Analysis method and analysis apparatus

Abstract

To provide a method for efficiently concentrating an acidic original solution, particularly an acidic original solution containing an analyte having polarity or charge, and subsequently analyzing the analyte with high sensitivity.SOLUTION: An analysis method according to the present invention is for measuring the concentration of the analyte in a raw solution containing the analyte and a solvent. The analysis method includes a concentration step of concentrating the raw solution to obtain a concentrated solution, and a concentration measurement step of measuring the concentration of the analyte in the concentrated solution. The raw solution has a pH of less than 3.0, and the concentration step is performed by a forward osmosis method using a forward osmosis membrane having a separation active layer composed of polyamide provided on a surface of a microporous support layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for the efficient concentration and subsequent sensitive analysis of acidic stock solutions. [Background technology]

[0002] There are cases where an acidic solution containing a trace amount of an analyte needs to be concentrated for analysis, such as when concentrating and analyzing a dilute sample solution containing acetic acid or trifluoroacetic acid in a peptide drug, or when concentrating and analyzing a dilute solution of metal ions containing nitric acid. These concentrations must be carried out while suppressing loss and deterioration of the analyte.

[0003] Commonly known methods for concentration include, for example, distillation and membrane separation. Of these, the distillation method requires heating, which raises concerns about the heat-induced deterioration of the substance to be analyzed. Membrane separation does not require heating and is therefore expected to be a method for concentrating analytes without altering their properties. Known membrane separation methods include those using ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes.

[0004] Ultrafiltration and nanofiltration membranes separate or concentrate by sieving based on molecular weight cutoff, which is generally on the order of several hundred to several thousand, making it difficult to separate or concentrate small chemical species, such as simple elements or ions, using ultrafiltration or nanofiltration membranes.

[0005] The reverse osmosis membrane and the forward osmosis membrane each have the property of allowing only water to pass through. In reverse osmosis, high pressure is applied to a raw solution placed on one side of a reverse osmosis membrane, causing only the water in the raw solution to pass through the reverse osmosis membrane, thereby concentrating the raw solution.In forward osmosis, the difference in osmotic pressure between the raw solution and the draw solution placed through the forward osmosis membrane is used as the driving force, causing only the water in the raw solution to move to the draw solution, thereby concentrating the raw solution. Thus, forward and reverse osmosis allow for the separation or concentration of small size species.

[0006] The prior art has investigated the effect of the pH of the raw solution on concentration by forward osmosis and reverse osmosis. For example, Patent Document 1 discloses a method in which test water having a pH of 3.0 or higher is concentrated by reverse osmosis, and then the metal ion concentration in the test water is analyzed. Furthermore, Non-Patent Document 1 investigates the effect of pH when concentrating pharmaceutically active substances by forward osmosis, and Non-Patent Document 2 investigates the effect of pH when concentrating rare earth elements by forward osmosis. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-156692 [Non-patent literature]

[0008] [Non-Patent Document 1] Separation and Purification Technology 93 (2012) 107-114 [Non-patent document 2] Process Safety and Environmental Protection 126 (2019) 53-59 Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 1 discloses reverse osmosis concentration of a raw solution with a pH of 3.0 to 6.95, but in the examples it only verifies reverse osmosis concentration of a neutral solution. Non-Patent Documents 1 and 2 report that in forward osmosis concentration using a forward osmosis membrane with a separating active layer made of polyamide, electrically neutral analytes are prevented from passing through the forward osmosis membrane regardless of the pH of the raw solution, but the rejection rate of charged analytes by the forward osmosis membrane decreases when the pH of the raw solution changes from neutral to acidic. These non-patent documents speculate that the decrease in rejection rate of analytes with decreasing pH is due to the fact that the carboxyl groups in the polyamide separating active layer are protonated and lose their charge, making it impossible to utilize the electrostatic repulsion of charged substances. Furthermore, both non-patent documents experimentally verify only the raw solution pH range up to 3.0, and do not consider forward osmosis concentration of strongly acidic raw solutions with a pH of less than 3.0.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for efficiently concentrating an acidic stock solution, particularly an acidic stock solution containing a polar or charged analyte, and then analyzing it with high sensitivity. [Means for solving the problem]

[0011] The present invention is as follows.

[0012] Aspect 1: An analytical method for measuring the concentration of an analyte in a stock solution containing the analyte and a solvent, comprising: The analytical method includes a concentration step of concentrating the original solution to obtain a concentrated solution, and a concentration measurement step of measuring the concentration of the analyte in the concentrated solution, the pH of the stock solution is less than 3.0; The concentration step is carried out by a forward osmosis method using a forward osmosis membrane having a separating active layer made of polyamide on the surface of a microporous support layer. Analysis method. Aspect 2: The analytical method according to Aspect 1, wherein the pH of the original solution is 2.5 or less. Aspect 3: The analytical method according to Aspect 1 or 2, wherein the microporous support layer of the forward osmosis membrane comprises one or more materials selected from the group consisting of polyethersulfone, polysulfone, polyketone, polyetheretherketone, polyphenylene ether, polyvinylidene fluoride, polyacrylonitrile, polyimine, polyimide, polybenzoxazole, polybenzimidazole, and polyamide. Aspect 4: The analytical method according to any one of Aspects 1 to 3, wherein the polyamide constituting the separating active layer of the forward osmosis membrane is a polycondensation product of one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides. Aspect 5: The forward osmosis membrane has a salt back-diffusion rate R1 of 0.30 g / (m 2 5. The analytical method according to any one of aspects 1 to 4, wherein the number of times of the reaction is 1 to 2 times or less. Aspect 6: The forward osmosis membrane has a water permeability F1 of 6.5 kg / (m 2 6. The analytical method according to any one of aspects 1 to 5, wherein the number of the first and second electrodes is 1.times.h) or more. Aspect 7: The analysis method according to any one of Aspects 1 to 6, wherein the forward osmosis membrane is a hollow fiber membrane. Aspect 8: The analytical method according to any one of Aspects 1 to 7, wherein in the concentration step, the stock solution is placed or passed through the separation active layer side of the forward osmosis membrane, and a draw solution is placed or passed through the microporous support layer side of the forward osmosis membrane. Aspect 9: The analytical method of any one of Aspects 1 to 8, wherein the analyte in the original solution comprises one or more elements selected from the group consisting of Li, Be, Na, Mg, Al, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Mo, Ru, Rh, Cd, In, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu, Hf, Ir, Pt, Pb, Bi, Th, and U. Aspect 10: The analytical method according to any one of Aspects 1 to 9, wherein the concentration of the target substance to be analyzed in the concentration measurement step is measured by one or more methods selected from the group consisting of chromatography, electromagnetic wave analysis, mass spectrometry, ion analysis, radioactivity analysis, electrochemical analysis, thermal analysis, and X-ray analysis. [Effects of the Invention]

[0013] The present invention provides a method for the efficient concentration and subsequent sensitive analysis of acidic stock solutions containing, inter alia, polar or charged analytes. DETAILED DESCRIPTION OF THE INVENTION

[0014] The analytical method of the present invention comprises: 1. An analytical method for determining the concentration of an analyte in a stock solution comprising the analyte and a solvent, comprising: The analytical method includes a concentration step of concentrating the original solution to obtain a concentrated solution, and a concentration measurement step of measuring the concentration of the analyte in the concentrated solution, the pH of the stock solution is less than 3.0; The concentration step is carried out by a forward osmosis method using a forward osmosis membrane having a separating active layer made of polyamide on the surface of a microporous support layer. It is an analytical method.

[0015] In conventional forward osmosis concentration, when a forward osmosis membrane with a separating active layer made of polyamide is used, if the source solution is acidic, it is thought that the rejection rate of polar or charged analytes in particular decreases, making it difficult to achieve efficient concentration. As mentioned above, this was thought to be because the carboxyl groups in the polyamide separating active layer are protonated and lose their charge, making it impossible to utilize the electrostatic repulsion of charged substances. However, the present inventors discovered that by using a specific forward osmosis membrane, an acidic raw solution containing a polar or charged analyte can be efficiently concentrated, leading to the present invention. The effects of the present invention are maximized when a forward osmosis membrane is used that satisfies at least one of the following conditions: a low salt back-diffusion rate R1 and a high water permeability F1. The reason for this is believed to be that the use of a polyamide that is thought to have a low salt back-diffusion rate R1 and therefore a high degree of cross-linking can suppress hydrolysis of the polyamide by the acidic raw solution, and the high water permeability F1 can shorten the concentration time, thereby reducing the time the polyamide is in contact with the acidic raw solution. However, the present invention is not bound by any particular theory.

[0016] The requirements for the analytical method of the present invention will be explained below in order. The analytical method of the present invention is an analytical method for measuring the concentration of an analyte in an original solution containing the analyte and a solvent, and includes a concentration step and a concentration measurement step.

[0017] "Undiluted Solution" The original solution used in the analytical method of the present invention contains an analyte and a solvent, and has a pH of less than 3.0. The method of the present invention enables efficient concentration of an acidic raw solution, despite the use of a forward osmosis membrane having a polyamide separation active layer. The pH of the original solution may be 2.8 or less, 2.5 or less, 2.2 or less, 2.0 or less, or 1.8 or less.

[0018] <Substances to be analyzed> The analyte contained in the original solution in the present invention is a chemical species that is stable at pH 3.0 or less. The substance to be analyzed may be, for example, a chemical species containing one or more elements selected from the group consisting of Li, Be, Na, Mg, Al, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Mo, Ru, Rh, Cd, In, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu, Hf, Ir, Pt, Pb, Bi, Th, and U.

[0019] The analyte is preferably a polar or charged chemical species, typically an ion, which includes solvated ions, complex ions, and the like. The analyte contained in the original solution in the present invention may be, in particular, an ion containing one or more elements selected from the group of elements listed above.

[0020] <Concentration of the analyte and standard substance> The concentration of the analyte in the original solution may be below the detection limit of the intended concentration measurement, or may be so dilute that the measurement is considered unreliable, without going through a concentration step. From this perspective, the concentration of the analyte in the original solution may be, for example, 0.01 nmol / L (0.00001 μmol / L) or more and 10 μmol / L or less, or 0.001 μmol / L or more and 1 μmol / L or less.

[0021] <Other ingredients> The stock solution in the present invention contains an analyte, a standard, and a solvent. The stock solution may contain other components other than the analyte, the standard, and the solvent. Another component contained in the original solution is typically an acid. The acid may be an organic acid or an inorganic acid. Examples of organic acids include carboxylic acids, amino acids, and sulfonic acids. Examples of inorganic acids include hydrochloric acid (hydrochloric acid), nitric acid, phosphoric acid, sulfuric acid, boric acid, and hydrofluoric acid. The other components other than those mentioned above may be, for example, various compounds, salts, microorganisms, components in living bodies (red blood cells, white blood cells, antibodies, etc.), and the like.

[0022] <solvent> The solvent of the original solution in the present invention may contain one or more selected from water and organic solvents. The solvent of the original solution may be water or a mixture of water and a water-soluble organic solvent, and is typically water.

[0023] 《Concentration process》 In the concentration step in the analytical method of the present invention, the raw solution is concentrated to obtain a concentrated solution. This concentration step is carried out by forward osmosis.

[0024] <Forward osmosis membrane> The forward osmosis membrane used in the present invention may be a composite semipermeable membrane comprising a support layer and a separating active layer provided on the support layer. The forward osmosis membrane is preferably modularized and used in the form of a forward osmosis membrane module. The forward osmosis membrane is preferably in the form of a hollow fiber, since this allows the membrane area per module of the forward osmosis membrane module to be increased. Therefore, the forward osmosis membrane used in the concentration step of the present invention is preferably a hollow fiber composite semipermeable membrane comprising a hollow fiber support layer and a separating active layer provided on one or both sides of the support layer.

[0025] (Support layer) The support layer of the forward osmosis membrane is a membrane for supporting the separation active layer. The support layer itself preferably does not exhibit substantial separation performance. The support layer preferably has micropores on its surface, the pore size of which is preferably 0.001 μm or more and 0.1 μm or less, more preferably 0.005 μm or more and 0.05 μm or less. The structure of the support layer other than the surface is preferably as sparse as possible while maintaining strength in order to reduce the permeation resistance of the permeating fluid. The sparse structure in this area is preferably, for example, a net-like structure, a structure having finger-like voids, or a mixed structure thereof.

[0026] The material of the support layer is preferably one that is not chemically damaged by the monomer solution, raw solution, and the induction solution described below when forming the separation active layer, and that can be molded into a microporous hollow fiber shape. From this perspective, the material of the support layer is, for example, Preferably, the polymer contains, as a main component, one or more selected from polyethersulfone, polysulfone, polyketone, polyetheretherketone, polyphenylene ether, polyvinylidene fluoride, polyacrylonitrile, polyimine, polyimide, polybenzoxazole, polybenzimidazole, and polyamide; More preferably, the main component is one or more selected from polyethersulfone, polysulfone, polyketone, and polybenzimidazole, More preferably, the main component is one or more selected from polysulfone and polyethersulfone, Polysulfone is particularly preferred. In the above, the term "main component" refers to the component that accounts for the largest weight ratio in the entire support layer, and in one embodiment, is a component that accounts for more than 50% by weight of the entire support layer.

[0027] When the support layer is in the form of hollow fibers, the diameter of the hollow fibers is not particularly limited. However, in consideration of film formation stability, ease of handling, and increasing the film area when made into a module, an outer diameter of 100 μm to 3,000 μm and an inner diameter of 30 μm to 2,500 μm is preferred, and an outer diameter of 200 μm to 1,500 μm and an inner diameter of 50 μm to 1,000 μm is more preferred.

[0028] Such a support layer may be produced by, for example, a known dry / wet film-forming method, melt film-forming method, wet film-forming method, or the like.

[0029] <Separation active layer> The separating active layer of the forward osmosis membrane of the present invention comprises a polyamide. The separating active layer may be provided on one or both surfaces of the support layer. When the forward osmosis membrane is in the form of a hollow fiber, the separating active layer may be provided on the inner surface of the hollow fiber support layer to avoid physical damage to the separating active layer. The thickness of the separating active layer of the forward osmosis membrane of the present invention is preferably as thin as possible to prevent pinholes, but is desirably an appropriate thickness to maintain mechanical strength and chemical resistance. From this viewpoint, the thickness of the separating active layer is preferably 0.1 μm to 3 μm, and more preferably 0.2 μm to 2 μm.

[0030] The separating active layer is preferably made of polyamide. The separating active layer made of polyamide is preferably made of a polycondensation product of one or more first monomers selected from the group consisting of polyfunctional amines and one or more second monomers selected from the group consisting of polyfunctional acid halides.

[0031] Examples of polyfunctional amines include polyfunctional aromatic amines, polyfunctional aliphatic amines, monomers having a plurality of reactive amino groups, and prepolymers thereof.

[0032] Polyfunctional aromatic amines are aromatic amino compounds having two or more amino groups in one molecule, and specific examples include m-phenylenediamine, p-phenylenediamine, etc. 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylamine, 3, 3'-Diaminodiphenyl ether, 4,4'-Diaminodiphenyl ether, 3,3' Examples of the diaminodiphenylamine include 4,4'-diaminodiphenylamine, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,4-diaminodiphenyl sulfone, 1,3,5-triaminobenzene, and 1,5-diaminonaphthalene, and these can be used alone or in combination. In particular, one or two members selected from m-phenylenediamine and p-phenylenediamine are preferably used.

[0033] The polyfunctional aliphatic amine is an aliphatic amino compound having two or more amino groups in one molecule, and specifically, for example, Primary amines having a cyclohexane ring, such as 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 4,4'-bis(paraaminocyclohexyl)methane, 1,3-bis-(aminomethyl)cyclohexane, 2,4-bis-(aminomethyl)cyclohexane, and 1,3,5-triaminocyclohexane; Secondary amines with a piperazine ring, such as piperazine, 2-methylpiperazine, ethylpiperazine, and 2,5-dimethylpiperazine; Secondary amines having a piperidine ring, such as 1,3-bis(4-piperidyl)methane, 1,3-bis(4-piperidyl)propane, and 4,4'-bipiperidine; Amines with both primary and secondary amino groups, such as 4-(aminomethyl)piperidine: Other examples include ethylenediamine, propylenediamine, 1,2-propanediamine, 1,2-diamino-2-methylpropane, 2,2'-dimethyl-1,3-propanediamine, tris(2-aminoethyl)amine, N,N'-dimethylethylenediamine, N,N'-dimethylpropanediamine, etc., and these can be used alone or in mixtures. Mixtures of these polyfunctional aliphatic amines with the above-mentioned polyfunctional aromatic amines may also be used.

[0034] Examples of the monomer having a plurality of reactive amino groups include polyethyleneimine, amine-modified polyepichlorohydrin, and aminated polystyrene. As the prepolymer, for example, a prepolymer made of one or more selected from piperazine, 4-(aminomethyl)piperidine, ethylenediamine, and 1,2-diamino-2-methylpropane is preferably used.

[0035] Examples of polyfunctional acid halides include polyfunctional aromatic acid halides, polyfunctional aliphatic acid halides, etc. These may be bifunctional or higher so as to react with polyfunctional amines to form polymers.

[0036] The polyfunctional aromatic acid halide is an aromatic acid halide compound having two or more acid halide groups in one molecule.Specific examples include trimesic acid halide, trimellitic acid halide, isophthalic acid halide, terephthalic acid halide, pyromellitic acid halide, benzophenonetetracarboxylic acid halide, biphenyldicarboxylic acid halide, naphthalenedicarboxylic acid halide, pyridinedicarboxylic acid halide, benzenedisulfonic acid halide, etc., and these can be used alone or in combination.In particular, trimesic acid chloride alone, a mixture of trimesic acid chloride and isophthalic acid chloride, or a mixture of trimesic acid chloride and terephthalic acid chloride is preferably used.

[0037] The polyfunctional aliphatic acid halide is an aliphatic acid halide compound having two or more acid halide groups in one molecule.Specific examples include alicyclic polyfunctional acid halide compounds such as cyclobutanedicarboxylic acid halide, cyclopentanedicarboxylic acid halide, cyclopentanetricarboxylic acid halide, cyclopentanetetracarboxylic acid halide, cyclohexanedicarboxylic acid halide, and cyclohexanetricarboxylic acid halide; as well as propanetricarboxylic acid halide, butanetricarboxylic acid halide, pentanetricarboxylic acid halide, succinic acid halide, and glutaric acid halide.These can be used alone or in combination, and mixtures of these polyfunctional aliphatic acid halides with the above-mentioned polyfunctional aromatic acid halides can also be used.

[0038] The first and second monomers as described above may be dissolved in an appropriate solvent to prepare solutions, which may then be subjected to interfacial polymerization. The solvent for the first monomer is preferably, for example, water or alcohol, or a mixture thereof. Examples of the solvent for the second monomer include hydrocarbon solvents such as n-hexane, cyclohexane, n-heptane, n-octane, n-nonane, and n-decane, and these are preferably used alone or in mixture.

[0039] The interfacial polymerization for forming the separation active layer may be carried out in accordance with a known method. For example, by passing a solution of a first monomer through the inside of a hollow fiber support layer and then a solution of a second monomer through the inside of the hollow fiber support layer, or by passing a solution of a second monomer through the inside of the hollow fiber support layer and then a solution of the first monomer through the inside of the hollow fiber support layer, interfacial polymerization of the first monomer and the second monomer can occur on the inner surface of the hollow fiber support layer, thereby forming a separation-activated transport. After the first monomer solution is passed through, the pressure outside the hollow fiber support layer may be reduced and this reduced pressure state may be maintained for a certain period of time. After the interfacial polymerization, the formed separation active layer may be subjected to a heat treatment at about 100 to 150°C.

[0040] The salt back-diffusion rate R1 of the forward osmosis membrane used in the present invention is 0.30 g / (m 2 ×h). The forward osmosis membrane's water permeability F1 is 6.5 kg / (m 2 ×h) or more. The effects of the present invention are maximized when a forward osmosis membrane is used in which at least one of the salt back-diffusion rate R1 and the water permeability F1, and preferably both, satisfy the above conditions. This is presumably because the use of a polyamide with a low salt back-diffusion rate R1 and therefore a high degree of crosslinking can suppress hydrolysis of the polyamide by the acidic raw solution, and the high water permeability F1 can shorten the concentration time, thereby reducing the time the polyamide is in contact with the acidic raw solution. However, the present invention is not bound by any particular theory. The salt back-diffusion rate R1 and water permeability F1 of a forward osmosis membrane can be estimated by performing forward osmosis treatment using purified water as the feed solution and a 3.5 wt% sodium chloride aqueous solution as the draw solution, with the temperature of each solution at 25°C. Specifically, the salt back-diffusion amount R1 and the water permeability F1 are evaluated by the following methods.

[0041] The feed solution is passed through the separation active layer side of the forward osmosis membrane, and the draw solution is passed through the support layer side, and forward osmosis treatment is performed for a predetermined time. After the forward osmosis treatment has been performed for the predetermined time, the amount of water L (kg) that has moved from the feed solution (purified water) to the draw solution and the amount of NaCl G (g) that has moved from the draw solution to the purified water are measured, and the back-diffusion amount of salt (sodium chloride) R1 is calculated using the following formula (1), and the water permeation amount F1 is calculated using formula (2). In formulas (1) and (2), M is the effective surface area (m ) of the forward osmosis membrane module. 2 ) and H is the processing time (h). R1(g / (m 2 ×h))=G(g) / (M(m 2 )×H(h)) (1) F1(kg / (m 2 ×h))=L(kg) / (M(m 2 )×H(h)) (2)

[0042] In the present invention, it is preferable to produce a hollow fiber support layer module by storing multiple hollow fiber support layers in a suitable housing, and in the state of this support layer module, to carry out interfacial polymerization of the first monomer and the second monomer to form a separating active layer on the inner surface of the support layer to form a hollow fiber forward osmosis membrane module, and then to carry out the concentration step using this hollow fiber forward osmosis membrane module.

[0043] <Inducing liquid> In the forward osmosis method using a forward osmosis membrane, a stock solution is passed through one side of the above-mentioned forward osmosis membrane (preferably the side on which the separating active layer is formed) and a draw solution is passed through the other side, and the difference in osmotic pressure between the two is used as a driving force to move the solvent from the stock solution to the draw solution through the forward osmosis membrane, thereby concentrating the stock solution.

[0044] The draw solution is a liquid that has a higher osmotic pressure than the original solution and has the function of displacing the solvent from the original solution. The inducer solution may be, for example, a solution containing a high concentration of inducer. Examples of the inducer include alkali metal salts, alkaline earth metal salts, ammonium salts, Examples include sugars, monoalcohols, glycols, and water-soluble polymers.

[0045] Specific examples of these include: Alkali metal salts include, for example, sodium chloride, potassium chloride, sodium sulfate, sodium thiosulfate, and sodium sulfite; Alkaline earth metal salts include, for example, magnesium chloride, calcium chloride, magnesium sulfate, etc.; Ammonium salts include, for example, ammonium chloride, ammonium sulfate, and ammonium carbonate; Examples of sugars include common sugars such as sucrose, fructose, and glucose, as well as special sugars such as oligosaccharides and rare sugars; Monoalcohols such as methanol, ethanol, 1-propanol, and 2-propanol; Glycols include, for example, ethylene glycol and propylene glycol; Examples of water-soluble polymers include polyethylene oxide, polypropylene oxide, and copolymers of ethylene oxide and propylene oxide. Each of them can be mentioned.

[0046] The concentration of the inducer in the inducer solution is preferably such that the osmotic pressure of the inducer solution is sufficiently higher than that of the stock solution, and the inducer solution can exert its function of displacing the solvent from the stock solution. For example, when an alkali metal salt or alkaline earth metal salt is used as the inducer, the concentration thereof may be, for example, 10% by weight or more and the saturated concentration or less. The solvent of the draw liquid may contain one or more selected from water and organic solvents. The solvent of the draw liquid may be water or a mixture of water and a water-soluble organic solvent, and is typically water.

[0047] <Concentration method> As described above, in the forward osmosis method using a forward osmosis membrane, a stock solution is placed or passed through one side of the above-mentioned forward osmosis membrane (preferably the side on which the separating active layer is formed), and a draw solution is placed or passed through the other side, and the difference in osmotic pressure between the two is used as a driving force to move the solvent from the stock solution to the draw solution through the forward osmosis membrane, thereby concentrating the stock solution.

[0048] When the stock solution and the draw solution are caused to flow, the flow direction of these may be a parallel flow or a counter flow. The stock solution and the draw solution may be passed over the forward osmosis membrane in a circulation system in which they are each passed over the forward osmosis membrane and then supplied again to the forward osmosis membrane. for example, A concentration system is constructed having a forward osmosis membrane module, a raw solution tank, a draw solution tank, and piping connecting these. The raw solution is supplied from the raw solution tank to the forward osmosis membrane module, and the raw solution after passing through the forward osmosis membrane module is returned to the raw solution tank. The draw solution is supplied from the draw solution tank to the forward osmosis membrane module, and the draw solution after passing through the forward osmosis membrane module is returned to the draw solution tank. The circulation system is a preferred embodiment of the present invention.

[0049] The temperature during concentration is arbitrary, and may be, for example, 0° C. or higher and 50° C. or lower, with room temperature being sufficient. The concentration time may be any time until the concentration of the analyte in the original solution reaches a level at which a reliable measurement can be obtained in the intended concentration measurement.

[0050] 《Concentration measurement process》 In the concentration measurement step, the concentration of the analyte in the concentrated solution obtained in the concentration step is measured. Preferably, the concentration is determined by a method that provides a reliable determination of the concentration of the analyte. Such a method may be carried out by, for example, one or more methods selected from the group consisting of various types of chromatography, electromagnetic wave analysis based on light absorption, mass spectrometry, trace metal ion analysis, radioactivity analysis, electrochemical analysis, thermal analysis, and various types of X-ray analysis.

[0051] In a preferred embodiment of the present invention, the concentration may be measured by, for example, providing a branch pipe in the discharge pipe from the hollow fiber forward osmosis membrane module after the concentration step, and directly sending a portion of the concentrated solution concentrated to the desired concentration to the measuring device.

[0052] According to the analytical method of the present invention, it is possible to efficiently concentrate an acidic raw solution containing a polar or charged analyte, and then analyze it with high sensitivity. Furthermore, the concentration step in the analytical method of the present invention is carried out by forward osmosis, and therefore does not require heating of the original solution. Therefore, according to the analytical method of the present invention, it is possible to analyze, for example, a dilute solution of an unstable chemical species that is stable only under acidic conditions and that decomposes or changes in quality when heated, in a simple manner with high accuracy. [Example]

[0053] <Manufacturing of forward osmosis membrane modules> A uniform hollow fiber spinning solution was prepared consisting of 19 mass% polysulfone (Udel-P3500, manufactured by Solvay Specialty polymers), 61 mass% N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 20 mass% tetraethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.). The above-mentioned stock solution was filled into a wet hollow fiber spinning machine equipped with a double spinneret. The stock solution at 40°C and an internal coagulation liquid (water) at 25°C were extruded from the double spinneret. The extruded material was run for 250 mm in air temperature-controlled at 30°C and a relative humidity of 98%, then coagulated in a coagulation bath (external coagulation liquid) filled with 30°C water. The material was then wound up at a tension of 30 g using a free roll as a turn roll to obtain a hollow fiber. The outer diameter of the obtained hollow fiber was 1.02 mm, and the inner diameter was 0.62 mm. This hollow fiber was used as a microporous hollow fiber support layer.

[0054] The microporous hollow fiber support layer was cut to a length of 120 mm, and a hollow fiber bundle of 130 fibers was formed. This hollow fiber bundle was housed in a cylindrical housing 20 mm in diameter and 100 mm in length, and both ends were fixed with an adhesive. Then, both outer ends of the adhesive-fixed parts were cut to open both ends of the hollow fiber bundle, thereby producing a microporous hollow fiber support layer module with an effective length of 80 mm.

[0055] An aqueous solution (first solution) containing 2.0 wt% m-phenylenediamine and 0.15 wt% sodium lauryl sulfate was passed through the hollow fibers of the resulting microporous hollow fiber support layer module for 20 minutes. After passing the solution, the first solution was removed from the module, and while the inner surfaces of the hollow fibers were wet with the first solution, the space outside the hollow fibers of the microporous hollow fiber support layer module was reduced in pressure to 90 kPaG and maintained at this reduced pressure for 1 minute. Air was then passed through the hollow fibers at a linear velocity of 210 cm / sec for 1 minute to remove excess first solution.

[0056] Next, an n-hexane solution (second solution) containing 0.20 wt % of 1,3,5-trimesoyl chloride was passed through the inside of the hollow fibers of the microporous hollow fiber support layer module for 2 minutes to cause interfacial polymerization between the m-phenylenediamine contained in the first solution and the 1,3,5-trimesoyl chloride contained in the second solution, thereby forming a separating active layer made of polyamide on the inside of the hollow fibers.

[0057] Thereafter, nitrogen was passed through the inside of the hollow fibers to remove excess second solution, and hot water at 85°C was passed through the inside of the hollow fibers at a linear speed of 5 cm / sec for 30 minutes. The entire module was then placed in an autoclave (manufactured by Tomy Seiko Co., Ltd., product name "SX-500") and high-temperature steam at 121°C was supplied for 20 minutes. Furthermore, both sides of the hollow fibers were washed with running water at 20°C for 30 minutes to produce a forward osmosis membrane module.

[0058] <<Measurement of salt back-diffusion amount R1 and water permeability F1>> At 25°C, purified water was circulated countercurrently inside the hollow fiber forward osmosis membrane of the forward osmosis membrane module obtained above, and a draw solution consisting of an aqueous sodium chloride solution with a concentration of 3.5 wt % was circulated countercurrently outside the membrane. After 20 minutes, the amount of water (L) (kg) transferred from the purified water to the draw solution and the amount of sodium chloride (G) (g) transferred from the draw solution to the purified water were measured, and the back-diffusion amount of salt (sodium chloride) R1 was calculated using the following formula (1), and the water permeation amount F1 was calculated using formula (2). In formulas (1) and (2), M is the effective surface area (m 2 ) and H is time (h). R1(g / (m 2 ×h))=G(g) / (M(m 2 )×H(h)) (1) F1(kg / (m 2 ×h))=L(kg) / (M(m 2 )×H(h)) (2) As a result, the reverse diffusion amount of salt R1 was 0.29 g / (m 2 × h), and the water permeability F1 is 8.4 kg / (m 2 ×h).

[0059] 《Raw material liquid 1》 The following four reagents manufactured by Perkin Elmer were mixed to prepare an aqueous solution (pH 1.6) containing 100 ppb each of the following 68 elements: Multi-Element Calibration Standard 2: Aqueous solution containing 10 μg / mL each of Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sc, Sm, Tb, Th, Tm, Y, and Yb. Multi-Element Calibration Standard 3: Aqueous solution containing 10 μg / mL of each of the following elements: Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, Ga, In, K, Li, Mg, Mn, Na, Ni, Pb, Rb, Se, Sr, Tl, U, V, and Zn. Multi-Element Calibration Standard 4: Aqueous solution containing 10 μg / mL each of Au, Hf, Ir, Pd, Pt, Rh, Ru, Sb, Sn, and Te. Multi-Element Calibration Standard 5: Aqueous solution containing 10 μg / mL each of B, Ge, Mo, Nb, P, Re, S, Si, Ta, Ti, W, and Zr.

[0060] The aqueous solution (pH 1.6) obtained above was divided into small portions, one of which was kept as is, and ammonia water was added to each of the remaining small portions to prepare aqueous solutions of pH 3.7, 6.0, 8.5, and 9.6. 200 mL of each of these was used as raw material solution 1 (NH3 series raw material solution).

[0061] 《Raw material liquid 2》 An aqueous solution containing 68 elements at 100 ppb each was prepared in the same manner as in the raw material solution 1. Potassium nitrate (KNO3) was added to the obtained aqueous solution to a concentration of 20 mmol / L. The aqueous solution (pH 1.6) after potassium nitrate addition was divided into small portions, and aqueous NaOH solution was added to each portion to prepare aqueous solutions with pH 3.5, 6.5, 7.5, and 10.5. 200 mL of each of the resulting aqueous solutions with pH 3.5, 6.5, 7.5, and 10.5 was used as raw material solution 2 (NaOH-based raw material solution).

[0062] 《Inducing liquid》 As the induction liquid, 200 mL of an aqueous magnesium chloride solution with a concentration of 1 mol / L was used.

[0063] <Forward osmosis concentration operation> Forward osmosis concentration operation was carried out using 200 mL of each pH solution of the NH3 series raw material solution and the NaOH series raw material solution as the raw material solution, and 200 mL of the magnesium chloride aqueous solution as the draw solution. The raw material liquid was stored in a raw material liquid tank, and the draw liquid was stored in a draw liquid tank. The feed solution was supplied to the inside of the hollow fibers of the forward osmosis membrane module, and the draw solution was supplied to the outside of the hollow fibers at a flow rate of 60 mL / min in parallel. After passing through the forward osmosis membrane module, the feed solution and the draw solution were returned to the feed solution tank and the draw solution tank, respectively, and concentration was performed using a circulation system. The weight of the raw material liquid was measured at predetermined time intervals, and the value obtained by dividing the initial weight of the raw material liquid by the measured weight was used as the weight-based concentration factor at that time.

[0064] In addition, 1 mL of the raw material solution was taken at predetermined intervals. For NH3 series raw material liquid, add pure water to dilute 100 times, For NaOH-based raw materials, add 2.0v / v% nitric acid solution and dilute 100 times, The concentrations of 65 elements, excluding B, S, and La, were measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0065] Tables 1-1 to 5-14 show the relationship between the concentration time, the concentration ratio of the weight-based raw material solution, and the concentration and concentration ratio of each element for the NH3 series raw material solution of each pH. In these tables, the number following the element symbol indicates the mass number of the element.

[0066] In addition, for the NH3 series raw solution of each pH, ​​the concentration factor and recovery rate of each element when the concentration factor of the original solution is about 10 times are shown in Tables 6-1 to 6-10. Here, the concentration factor of the original solution is approximately 10 times, which means the following values ​​for each pH. pH1.6:12.4 times pH3.7:9.6 times pH6.0:9.9 times pH8.5:11.4 times pH9.6:10.1 times In Tables 6-1 to 6-10, elements with a recovery rate (element concentration factor / original solution concentration factor) of 70% or higher when the original solution was concentrated about 10 times are marked with a check mark. Furthermore, for the NH3 series raw solution at each pH, ​​the number of elements recovered with a recovery rate of 70% or more when the concentration ratio of the raw solution was approximately 10 times is shown in Table 6-11.

[0067] Similarly, Tables 7-1 to 10-14 show the relationship between the concentration time, the concentration ratio of the weight-based raw material solution, and the concentration and concentration ratio of each element for the NaOH series raw material solution of each pH. In these tables, the number following the element symbol indicates the mass number of the element.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] [Table 4]

[0072] [Table 5]

[0073] [Table 6]

[0074] [Table 7]

[0075] [Table 8]

[0076]

Table 9

[0077]

Table 10

[0078]

Table 11

[0079]

Table 12

[0080]

Table 13

[0081]

Table 14

[0082]

Table 15

[0083] Table 16

[0084] Table 17

[0085]

Table 18

[0086] Table 19

[0087] Table 20

[0088] Table 21

[0089] Table 22

[0090] Table 23

[0091] Table 24

[0092] Table 25

[0093] Table 26

[0094] Table 27

[0095] Table 28

[0096] Table 29

[0097]

Table 30

[0098] Table 31

[0099] Table 32

[0100]

Table 33

[0101] Table 34

[0102] Table 35

[0103] Table 36

[0104] Table 37

[0105] Table 38

[0106] Table 39

[0107] Table 40

[0108] Table 41

[0109] Table 42

[0110] Table 43

[0111] Table 44

[0112] Table 45

[0113] Table 46

[0114] Table 47

[0115] Table 48

[0116] Table 49

[0117] Table 50

[0118] Table 51

[0119] Table 52

[0120] Table 53

[0121] Table 54

[0122] Table 55

[0123] Table 56

[0124] Table 57

[0125] Table 58

[0126] Table 59

[0127] Table 60

[0128] Table 61

[0129] Table 62

[0130] Table 63

[0131] Table 64

[0132] Table 65

[0133] Table 66

[0134] Table 67

[0135] Table 68

[0136] Table 69

[0137] Table 70

[0138] Table 71

[0139] Table 72

[0140] Table 73

[0141] Table 74

[0142] Table 75

[0143] Table 76

[0144] Table 77

[0145] Table 78

[0146] Table 79

[0147] Table 80

[0148] Table 81

[0149] Table 82

[0150] Table 83

[0151] Table 84

[0152] Table 85

[0153] Table 86

[0154] Table 87

[0155] Table 88

[0156] Table 89

[0157] Table 90

[0158]

Table 91

[0159] Table 92

[0160] Table 93

[0161] Table 94

[0162] Table 95

[0163] Table 96

[0164] Table 97

[0165] Table 98

[0166]

Table 99

[0167]

Table 100

[0168] Table 101

[0169] Table 102

[0170] Table 103

[0171] Table 104

[0172] Table 105

[0173] Table 106

[0174] Table 107

[0175] Table 108

[0176] Table 109

[0177] Table 110

[0178] Table 111

[0179] Table 112

[0180] Table 113

[0181] Table 114

[0182] Table 115

[0183] Table 116

[0184] Table 117

[0185] Table 118

[0186] Table 119

[0187] Table 120

[0188] Table 121

[0189] Table 122

[0190] Table 123

[0191] Table 124

[0192] Table 125

[0193] Table 126

[0194] Table 127

[0195] Table 128

[0196] Table 129

[0197] Table 130

[0198] Table 131

[0199] Table 132

[0200] [Table 133]

[0201] [Table 134]

[0202] [Table 135]

[0203] [Table 136]

[0204] [Table 137]

[0205] From the results shown in the table above, it was found that, according to the method of the present invention for the raw solution, even when the concentration by forward osmosis is applied to the raw solution having a pH of less than 3.0, it is possible to concentrate many elements to a high degree with a high recovery rate, and that when the pH of the raw solution is low, there are many more elements with a high recovery rate in the concentration process than when the pH is high. It was verified that high-precision analysis is possible under low pH conditions for raw solutions containing unreliable analytes.

Claims

1. 1. An analytical method for determining the concentration of an analyte in a stock solution comprising the analyte and a solvent, comprising: The analytical method includes a concentration step of concentrating the original solution to obtain a concentrated solution, and a concentration measurement step of measuring the concentration of the analyte in the concentrated solution, the pH of the stock solution is less than 3.0; The concentration step is carried out by a forward osmosis method using a forward osmosis membrane having a separating active layer made of polyamide on the surface of a microporous support layer. Analysis method.

2. 2. The analytical method according to claim 1, wherein the pH of the original solution is 2.5 or less.

3. 2. The analytical method according to claim 1, wherein the microporous support layer of the forward osmosis membrane comprises one or more materials selected from the group consisting of polyethersulfone, polysulfone, polyketone, polyetheretherketone, polyphenylene ether, polyvinylidene fluoride, polyacrylonitrile, polyimine, polyimide, polybenzoxazole, polybenzimidazole, and polyamide.

4. 2. The analytical method according to claim 1, wherein the polyamide constituting the separation active layer of the forward osmosis membrane is a polycondensation product of one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides.

5. 4. The analytical method according to claim 3, wherein the polyamide constituting the separation active layer of the forward osmosis membrane is a polycondensation product of one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides.

6. The forward osmosis membrane has a salt back-diffusion amount R1 of 0.30 g / (m ２ The analytical method according to any one of claims 1 to 5, wherein the total number of saturations is 1.times.h) or less.

7. The forward osmosis membrane has a water permeability F1 of 6.5 kg / (m ２ The analytical method according to any one of claims 1 to 5, wherein the number of the saturation points is 1 × h) or more.

8. The analytical method according to any one of claims 1 to 5, wherein the forward osmosis membrane is a hollow fiber membrane.

9. 6. The analytical method according to claim 1, wherein in the concentration step, the stock solution is placed or passed through the separation active layer side of the forward osmosis membrane, and a draw solution is placed or passed through the microporous support layer side of the forward osmosis membrane.

10. The analytical method according to any one of claims 1 to 5, wherein the analyte in the original solution comprises one or more elements selected from the group consisting of Li, Be, Na, Mg, Al, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Mo, Ru, Rh, Cd, In, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu, Hf, Ir, Pt, Pb, Bi, Th, and U.

11. The analytical method according to any one of claims 1 to 5, wherein the concentration of the analyte in the concentration measuring step is measured by one or more methods selected from the group consisting of chromatography, electromagnetic wave analysis, mass spectrometry, ion analysis, radioactivity analysis, electrochemical analysis, thermal analysis, and X-ray analysis.

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