JPH1019873A - Composition for measuring specific gravity of liquid sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the determining of specific gravity in the strict sense by lading a non-ionic solute with an ionizing agent capable of ionizing the non-ionic solute present in a liquid sample and measuring the non-ionic solute with an ionic solute. SOLUTION: An ionizing agent capable of ionizing a non-ionic solute present in a liquid sample can be laden with a composition for measuring the specific gravity of the liquid sample formed of an anion type ion associative reagent and cation type ion associative reagent. The anion type ion associative reagent used in this composition is a polymer or chain compound with a sulfonic group, sulfate group, or phosphate group. On the other hand, the cation type ion associative reagent is basic pigment which is not discolored in the range of pH4-9(the pH that regular urine indicates) e.g. thiazine pigment, oxazine pigment, azine pigment, triphenylmethane pigment, diphenylmethane pigment, azo pigment, etc., to name a few.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for measuring the specific gravity of a liquid sample and a test piece using the composition. The measurement of the specific gravity of a liquid sample is performed in a wide range of technical fields. In particular, measuring the specific gravity of urine is one of important items having high clinical significance in the field of clinical examination, and is used for diagnosis of kidney disease and the like.

[0002]

Problems of the prior art The urine specific gravity of a healthy person is usually 1.005.
It varies widely from 1.030 to 1.015 in 24-hour urine
The value before and after. As a measuring method of urine specific gravity, there is a physical measuring method using a liquid hydrometer, a urine specific gravity meter, a pycnometer, a refractometer or an osmometer. In addition, a measurement method using a specific gravity measurement test paper or measurement piece composed of a porous resin material or a plurality of beads has been disclosed [1] [2]. However, these methods have problems such as an expensive instrument, complicated operation and time-consuming measurement, and a complicated structure of a measuring piece.

[0003] On the other hand, in the field of clinical examination, in the measurement of a component in a body fluid sample such as urine, a dry-type reagent test piece is used to perform the measurement operation easily and quickly at low cost. The test piece is brought into contact with the body fluid sample, and by observing the color change of the test piece caused by the reaction between the various components in the sample and the reagent component in the test piece, it is easy and quick without using any special equipment. Analysis is possible. This method has been widely used because color change can be visually confirmed and quantitative measurement can be performed by using a simple device such as a color analyzer.

The relationship between the ionic strength and the specific gravity of a liquid sample has already been clarified [3], so a description thereof will be omitted, but it is known that the ionic strength and the specific gravity are particularly well correlated and proportional to urine. I have.

A method has been proposed in which the ionic strength of a liquid sample is measured by colorimetric analysis utilizing this relationship to determine the specific gravity. The following briefly describes the ionic strength measurement techniques that have been proposed so far. First, a method using osmotic pressure gradients inside and outside microcapsules [4] was reported. This method has problems that it is easily affected by temperature, it is difficult to make a judgment, and it is difficult to produce a dry type test piece based on this principle. A method using the change in the water absorption of the swellable resin [5] is known, but it is still susceptible to temperature, and it is difficult to maintain a uniform quality test piece based on this principle. Problem. Other applications include the application of the ion exchange effect of weak electrolyte polymers [6], the application of the ion exchange effect of quaternary ammonium salt polymer electrolytes [7], and the application of the ion exchange effect of complexing agents [8]. Attempted. These test pieces based on the prior art have solved the manufacturing problems, but because the reagent component is a weak electrolyte, the charge of the polymer and the like depends on the pH, and as a result, the measured value is affected by the urine pH. It will be easier. PH, especially in highly buffered alkaline urine
There is a problem that needs to be solved, such as the necessity of correction.

Therefore, the applicant of the present application has proposed a simpler method for controlling the pH of a liquid sample by utilizing the salt inhibition phenomenon on the ion association reaction between an anion-type ion-associating reagent and a cation-type ion-associating reagent (dye). We have found that it is possible to manufacture test pieces that are not affected by temperature, measurement time, etc. [9]. We also proposed a measurement technique that further improved this technique to reduce the tendency for color difference to decrease in the high specific gravity region [10]. Similar techniques have been reported elsewhere [11].

By improving the influence of pH and the quantitativeness in a high specific gravity region in this way, a measurement technique having no problem in measuring ionic strength has been realized. By the way, as described above, for example, when urine is used as a sample, the ionic strength of urine has a correlation with the specific gravity, and it is considered that the measurement of ionic strength is meaningful even from a clinical viewpoint. However, to determine the specific gravity of a liquid in a strict sense, the nonionic solutes contained in the sample should also be measured. Urine is always excreted in urine of mammals including humans. Although urea is present at concentrations that affect the specific gravity of urine, it has not been reflected in previous measurements.

On the other hand, there has been reported an attempt to ionize a nonionic solute such as urea and measure the ionized solute using a composition for measuring ionic strength [4]. In this report, the microcapsules introduced earlier as a composition for measuring ionic strength were used to ionize nonionic solutes such as urea and glucose contained in urine to reflect the measured values. Has become. However, when microcapsules are used as in this report, there is a difficulty in manufacturing when processing into test pieces. On the other hand, in the case where a weak electrolyte or the like, which is easy to produce, is used, there is a feature that it is easily affected by pH, so that it may not be able to be combined depending on ionizing agents. For example, when urea present in a large amount in urine is ionized by urease, the pH of the reaction solution increases due to the production of ammonia, and it becomes impossible to obtain a correct measurement value.

Apart from the relationship between nonionic solutes and specific gravity,
There are inherent problems when using a urine sample as a sample.
It is known that when a urine sample is left at room temperature for a long time after excretion, urea is decomposed by the action of bacteria to produce ammonia. In a conventional reagent composition for measuring cations, the measurement value is affected by the ammonia thus generated. At present, fresh urine is used for the test, and if the test cannot be performed immediately, it is stored at the lowest possible temperature to avoid the effects of ammonia.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new technique capable of determining a specific gravity in a more strict sense by measuring a nonionic solute together with an ionic solute. . Another object of the present invention is to provide a new specific gravity measurement technique that is easy to manufacture even when applied to a test piece and is not easily affected by the pH of a sample.

[0011]

An object of the present invention is to provide a composition for measuring the specific gravity of a liquid sample comprising an anion-type ion-associating reagent and a cation-type ion-associating reagent, wherein the composition is present in the liquid sample. The problem is solved by a composition for measuring the specific gravity of a liquid sample, which comprises an ionizing agent capable of ionizing a nonionic solute.

The anion-type ion associating reagent used in the composition of the present invention is a polymer or a chain compound having a sulfonic acid group, a sulfate ester group or a phosphate ester group. Examples of the polymer include sodium dextran sulfate, Examples include sodium heparin, sodium chondroitin sulfate, sodium cellulose sulfate, and nucleic acids. On the other hand, examples of the chain compound include sodium dodecyl sulfate and sodium dodecyl benzene sulfonate. Because these polymers or chain compounds are strong electrolytes, they can always be present in an anionic state in solution over a wide pH range.

The cationic ion associating reagent used in the composition of the present invention is a basic dye which does not discolor in the range of pH 4-9 (the pH indicated by ordinary urine), for example, thiazine dye, oxazine dye, Examples include azine dyes, triphenylmethane dyes, diphenylmethane dyes, and azo dyes. The following compounds can be listed as examples of the basic dye which is a cationic ion-associating reagent. Acriflavine Acridine Yellow Acridine Red Acridine Orange Astrazone Orange R Astrazone Blue Astrazone Brilliant Red 4G Astrazone Pink FG Astrazone Red 6B Azure A Azure B Ethyl Violet Auramin Cresyl Violet Crystal Violet Safranin O Thiopironin Thion Thioflavin T O-Toluidine Blue Nile Blue O Night Blue R New Methylene Blue Neutral Red Neutral Violet New Fuchsin Pyronin G Pyronin B Victoria Blue Brilliant Green Brilliant Cresyl Blue Fuchsin Basic Yellow 11 CI Basic Blue 3 Hoffman's Violet Malachite Green Methylene Blue Methylene Lean methyl violet methyl green Rhodamine B Rhodamine 6G Janus green Janus red Janus Yellow R Janus Blue G

In the present invention, the concentration of the anion-type ion associative reagent is suitably 0.001 to 10%, particularly preferably 0.005 to 5%, in the impregnating solution when a dry test piece is used.
Is preferred. The concentration of the cation-type ion associating reagent is also suitably 0.0001 to 5% in the impregnation solution, and particularly preferably 0.001 to 1%. The mixing ratio of both reagents is
It is appropriately selected according to the types of both reagents and the type of the test liquid to be measured. (% Means weight / volume% unless otherwise specified).

As will be described later, the ion-associative reagents, which are the basic reagent composition for measuring ionic strength in the present invention, cause a color change based on a reaction principle called metachromism. The color change of the pigment based on metachromatic is not due to the change in pH of the aqueous solution,
This is due to a change in the electronic state of the reagent. Therefore, the reagent composition for measuring ionic strength used in the present application is hardly affected by pH. Therefore, addition of a buffer or pH correction is not necessary for normal urine (pH 4-9).

However, since some of the samples actually encountered have a special pH, the pH of the reaction system may be changed as necessary.
Can be added in a predetermined amount so that the pH falls within the range of 5-10. Examples of the pH buffer include conventional ones such as phosphate, nitrate, carbonate, citrate, diethylmalonate, and aminoalkylsulfonate derivatives. Other specific examples of buffers that can be used in the present invention include acetate, bicine, phthalate, borate, trichloroacetate, sulfosalicylate, tartrate, and succinic acid. salt,
Maleic acid, 2,2-bis (hydroxymethyl) -2,
2 ′, 2 ″ -nitrilotriethanol, 3,3-dimethylglutaric acid, 3-N-morpholinopropanesulfonic acid (MOPS), malonic acid, 1,3-bis [tris (hydroxymethyl) methylamino] propane (ie, ,
Bis-tris), tris (hydroxymethyl) aminomethane (ie, Tris), tris (hydroxymethyl) aminomethane-maleic acid (ie, tris-maleate), tris (hydroxymethyl) aminomethane-malonic acid (ie, , Tris-malonate), 3-
N- (trishydroxymethyl) methylamino-2-hydroxypropanesulfonic acid (TAPSO), 2-
([Tris (hydroxymethyl) methyl] amino) ethanesulfonic acid (TES), 1,4-piperazinebis (ethanesulfonic acid) (PIPES), 4-morpholinoethanesulfonic acid (MES), N-2-hydroxyethylpiperazine -N'-2-ethanesulfonic acid (HEPE
S), and other suitable buffers known in the art, or combinations thereof, can be used.

The present invention is characterized in that an ionizing agent capable of ionizing a nonionic solute is used in combination with these basic known compositions for measuring ionic strength. There are various ionizing agents, and it is sufficient to select an ionizing agent that quantitatively generates a cation from a nonionic solute expected to be present in a sample to be measured. If cations cannot be generated in one step, it is also possible to induce cations through a multi-step reaction based on a primary reaction product. In the present invention, the nonionic solute to be ionized need not be all the solutes expected to be present in the sample. It suffices if it is possible to ionize those that need to be measured in accordance with the purpose of the analysis. In the following, a case where urease or the like is used to ionize urea in a urine sample will be described as an example.This is because urea in urine is present at a relatively high concentration, and it is considered that the influence on specific gravity is large. It is.

For example, if urine whose specific gravity is often measured in the clinical test field is used as a sample, one of the nonionic solutes to be considered is urea. Urea is a component that is universally present in the urine of mammals including humans,
When measuring the specific gravity of urine, it is the first non-ionic solute to be considered. Urea is 14 to 21 g a day for normal adults
Is excreted in the urine [12]. The amount fluctuates and is a component that cannot be ignored when considering the specific gravity. As the urea ionizing agent, substances having a hydrolytic action such as urease and urea amidolyase are known. Urease is a type of amidase (EC 3.5.1.) That catalyzes a reaction that hydrolyzes urea [CO (NH ₂ ) ₂ ] to produce two molecules of ammonia.
5.) Bean, Bacillus, and Methyl
Urease from ophilus is commercially available. Any of these ureases can be used in the present invention.

On the other hand, urea amidolyase is a hydrolase (EC 3.5.1.) That catalyzes a reaction that finally produces two molecules of ammonia from urea through a plurality of reactions in the presence of ATP.
45). Those derived from fungi of the genus Candida are commercially available. When urea amidolyase is used as a urea ionizing agent, it must be used together with ATP, which is a coenzyme.

The ionizing agent used in the present invention is used at a concentration effective for ionizing a nonionic solute expected to be present in a sample. In view of the possibility that the concentration of the nonionic solute fluctuates, and that the ionization proceeds as quickly as possible, it is advantageous to use an excess of the ionizing agent.
Specifically, for example, when urine is used as a sample, a practical reaction rate can be expected at room temperature by using about 0.003 U of urease per 1 ml of the reaction solution.

In the present invention, a known auxiliary component [10] can be combined in order to improve the quantitativeness of the basic composition for measuring ionic strength in a high specific gravity region. As these auxiliary components, substances having an oxyethylene group are known. Specific examples include polyethylene glycol, crown ethers, and nonionic surfactants having an oxyethylene group. In the present invention, ions generated by the ionizing agent are measured in addition to the ionic substances originally present in the sample. Therefore, the use of auxiliary components to improve the quantification in these high concentration ranges is an advantageous embodiment.

The polyethylene glycol has a molecular weight of 1
Those having a molecular weight of 3,000 to 500,000 are preferred, and those having a molecular weight of 3,000 to 500,000 are particularly preferred. Examples of the crown ether suitable for the present invention include 18-crown-
Examples include 6-ether, 15-crown-5-ether, and 12-crown-4-ether. Furthermore, nonionic surfactants having an oxyethylene group include:
Many things are known. In the present invention, those having excellent water solubility are particularly useful. For example, those commercially available under trade names such as Triton, Tween, and Bridge are all preferable surfactants that can be used in the present invention. These substances having an oxyethylene group may be used alone or in a combination of two or more. The addition amount of the substance having an oxyethylene group is appropriately selected according to the type and combination of the anion-type ion associating reagent and the cation-type ion associative dye, and the amount of water absorbed by the absorbent carrier. 0.01% ~
A concentration range of about 10% is preferred.

The composition for specific gravity measurement of the present invention can be provided in the form of a solution, in a dry state, or in a state of being impregnated with a suitable absorbent carrier. In the case of a reagent composition provided in a solution state or a dried state, the specific gravity can be determined by directly mixing or appropriately diluting a liquid as a sample, and observing a color change of the reaction solution. When using a sample impregnated in an absorbent carrier, the sample is also brought into contact with the absorbent carrier as it is or after dilution,
Observe the color change.

The absorbent carrier used in the present invention can be used as a test piece by itself, and can be formed on a suitable support such as a plastic sheet such as polystyrene, polyvinyl chloride or polyester. It can also be used as a test piece by sticking one having a shape.
Further, a hydrophilic polymer such as starch or polyvinyl alcohol is used as an absorbent carrier / adhesive, and the composition of the present invention mixed therewith is applied to a support such as the plastic sheet, and then dried and fixed to form a test piece. May be manufactured. The support may be provided with a color, a symbol, a character, a figure, a pattern, or the like as desired in order to facilitate determination of a measured value. The color change can be observed with the naked eye, or can be measured mechanically as a change in absorbance or reflected light intensity. When performing optical measurement mechanically, it is preferable to use a wavelength at which the amount of change is greatest in accordance with the characteristics of the dye component constituting the reagent. At this time, for a colored sample such as urine, a more accurate value can be obtained by correcting the measured value with the optical measured value of the sample itself.

When mechanically measuring the color change on the surface of the test piece, an analyzer called a color analyzer can be used. The extinction coefficient (K), scattering coefficient (S), and reflectance (R) at an appropriate measurement wavelength are measured by a color analyzer, and the calculation formula “K / S = (1-
The specific gravity can be calculated by calculating the K / S function based on “R) ² / 2R” and comparing the K / S function with the K / S function of the standard sample previously obtained in the same manner. The K / S function is obtained by Kubelka-Munk theoretically deriving the relationship between K / S and R in order to determine the reflectance of a painted surface or a woven fabric.

The present invention further provides the following specific gravity measuring method using an ionizing agent. That is, the present invention
In a method for measuring the specific gravity of a liquid sample by mixing a solution containing an anion-type ion-associating reagent and a cation-type ion-associating reagent with a liquid sample, and measuring the absorbance of the solution, the solution is present in the liquid sample. Provided is a method for measuring the specific gravity of a liquid sample, characterized in that both are mixed after or in the presence of an ionizing agent capable of ionizing a nonionic solute.

According to the present invention, a liquid sample is brought into contact with a specific gravity measurement test piece composed of a liquid absorbent carrier holding an anion type ion associative reagent and a cation type ion associative reagent. In the method for measuring the specific gravity of a liquid sample by observing a color change, whether an ionizing agent capable of ionizing a nonionic solute present in the liquid sample is held in the liquid absorbing carrier in advance, Alternatively, there is provided a method for measuring the specific gravity of a liquid sample, which is brought into contact with a liquid sample previously treated with the ionizing agent. In these measurement methods, the ionizing agent may be allowed to react on the sample in advance and then reacted with the composition for measuring ionic strength, or may be mixed with the composition for measuring ionic strength and reacted simultaneously with the sample. Can also.

By the way, when an ionizing agent for ionizing urea is applied to the present invention, the composition provided by the present invention can be used as a composition for measuring urea. That is, the present invention provides a composition for measuring urea in a liquid sample, which contains the following components a) to c). a) Anion-type associative reagent b) Cation-type ion-associative reagent c) Ionizing agent that quantitatively generates cation from urea

Further, the present invention also provides a method for measuring urea including the following steps i) to ii). i) a step of bringing a solution containing urea into contact with an ionizing agent to quantitatively generate cations from urea; ii) an ion association of the generated cations with an anion-type ion-associating reagent and a cation-type ion-associating reagent Of observing the change in color tone caused by interfering with the image

When the present invention is used as a technique for measuring urea, the basic operation and reagent composition are the same as those for measuring specific gravity. However, it is necessary to correct the measured value by the value measured without the urea ionizing agent so that the measured value is not affected by other ionic solutes. For this purpose, a method of separately obtaining and correcting the value of the reagent composition not containing the ionizing agent, or mixing the reagent composition excluding the ionizing agent with the sample in advance and terminating the ionization after terminating the discoloration reaction due to the ions. It is advisable to adopt a method of adding an agent and observing discoloration due to urea. In addition, when a cation that coexists with urea can be specified in advance, the influence on the measured value can be reduced by using a complex that coordinates the cation. Needless to say, such consideration is not necessary for a sample in which cations other than urea are unlikely to be present.

[0031]

The present invention provides a reagent composition for measuring ionic strength which is based on the fact that salts affect the ion association between an anionic ion-associated reagent and a cationic ion-associated reagent (dye). Then, the cation concentration in the liquid sample is measured. Ion association is the binding of anions and cations without coordination bonds [13] [14], and the change in color tone of the dye due to ion association is metachromism (discoloration reaction).
Called [15]. Cation-type ion-associating reagent (dye)
The electron state changes by ion-association with the anion-type ion-associating reagent, and the color tone changes accordingly. Several patents have already been filed for measuring ionic strength using ion association [9] [10] [11]. The measurement principle of the present invention is to measure a nonionic solute that cannot originally participate in the reaction by combining an ionizing agent with the ionizing agent.

[0032]

According to the composition for measuring the specific gravity of a liquid sample of the present invention, a measured value reflecting a nonionic solute can be directly obtained. In any of the specific gravity measurement methods applicable to the test strip method reported so far, the specific gravity is determined secondarily by measuring the ionic strength. When this method is applied to urine specific gravity measurement, clinically meaningful values can be obtained, but in principle, fluctuations in nonionic solute concentrations are not reflected in the measured values, so in a strict sense There was a face that could not be said to be a specific gravity measurement.

For example, when human urine is used as a sample, the measured value using the ionic strength as an index and the value of the specific gravity obtained by a refractometer agree well when the urea and ionic strength have a general ratio. However, when the ratio between the two greatly deviates, it deviates. On the other hand, when urea is ionized according to the present invention, the measured value obtained by the refractometer and the measured value using the ionic strength as an index are in good agreement even in a sample whose ratio is largely shifted.

The reagent composition for specific gravity measurement according to the present invention can be easily processed into a test piece type and is not easily affected by pH, and can be freely combined with an ionizing agent. For example, even if the pH of the reaction system increases due to the ammonia generated when urea, which is a nonionic solute contained in urine, is ionized, the measured value of the reagent composition of the present invention is not affected. Although a method of performing specific gravity measurement by combining an ionizing agent with a reagent composition for measuring ionic strength has been known, it is difficult to produce a known reagent composition for measuring ionic strength, or the method is affected by pH. Therefore, the combination with the ionizing agent itself was difficult.

The anion-type ion-associating reagent and the cation-type ion-associating reagent used in the composition of the present invention are of many types and can be used as commercial products, so that various combinations are possible. An optimum composition according to the purpose of use can be easily and inexpensively prepared. Even when the ionizing agent which is a feature of the present invention is combined, the test piece for specific gravity measurement according to the present invention can be easily manufactured.

Another advantage of the present invention is that it is hardly affected by ammonia. As described above, when urine is used as a sample, ammonia may be generated from urea depending on storage conditions. In conventional techniques for measuring cations, the measured value is affected by the produced ammonia. Moreover, the effects of ammonia appear on two aspects: fluctuations in the pH of the urine sample and the fact that ammonia itself acts as a cation. In contrast, in the embodiment in which urease is combined as an ionizing agent in the present invention, urea is converted into ammonia and measured together with ammonia generated during storage, and as a result, the influence of ammonia generated during storage is reduced. A measurement system that is difficult to receive can be realized.

[0037]

【Example】

1. Specific gravity measurement using the composition of the present invention It was confirmed that the change in urea concentration can be measured by the present invention. That is, 100 μl of 150, 90, and 45 mg / ml aqueous urea solutions were added to 3 ml of the reagent composition solution of the present invention having the following composition, mixed well, allowed to stand at room temperature for 10 minutes, and the absorption spectrum of the reaction solution was measured. Shimadzu spectrophotometer UV-265FS was used for the measurement. This urea concentration is 1.03 (urea concentration 15
0 mg / ml), 1.018 (90 mg / ml urea concentration), and 1.009 (45 mg / ml urea concentration).

Methylene blue trihydrate 0.01 mM Sodium dextran sulfate 0.5 μM (Molecular weight 25,000) Urease 0.01% or no urease (Urease: Tokyo Chemical Industry, 312.6 U / mg)

The results are shown in FIG. 1 (invention; with urease),
And FIG. 2 (conventional method; no urease). FIG.
In the figure, the pattern of the absorption curve was different depending on the urea concentration, and it was confirmed that the measurement of the urea concentration was possible. On the other hand, in FIG. 2 in which the ionizing agent (urease) is not used, no change is observed in the optical characteristics even when the urea concentration changes. Therefore, it is apparent that this measurement system cannot obtain a measurement value reflecting a change in specific gravity due to a change in urea concentration.

References [1] JP-A-59-120842 [2] JP-A-59-112151 [3] JP-B-62-12858 [4] JP-B-60-46374 [5] JP-A-62-95462 [6] JP-B-62-12858 [7] JP-A-59-160739 [8] JP-A-2-66451 [9] JP-A-4-315049 [10] JP-A-6-273409 [11] JP-A-6-294790 [12] An Introduction to Shinsei Chemistry by Kunio Nakajima and Shigeo Kashiwama Nanzando 1
2nd edition published on November 2, 992 [13] Bunseki 1, p61-72, 1989 [14] Anal.Sci. Vol.3, p479-488, 1987 [15] Bunseki 3, p82-86, 1990

[Brief description of the drawings]

FIG. 1 shows the results of measurement using a specific gravity measurement reagent composition according to the present invention. The vertical axis indicates the absorbance, and the horizontal axis indicates the measurement wavelength (nm).

FIG. 2 shows the results of measurement using a specific gravity measurement reagent composition containing no ionizing agent. The vertical axis indicates the absorbance, and the horizontal axis indicates the measurement wavelength (nm).

Claims (10)

[Claims] A composition for measuring the specific gravity of a liquid sample comprising an anion-type ion associating reagent and a cation-type ion associating reagent, wherein a nonionic solute present in the liquid sample is ionized. COMPOSITION FOR MEASURING SPECIFIC SPECIFICITY OF LIQUID SAMPLE, INCLUDING IONIZING AGENTS 2. The composition according to claim 1, further comprising a compound having an oxyethylene group. 3. The composition for measuring specific gravity according to claim 1, wherein the liquid sample is urine. 4. The composition according to claim 3, wherein the solute is urea and the ionizing agent is urease or urea amidolyase. 5. A test specimen for specific gravity measurement comprising a liquid absorbent carrier holding the composition for specific gravity measurement according to claim 1. 6. A method for measuring the specific gravity of a liquid sample by mixing a liquid sample with a solution containing an anion-type ion associating reagent and a cation-type ion associating reagent and measuring the absorbance of the solution. A method for measuring the specific gravity of a liquid sample, which comprises mixing an ionizable agent capable of ionizing a nonionic solute present in the sample after or in the presence of the ionizing agent. 7. A liquid sample is brought into contact with a specific gravity measurement test piece composed of a liquid absorbing carrier holding an anion type ion associative reagent and a cation type ion associative reagent, and the color change of this test piece In the method for measuring the specific gravity of a liquid sample by observing, an ionizing agent capable of ionizing a nonionic solute present in the liquid sample is held in the liquid absorbent carrier in advance, or A method for measuring the specific gravity of a liquid sample in contact with a liquid sample treated with an ionizing agent 8. A composition for measuring urea in a liquid sample containing the following components a) to c): a) an anion-type ion associative reagent; b) a cationic type ion-associative reagent; Ionizing agent that produces ions 9. The composition for measuring urea according to claim 8, wherein the ionizing agent is urease or urea amidolyase. 10. A method for measuring urea including the following steps i) to ii): i) a step of bringing a solution containing urea into contact with an ionizing agent to quantitatively generate cations from urea; Observing the color change caused by interfering with the ion association between the anion-type and the cationic ion-associative reagents