing a test device for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it comprises the steps which consist in neutralizing at least 501 of the ionizable groups of a poly- | mother forming a weakly acidic or weakly basic polyelectrolyte • and incorporating this polymer and a pH indicator into a: support matrix. i i 22. The method of claim 21, charac terized in that the polymer forming the polyelectrolyte is neutralized in an amount of about 75 to about 95¾. 23. Method according to any one of claims 21 and 22, characterized in that the polymer and the pH indicator are incorporated into the matrix by combination with an appropriate solvent to form an impregnation mixture, then this support matrix is brought into contact with this mixture and then dried. 24. A method of preparing a test device for determining the ionic concentration or the specific weight of an aqueous test sample, characterized in that it comprises the steps which consist in preparing an aqueous solution of a copolymer of maleic acid and methyl vinyl ether, add an aqueous solution of a base to this solution of the copolymer in an amount sufficient to neutralize at least 50¾ of the acid groups of this - 7> 2 - solution of the partially neutralized polymer so to incorporate this polymer into this matrix, dry the matrix in which the polymer is incorporated and incorporate a pH indicator into the dried matrix. 25. The method of claim 24, characterized in that the pH indicator is bromothymol blue, while this indicator is incorporated into the dried matrix in which the polymer is incorporated by preparing a solution of this indicator in methanol and by putting this matrix in which the polymer is incorporated, in contact with this solution of the indicator. r \ \ V \ V \ .. V, f v \ \ \ \ \ \ \ * *