JP5409213B2 - Cation analysis - Google Patents

Description

The present invention is a method for chromatographically analyzing cations contained in a test solution, and without using an expensive analytical instrument, a dedicated column or a suppressor, alkali metal ions and magnesium ions present in the test solution. The present invention relates to a cation analysis method capable of measuring alkaline earth metal ions with high sensitivity, quickly and easily.

In the separation and analysis method of ions by high performance liquid chromatography (generally called ion chromatography), ion separation, mainly ion exchange resin, is used for ion separation. Traditionally, sulfonated polystyrene gels, which are strong cation exchange resins, have been used for cation separation. Sulfonated polystyrene gel (sulfonic acid type strong cation exchange resin) is an effective separating agent for separation of alkali metal ions, but magnesium ions, alkaline earth metal ions, and transition metal ions coexist. When measuring a test solution, the polyvalent metal ions with high selectivity remain and accumulate in the sulfonic acid type strong cation exchange resin, the apparent ion exchange capacity decreases, and monovalent alkali metal ions There has been a problem that the retention of is extremely reduced.

In order to solve such a problem, a method for producing a carboxylic acid type weak cation exchanger capable of simultaneously separating monovalent alkali metal ions and divalent magnesium ions and calcium ions is disclosed. Non-Patent Document 1 describes a weak cation exchanger in which a polybutadiene / maleic acid film is formed on a silica gel surface using dicumyl peroxide as a catalyst. Valent cations are separated simultaneously. However, detachment (peeling) of the coating polymer is a problem, and as an improvement measure there is a weak cation exchanger obtained by reacting a polybutadiene-maleic acid with a polyvinyl compound such as triallyl isocyanurate in Patent Document 1 as a bridge coating. It is disclosed. Patent Document 2 discloses a method for producing a weak cation exchanger in which a porous substrate is coated with a cured product of a polyfunctional carboxylic acid compound and a polyfunctional epoxy compound. Furthermore, Patent Document 3 and Patent Document 4 disclose a method for producing a weak cation exchange resin in which stability is improved by chemically bonding a polyfunctional carboxylic acid to a polymer base material. Since such carboxylic acid type fillers can simultaneously separate monovalent and divalent cations, they are widely used for water quality analysis of tap water and environmental water. However, even in these fillers, when measuring a test solution containing highly-contained heavy metal ions such as divalent transition metal ions, particularly divalent copper ions and trivalent iron ions, in a high concentration, The problem that these strongly retained metal ions accumulate in the filler and the retention of monovalent alkali metal ions decreases has not been completely solved.

As a method for suppressing the adsorption of heavy metal ions in the test solution to the filler, a heavy cation exchanger similar to that described above is used, and pyridine-2,6-dicarboxylic acid is added to the eluent to thereby remove heavy metal ions. Has been announced to reduce the retention in the filler by complexing to prevent the decrease in retention of monovalent alkali metal ions as well as the improvement of separation (Non-patent Document 2). Although this method is an effective method, there are inconveniences in use such as difficulty in preparation due to low solubility of the reagent, and tendency to mold on the eluent.

The cation exchanger in which heavy metal ions are accumulated can theoretically be regenerated by washing with a strong acid or a chelating agent. For example, in the case of a sulfonic acid type strong cation exchange resin, it can be regenerated by passing 0.5 to 2 M nitric acid through a separation column. The separation column performance can also be recovered by passing a chelating agent solution such as DETA through the separation column. This washing method is basically the same for carboxylic acid type weak cation exchange resins. Furthermore, in order to completely regenerate the ion exchange resin, it is preferable to extract the ion exchange resin from the separation column and wash it with an acid or a chelating agent solution. However, since the commercially available separation column is packed at a high density, it is difficult to exert the same performance as the initial stage even if it is re-packed after extraction and washing. In addition, even when washing is performed by passing the liquid, the packing state may change during the passing of the liquid and the separation column performance may be deteriorated. In general, ion exchange resins are used in a swollen state, but the degree of swelling varies greatly depending on the counter ion and acid / salt concentration. When a sufficiently swollen ion exchange resin is placed in a high-concentration acid / salt solution, it shrinks at once. That is, when a high-concentration acid or salt solution is passed through, the cation exchange resin contracts, and there is a possibility that gaps and channeling occur and the filling state collapses. Therefore, such a reproduction method is not a preferable method.

On the other hand, a conductivity detector is widely used as a method for detecting the separated monovalent and divalent ions. In general, nitric acid, methanesulfonic acid, oxalic acid or the like is used as the eluent. Since these acids have a high molar conductivity, they are detected as negative peaks when the conductivity of the separated monovalent and divalent cations is directly detected. If the polarity of the conductivity detector is reversed, a positive peak is obtained, so that it is easy to calculate the peak area and the like. However, since the background conductivity of the eluent is high, there is a problem that noise is large and low concentration measurement cannot be performed, and temperature fluctuations in the installation environment are likely to occur.

In order to solve such problems, suppressors that reduce background conductivity are commercially available. In the suppressor, the species of the eluent is ion exchanged and converted to water or a low conductivity solution. In cation analysis, the eluent acid is ion exchanged and converted to water. As a result, the background conductivity is reduced, and at the same time, the counter ion of the ion to be measured becomes OH ⁻ type and is sensitized by an increase in molar electrical conductivity. Various suppressors such as a packed column type, a membrane type, an electric regeneration type, an electrodialysis type, and an electrolysis type are commercially available (Non-patent Document 3). Although these suppressors themselves are expensive, in order to use a suppressor, a regenerative liquid feed pump and power supply are required, so if a suppressor is attached to a high-speed liquid chromatograph, high sensitivity measurement is not possible. As a result, expensive ion chromatographs must be used. In addition, when heavy metal ions are contained in the test solution, even if it is not accumulated in the ion exchange group of the filler, the pH increases due to ion exchange in the suppressor and the counter ion becomes OH ⁻ , Some metal ions may precipitate in the suppressor as hydroxides. When such heavy metal precipitation occurs, it is difficult to regenerate the suppressor, and it is necessary to replace an expensive suppressor. In addition, the eluent added with the above-mentioned pyridine-2,6-dicarboxylic acid cannot be applied to the suppressor as described above.

JP-A-5-96184 JP-A-8-257419 JP-A-7-27754 JP-A-11-156216

Chromatography, Vol. 23, no. 7, p. 465-472. Am. Lab. (Fair field Conn.), Vol. 21, no. 5, p. 92-101. Tetsuo Okada, Jun Yamamoto, Yoshinori Inoue, Separation analysis of ionic species by chromatography 4.3.1, p. 91-100, NTS, 2002.

In view of the above-described problems, the present invention provides a separation system in which monovalent and divalent cations in a test solution are less susceptible to reduction in retention of alkali metal ions, performance degradation during regeneration of a packing / separation column, and the like. And a simple and highly sensitive method for analyzing monovalent and divalent cations in combination with an inexpensive and simple suppressor in which the function of the suppressor is unlikely to occur due to coexisting ions.

The present invention relates to a method for chromatographic separation and analysis of cations in a test solution, wherein an eluent containing a boric acid compound and an aromatic diamine compound is passed through a separation column packed with a filler having a hydroxyl group. After separating the cation, the eluate from the separation column is passed through a suppression column filled with an adsorbent that exhibits hydrophobic interaction to reduce the conductivity of the eluent, and then the cation is made to have conductivity. It is detected by a detector.

In the present invention, a filler having a number of hydroxyl groups of 0.5 to 5 meq / g is used as the filler having a large number of hydroxyl groups.

ここで、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４は、水素の置換基としてのＣＨ_３、ＯＨ、ＣＨ_２ＯＨのいずれかであり、ｎは０〜４の整数、ｍは０〜２の整数、ｘおよびｙは０〜２の整数を表す。 In the present invention, the aromatic di-amine compound contained in the eluent is an aromatic diamine compound and its derivative represented by the following formula 1-5.

Here, R ₁ , R ₂ , R ₃ and R ₄ are any one of CH ₃ , OH and CH ₂ OH as a hydrogen substituent, n is an integer of 0 to 4, and m is 0 to 2. Integer, x and y represent an integer of 0-2.

In the present invention, the adsorbent exhibiting hydrophobic interaction packed in the suppression column is an porous porous silica gel in which an alkyl group or an aryl group is introduced or an aromatic vinyl monomer having a ratio of 80 to 100%. A quality copolymer is used.

In the present invention, (1) using a filler having a hydroxyl group without having an ion exchange group, a pseudo ion exchange ability is expressed by complex formation between a boric acid compound in an eluent and a hydroxyl group on the surface of the filler. In order to separate monovalent and divalent cations, accumulation of heavy metal ions in the ion exchange group of the filler is unlikely to occur and can be easily washed. (2) Suppression packed with an adsorbent exhibiting hydrophobic interaction The column has the characteristic of reducing the background conductivity by adsorbing and removing the aromatic diamine used as the eluent, so it can be used as a general-purpose high-speed liquid without using an expensive ion chromatograph, dedicated column, or suppressor. Using a chromatograph, alkali metal ions, magnesium ions, and alkaline earth metal ions can be analyzed easily and inexpensively with a conductivity detector. To become.

FIG. 1 is a diagram showing a system configuration example of a high performance liquid chromatograph for achieving the cation analysis method of the present invention. FIG. 2 is a diagram showing a system configuration example of a high performance liquid chromatograph in which a suppression column regenerative process is incorporated in the cation analysis method of the present invention. FIG. 3 is an example of a chromatogram obtained by separating and separating sodium ions obtained by the cation analysis method of the present invention. FIG. 4 is an example of a monovalent divalent cation chromatogram of tap water measured using the cation analysis method of the present invention.

Hereinafter, the present invention will be described in detail.
In the present invention, for the analysis of cations contained in the test solution, a separation column packed with a filler having a hydroxyl group is used, and as an eluent, an aqueous solution containing a boric acid compound and an aromatic diamine compound is used. The cations in the test solution are separated, and the eluate from the separation column is passed through a suppression column filled with a porous adsorbent that exhibits hydrophobic interaction to reduce the background conductivity of the eluent. The separated cations are detected using a conductivity detector.

As the filler having a hydroxyl group used in the present invention, a commercially available porous hydrophilic filler having a hydroxyl group can be used. However, a vinyl monomer having a hydroxyl group and a crosslinkable vinyl having two or more vinyl groups. It can be produced by copolymerization with a monomer. Examples of the vinyl monomer having a hydroxyl group include vinyl monomers having a hydroxyl group such as 2-hydroxyethyl methacrylate, diethylene glycol methacrylate, 2-hydroxypropyl methacrylate, and 2,3-dihydroxypropane methacrylate. It is preferable to use a diol type vinyl monomer such as 2,3-dihydroxypropane methacrylate which is easy to form. Examples of the crosslinkable vinyl monomer having two or more vinyl groups copolymerizable with the vinyl monomer having a hydroxyl group include ethylene dimethacrylate, diethylene glycol dimethacrylate, glycerin dimethacrylate, trimethylolpropane trimethacrylate, neopentyl glycol trimethyl. Polyfunctional methacrylate vinyl monomers such as methacrylate, ethylene diacrylate, diethylene glycol diacrylate, glycerin diacrylate, trimethylolpropane triacrylate, neopentyl glycol triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, etc. Monomer, other, triallyl isocyanurate, trimethallyl ester Such crosslinkable vinyl monomer having a cyanuric acid structure, such as cyanurate and the like. Aromatic crosslinkable vinyl monomers such as divinylbenzene and divinylnaphthalene can also be used, but the adsorbed amount of the eluent component increases due to the improvement in hydrophobicity. Is preferred. A diol-type filler can also be produced by hydrolyzing the glycidyl group of a copolymer obtained by copolymerization of glycidyl methacrylate and the crosslinkable vinyl monomer. The copolymerization of the vinyl monomer having a hydroxyl group and the crosslinkable vinyl monomer is carried out by a known suspension polymerization method. If necessary, a filler having a hydroxyl group may be added by another polymerization method, for example, a bulk polymerization method. May be obtained.

The filler having a hydroxyl group used in the present invention is preferably a porous body having a large specific surface area in order to obtain high separation ability. In order to obtain a porous filler, at the time of copolymerization, a solvent (pore regulator) that is compatible with these vinyl monomers and does not contribute to the polymerization reaction is added to make the filler porous. The pore regulator is necessary for making the produced polymer porous and increasing the specific surface area, and the pore diameter and the specific surface area are adjusted by the kind and amount of the pore regulator. The pore regulator is appropriately selected depending on the physical properties of the vinyl monomer used, but in general, aromatic hydrocarbons such as toluene and xylene, esters such as butyl acetate and dimethyl phthalate, amyl alcohol, Slightly soluble alcohols such as octyl alcohol and paraffins such as octane and dodecane are used. If the amount of these pore regulators used is too small, sufficient pore diameter and specific surface area cannot be obtained. On the other hand, when the amount of the pore regulator is too large, the degree of swelling becomes soft and the degree of swelling increases, the pore diameter becomes too large and the specific surface area decreases and the mechanical strength decreases. When turbid polymerization is used, there arises a problem that particles are not formed. Therefore, it is used in the range of 30 to 200 parts by weight, preferably 80 to 200 parts by weight, based on 100 parts by weight of the polymerizable vinyl monomer. As the pore diameter and specific surface area of the filler used in the present invention, those having an average pore diameter of 4 to 50 nm and a specific surface area of 100 to 1000 m ² / g are preferably used. Further, the particle diameter is not particularly specified, but usually 3 to 15 μm is used.

The filler having a hydroxyl group produced as described above is used by being packed in a chromatographic tube used in high performance liquid chromatography by a wet packing method. As the material of the chromatographic tube, stainless steel, glass, resin or the like can be used, but it is preferable to use a resin-made chromatographic tube for the purpose of ion analysis. The size of the chromatographic tube is not specified because it is selected depending on the purpose of use and the performance of the separation column, but generally, a tube having an inner diameter of 1 to 8 mm and a length of 50 to 250 mm is used.

The filler having a hydroxyl group produced as described above needs to have a hydroxyl group content of 0.5 to 5 meq / g, and preferably 1 to 5 meq / g. When the amount of hydroxyl groups is less than 0.5 meq / g, it is difficult to adjust the apparent amount of ion-exchange groups produced by complex formation between hydroxyl groups and boric acid compounds, and the cation separation performance is poor, while the amount of hydroxyl groups is less than 5 meq / g. When exceeding, there are problems that the time (equilibration time) until the apparent ion exchange group amount is stabilized becomes long and the peak of the obtained chromatogram becomes broad.

The eluent used in the present invention is an aqueous solution containing a boric acid compound and an aromatic diamine compound. For example, the eluent is prepared by mixing a boric acid compound aqueous solution and an aromatic diamine compound and adjusting the pH with an appropriate acid or alkali. And used. Since the boric acid compound in the eluent forms an anionic complex with the hydroxyl group of the filler under neutral to alkaline conditions, an anionic functional group is imparted to the surface of the filler. As a result, it functions as a pseudo cation exchanger. On the other hand, aromatic diamine compounds act as eluents, and cation separation is achieved by the difference in affinity with the target cation to the pseudo cation exchange group formed by the complex with the boric acid compound on the filler surface. Is done.

Examples of the boric acid compound used in the present invention include boric acid and dihydroxyphenylborane. As the aromatic diamine compound used in the present invention, aromatic diamine compounds represented by the following chemical formulas 1 to 5 are used. Since the cation exchange group formed by the complex formation between the hydroxyl group of the filler and the boric acid compound is a divalent anion, the eluent must also be a divalent ion. The aromatic diamine compound functions as an eluent in the eluent, and also functions as an ion exchange capacity regulator by adsorbing a part of the surface to a filler having a hydroxyl group to impart a cationic property. In addition, in the suppression column of the present invention, the aromatic diamine compound is adsorbed on the adsorbent exhibiting hydrophobic interaction packed in the suppression column, and the background conductivity is reduced. Therefore, it must be a diamine that clearly exhibits hydrophobicity. When the aromatic diamine compound is too hydrophobic, the adsorptivity to the suppression column increases, which is effective in reducing the background conductivity. However, the adsorption amount to the filler having a hydroxyl group as a separating agent is increased, and the cation exchange capacity generated by the complex with the boric acid compound is reduced, which is advantageous for short-time separation of divalent ions. Further, there arises a problem that sufficient retention cannot be obtained for monovalent ions. Therefore, it is necessary to use an aromatic diamine compound having appropriate hydrophobicity, and it is preferable to use m-xylylenediamine in consideration of elution power and solubility in the eluent.

ここで、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４は、水素の置換基としてのＣＨ_３、ＯＨ、ＣＨ_２ＯＨのいずれかであり、ｎは０〜４の整数、ｍは０〜２の整数、ｘおよびｙは０〜２の整数を表す。

Here, R ₁ , R ₂ , R ₃ and R ₄ are any one of CH ₃ , OH and CH ₂ OH as a hydrogen substituent, n is an integer of 0 to 4, and m is 0 to 2. Integer, x and y represent an integer of 0-2.

The concentration of the boric acid compound in the eluent used in the present invention is preferably 0.01 to 1.0% by weight. When the concentration of the boric acid compound is less than 0.01% by weight, complex formation with a hydroxyl group becomes insufficient, the amount of ion exchange groups is difficult to control, and the analysis time tends to be long. On the other hand, when the concentration of the boric acid compound exceeds 1.0% by weight, the background of the conductivity detector increases, and it tends to be difficult to measure a low concentration sample. The concentration of the aromatic diamine compound in the eluent is preferably 0.05 to 1.0% by weight. When the concentration of the aromatic diamine compound is less than 0.05%, the elution ability is insufficient and good separation cannot be obtained. On the other hand, when the concentration of the aromatic diamine compound exceeds 1.0% by weight, the adsorption amount to the filler having a hydroxyl group increases, and an anionic complex is formed with the hydroxyl group of the filler to reduce the ion exchange group. The sample tends to be insufficiently separated. There is also a problem that the suppression column is saturated in a short time. In order to improve the separation, a polar solvent such as methanol or acetonitrile may be added to the eluent.

As a filler for the suppression column used in the present invention, an adsorbent exhibiting hydrophobic interaction is used. As an adsorbent exhibiting a hydrophobic interaction, a copolymer such as silica gel, styrene, divinylbenzene or the like in which an alkyl group or an aryl group is chemically bonded can be used. The particle diameter of these adsorbents is not particularly specified, but usually 3 to 25 μm is used.

As silica gel chemically bonded with an alkyl group or an aryl group, preparations disclosed in JP-A-10-54828, JP-A-2004-117369, JP-A-2004-271522, Table 2006-001300 and the like are prepared. Chemically bonded silica gel prepared by the method can be used. For example, a silanol group on the surface of a silica gel carrier having physical properties of a pore diameter of 6 to 30 μm and a pore volume of 0.8 to 1.2 ml / g, which is generally available, is obtained in a toluene solution containing a silane coupling agent. The alkyl group or the aryl group is substituted by a dehydrochlorination reaction in the presence of pyridine or a non-catalytic dealcoholization reaction. In the present invention, either alkyl group- or aryl group-bonded silica gel can be used, but octadecyl group-bonded silica gel is optimal in consideration of the amount of hydrophobic groups bound and the price of the adsorbent. The introduction amount of the hydrophobic functional group is not strictly defined, but for example, in the case of introducing an octadecyl group, it is preferable to use one having 15% by carbon or more.

The copolymer such as styrene or divinylbenzene can be obtained by copolymerization of an aromatic monovinyl monomer such as styrene or vinylnaphthalene and an aromatic crosslinkable vinyl monomer such as divinylbenzene or divinylnaphthalene. Since the eluent used in the present invention is an aqueous solution, in the case of an adsorbent having high hydrophobicity, the contact property with the eluent may be insufficient. In such a case, an adsorbent obtained by adding a hydrophilic vinyl monomer to the vinyl monomer and copolymerizing it may be used. As a copolymer of an aromatic vinyl monomer and a hydrophilic vinyl monomer, a copolymer of divinylbenzene and vinylpyrrolidone disclosed in publication 2000-514704, disclosed in JP-A-06-258203. A copolymer of divinylbenzene and methacrylate can be used as a reference. The adsorbent used in the present invention is only required to have a clear hydrophobicity, and other than the aromatic adsorbent, a copolymer of vinyl monomers having an alkyl group can also be used. For example, a copolymer of alkyl methacrylate disclosed in JP 2000-9707 A can be mentioned. Moreover, what introduce | transduced the alkyl group into the polyvinyl alcohol-type copolymer disclosed by Unexamined-Japanese-Patent No. 63-225606 can also be referred. However, since it is used to remove the aromatic diamine compound in the eluent, it is preferable to use an adsorbent using an aromatic vinyl monomer that can utilize pp interaction, and the ratio of the aromatic vinyl monomer is It is desirable that it is 80 to 100%.

The adsorbent exhibiting hydrophobic interaction used in the present invention is preferably a porous body having a large specific surface area in order to obtain high separation ability. In order to obtain a porous adsorbent, a solvent (pore modifier) that is compatible with the vinyl monomer and does not contribute to the polymerization reaction is added during copolymerization to make the adsorbent porous. The pore diameter and specific surface area are adjusted depending on the type and amount of the pore regulator, but may be appropriately selected depending on the physical properties of the vinyl monomer used. Generally, aromatic hydrocarbons such as toluene and xylene, esters such as butyl acetate and dimethyl phthalate, sparingly soluble alcohols such as amyl alcohol and octyl alcohol, and paraffins such as octane and dodecane are used. If the amount of these pore regulators used is too small, sufficient pore diameter and specific surface area cannot be obtained. On the other hand, when the amount of the pore regulator is too large, the degree of swelling becomes soft and the degree of swelling increases, the pore diameter becomes too large and the specific surface area decreases and the mechanical strength decreases. When turbid polymerization is used, there arises a problem that particles are not formed. Therefore, it is used in the range of 30 to 200 parts by weight, preferably 80 to 200 parts by weight, based on 100 parts by weight of the polymerizable vinyl monomer. As the pore diameter and specific surface area of the adsorbent used in the present invention, those having an average pore diameter of 4 to 20 nm and a specific surface area of 100 to 1000 m ² / g are preferably used.

The adsorbent produced as described above is used by being packed in a chromatographic tube used in high performance liquid chromatography by a wet packing method. As the material of the chromatographic tube, stainless steel, glass, resin, or the like can be used, but it is preferable to use a resin-made chromatographic tube for the purpose of ion analysis. The size of the chromatographic tube is not specified because it is selected depending on the purpose of use and column performance, but generally, a tube having an inner diameter of 1 to 8 mm and a length of 50 to 250 mm is used. Moreover, since it differs depending on the required analysis time, it cannot be strictly defined, but it is preferable to fill a chromatographic tube having an internal volume of 50% or more of the internal volume of the chromatographic tube used for separation.

The cation analysis method of the present invention is performed using, for example, a chromatograph having a system configuration as shown in FIG. Hereinafter, the operation of the cation analysis method of the present invention will be described with reference to FIG.

An eluent containing a boric acid compound and an aromatic diamine compound is stored in an eluent reservoir 1, conveyed by a liquid feed pump 2, and passed through a separation column 5. At this time, the boric acid compound in the eluent forms an anionic complex with the surface hydroxyl group of the filler having the hydroxyl group packed in the separation column 5. A test solution containing the cation to be measured is accumulated in a desired amount in the sample loop 3b of the injector 3 using the syringe 4 or the like, and is transferred by the eluent by switching the 6-port valve 3a of the injector 3 and separated by the separation column. 5 is injected. The cation to be measured in the test solution separated by the separation column 5 is conveyed to the suppression column 6 by the eluent. At this time, the aromatic diamine compound in the eluent is adsorbed by the adsorbent exhibiting hydrophobic interaction packed in the suppression column 6 and removed from the eluent. By removing the aromatic diamine compound, the ionic component in the eluent is reduced, so that the conductivity is reduced. Furthermore, when the aromatic diamine compound is removed from the eluent, the pH of the eluent is lowered, so that dissociation of the boric acid compound remaining in the eluent is also suppressed, and the background conductivity of the eluent is further reduced. Become. On the other hand, since the counter ion of the separated cation becomes a hydroxide ion, the equivalent electric conductivity is increased. Thus, the measurement target cation conveyed to the separated and suppressed eluent is detected by the conductivity detector 7 and quantified from the detector signal.

Under the separation conditions of the present invention, polyvalent heavy metal ions are difficult to trap, but it cannot be said that there is nothing. Therefore, when a decrease in retention time is observed, the separation column needs to be washed. The ion exchange group of the filler used for separation in the present invention is formed by a complex of the surface hydroxyl group of the filler having a hydroxyl group and a boric acid compound, so that it does not form a complex under acidic conditions, and ion exchange No ability is expressed. That is, by passing an acidic cleaning solution through the separation column, the ion exchange ability is lost, and the solubility of polyvalent heavy metal ions increases under acidic conditions, so that the column can be easily cleaned. Since the packing material of the present invention does not have an ion exchange group, the degree of swelling and shrinkage due to a change in counter ion or salt concentration is low, so that the column performance does not deteriorate. In addition, the filler itself is hydrophilic and hardly adsorbs organic matter, and even if it is adsorbed, it can be easily cleaned by passing a cleaning liquid containing about 10 to 20% of a polar organic solvent. As described above, compared with a separation column packed with a conventional ion exchange resin, washing and regeneration are easy, and there is almost no risk of deterioration in column performance during washing.

In the suppression column, the aromatic diamine compound is removed by hydrophobic adsorption. However, when the adsorbent exhibiting hydrophobic interaction is saturated, the aromatic diamine compound is not removed and the background conductivity is increased. Therefore, it is necessary to stop the temporary measurement and perform the regeneration work before the suppression column is saturated. Regeneration of the suppression column is performed by passing methanol or an acetonitrile aqueous solution to which nitric acid or acetic acid is added. Thereafter, pure water is fed to wash out the cleaning solution remaining in the suppression column, and it is attached to a high performance liquid chromatograph for measurement. However, since the analysis operation is temporarily interrupted by performing such an operation, two suppression columns (6a and 6b) are attached to the 10-port valve 9 as shown in FIG. By performing the above, it is possible to perform the reproduction without interrupting the analysis. At this time, the cleaning / regeneration liquid may be transported from an appropriate liquid feeding system 11. When a plurality of cleaning liquids are required, a plurality of cleaning liquid reservoirs 10 are used, and a switching valve (not shown) is provided on the inlet side of the liquid feeding system 11. May be provided.

EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

Example 1
(Manufacture of separation column A)
(1) Synthesis of filler a having a hydroxyl group The filler having a hydroxyl group was synthesized by a suspension polymerization method. A mixture of 30 g of glycidyl methacrylate, 70 g of ethylene dimethacrylate, 100 g of butyl acetate and 1 g of 2,2′-azobisisobutyronitrile is added to 1500 mL of a 0.1% aqueous polyvinyl alcohol solution, and the center diameter of the oil droplets is obtained using a homogenizer. Was dispersed to be 6 μm. Thereafter, the polymerization reaction was carried out at 70 ° C. for 6 hours with stirring. The produced copolymer particles were collected by filtration and washed with water and methanol in this order. After air drying for one day, classification was performed using an air classifier to obtain 35 g of copolymer particles having an average particle diameter of 6.5 μm. 20 g of the obtained copolymer pair particles were added to a mixed solution of acetonitrile 20 mL and 0.05 M sulfuric acid 80 mL, and reacted at 40 ° C. for 6 hours to hydrolyze the glycidyl group. After hydrolysis, the copolymer particles were collected by filtration, washed with water and methanol, and dried.

(2) Characteristic evaluation of the filler a having a hydroxyl group The specific surface area and the average pore diameter (measured by Beckman Coulter SA3100 Surface Area Analyzer) of the filler a having a hydroxyl group obtained in the above (1) were 232 m ² / g, respectively. And 11.6 nm. The copolymer particles before hydrolysis were dispersed in 0.1 M hydrochloric acid, and the amount of glycidyl group determined from the amount of consumed hydrochloric acid was 2.01 mmol / g. When the glycidyl group of the copolymer particles is hydrolyzed to form a diol, the amount of hydroxyl group is 4.02 mmol / g.

(3) Production of Separation Column A 2 g of the filler a having a hydroxyl group obtained in the above (1) was taken and dispersed in 20 mL of 20% acetonitrile aqueous solution to obtain a uniform slurry. This slurry was put into a packing packer connected with a chromatographic tube having an inner diameter of 4.6 mm and a length of 150 mm, and pure water was fed for 30 minutes using a constant pressure pump set to 15 MPa, and high-pressure slurry was filled.

(Manufacture of suppression column B)
A mixture of 90 g of divinylbenzene (purity: 57%), 10 g of ethylene dimethacrylate, 80 g of toluene, 20 g of lauryl alcohol and 1 g of 2,2′-azobisisobutyronitrile was added to 1000 mL of a 0.1% aqueous polyvinyl alcohol solution. Using a homogenizer, the oil droplets were dispersed so that the center diameter was 15 μm. Thereafter, the polymerization reaction was carried out at 70 ° C. for 6 hours with stirring. The produced copolymer particles were collected by filtration and washed with water and methanol in this order. After air drying for one day, classification was performed using an air classifier to obtain 35 g of copolymer particles having an average particle diameter of 15 μm. The specific surface area and average pore diameter (measured with a Beckman Coulter SA3100 Surface Area Analyzer) of this copolymer were 642 m ² / g and 7.5 nm, respectively. 2 g of this copolymer was taken and dispersed in 20 mL of 40% acetonitrile aqueous solution to make a uniform slurry. This slurry was put into a packing packer connected with a chromatographic tube having an inner diameter of 4.6 mm and a length of 150 mm, and pure water was fed for 30 minutes using a constant pressure pump set at 15 MPa, and high-pressure slurry was filled.

(High sensitivity measurement of sodium ion)
Separation column A packed with filler a having a hydroxyl group and suppression column B exhibiting hydrophobic interaction were mounted on a high-performance liquid chromatogram having the configuration shown in FIG. 1 to separate sodium ions. Table 1 shows the measurement conditions. The chromatogram obtained with and without the suppression column is shown in FIG. As shown in FIG. 3, according to the analysis method of the present invention, the background conductivity was almost 0 μS / cm, and it was completely suppressed and high-sensitivity measurement of sodium ions was possible.

(Example 2)
(Measurement of monovalent and divalent cations in tap water)
Subsequently, the monovalent divalent cation of tap water was measured under the conditions shown in Table 2. As shown in the suppression chromatogram shown in FIG. 4, sodium, potassium and calcium ions could be satisfactorily separated. Also, the measured values showed good agreement with the measured values by the conventional measuring method.

In the present invention, (1) using a filler having a hydroxyl group without having an ion exchange group, a pseudo ion exchange ability is expressed by complex formation between a boric acid compound in an eluent and a hydroxyl group on the surface of the filler. In order to separate monovalent and divalent cations, accumulation of heavy metal ions in the ion exchange group of the filler is unlikely to occur and can be easily washed. (2) Suppression packed with an adsorbent exhibiting hydrophobic interaction The column has a feature of reducing the background conductivity by adsorbing and removing the aromatic diamine used as an eluent. Therefore, without using an expensive ion chromatograph, a dedicated column, or a suppressor, a general-purpose high-performance liquid chromatograph equipped with a conductivity detector can be used for alkali metal ions, magnesium ions, alkaline earth metal on, etc. It becomes possible to analyze a divalent cation easily, inexpensively and stably. Compared to the direct conductivity detection method using nitric acid, methanesulfonic acid, oxalic acid, etc. as the eluent, so-called non-suppressed method, the background conductivity is reduced by the suppression column. There is no problem that measurement is not possible or the temperature of the installation environment is susceptible to fluctuations.

1: Eluent reservoir 2: Liquid feed pump 3: Injector 3a: 6-port valve 3b: Sample loop 3c: Test solution outlet 4: Injection cylinder 5: Separation column 6: Suppression column (same for 6a and 6b)
7: Conductivity detector 8: Waste liquid port 9: 10 port valve 10: Cleaning liquid reservoir 11: Liquid feeding system 12: Cleaning liquid discharge port

Claims (4)

In a method for chromatographic separation and analysis of cations contained in a test solution, an eluent containing a boric acid compound and an aromatic diamine compound is passed through a separation column packed with a filler having a hydroxyl group. After separating the cations, the eluate from the separation column is passed through a suppression column packed with an adsorbent that exhibits hydrophobic interaction to reduce the conductivity of the eluent, and the conductivity of the separated cations is detected. A method for analyzing cations, characterized by detecting with a vacuum vessel. Hydroxyl group content of the filler having a hydroxyl group, a method analyzing cations according to claim 1, characterized in that the 0.5~5meq / g. The aromatic di-amine compound contained in the eluent, the following chemical formula (Formula 1 or Formula 5) aromatic diamine compound represented by any one of and claims 1 or claims, characterized in that a derivative thereof Item 3. The method for analyzing cations according to Item 2.

Here, R ₁ , R ₂ , R ₃ and R ₄ are any one of CH ₃ , OH and CH ₂ OH as a hydrogen substituent, n is an integer of 0 to 4, and m is 0 to 2. Integer, x and y represent an integer of 0-2. An adsorbent exhibiting hydrophobic interaction packed in a suppression column is an porous porous silica gel in which an alkyl group or an aryl group is introduced or an aromatic vinyl monomer ratio of 80 to 100%. The cation analysis method according to claim 1, wherein the cation analysis method is provided.

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