JPH0587787A - Measuring method of negative ions - Google Patents

Abstract

PURPOSE:To obtain a method for measuring simply and correctly negative ions of low-molecular weight contained in a liquid to be measured wherein an electrolyte of high-molecular weight such as protein coexists, without being affected by the electrolyte of high-molecular weight. CONSTITUTION:A pretreatment column 6 which excludes ions of an electrolyte of high-molecular weight in a liquid to be measured and also concentrates negative ions of low-molecular weight selectively is provided between a first selector valve 4 collecting the liquid to be measured in a prescribed quantity and a separation column 7 separating chromatographically the negative ions of low-molecular weight in the liquid to be measured. The electrolyte of high- molecular weight in the liquid is removed in the pretreatment column 6, only the negative ions of low-molecular weight are led to the separation column 7 and separated therein chromatographically, and thereafter the negative ions of low-molecular weight are detected by a detector 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring anions, and more particularly, to a method for measuring a high molecular weight electrolyte containing low molecular weight anions contained in a solution to be measured in which a high molecular weight electrolyte such as a protein coexists. The present invention relates to a simple and accurate measurement method without being affected by.

[0002]

2. Description of the Related Art High performance liquid chromatography or ion chromatography is often used to measure anions in a liquid to be measured. However, when a high molecular weight electrolyte such as a protein other than the measurement component coexists in the liquid to be measured, low molecular weight anions such as inorganic anions contained in the liquid to be measured are separated and analyzed using an anion exchange resin. At that time, there were the following problems.

That is, first, proteins and the like in the solution to be measured are adsorbed on the surface of the ion exchange group or the ion exchange resin, and the apparent ion exchange capacity is reduced. For this reason, the separation ability of the anions in the separation column is lowered, and as a result, the quantification ability of the anions is often lowered. Secondly, when the ion-exchange groups and proteins adsorbed on the surface of the ion-exchange resin accumulate, the pressure resistance of the column increases, and the regeneration of the column becomes extremely difficult.

In order to deal with such a problem, a method of deproteinizing the liquid to be measured in advance, a method of frequently washing the separation column to remove the adsorbed protein, and a precolumn for adsorbing the protein are installed in front of the separation column. The method of removing the protein by the method was tried. But the method of
The pretreatment of the sample takes time and the deproteinizing agent may adversely affect the separation of the ions to be measured. Further, there is also a drawback that the ions to be measured are incorporated into the protein that is removed by precipitation or the like.

The method (1) has a drawback in that the analysis must be stopped once and a solvent different from the eluent must be passed through the separation column, which is not preferable in terms of maintaining continuity of the analysis and maintenance. In addition, since the protein once adsorbed cannot be easily washed away, the separation column is consumed quickly. The method (1) has a drawback that the apparatus becomes complicated and the adsorption column needs to be maintained.

On the other hand, as a method for solving the above-mentioned problems all at once, it has been attempted to measure a low molecular weight anion in a liquid to be measured using the following anion exchange resin. That is, when a solution to be measured in which a high molecular weight electrolyte such as a protein coexists is introduced, only the anions of low molecular weight materials are selectively ion-exchanged and the low molecular weight anions are chromatographically separated without being affected by proteins and the like. An anion exchange resin has been developed, and it has been attempted to measure low molecular weight anions in a liquid to be measured.

[0007]

However, when this method is applied to suppressed ion-chromatography, the protein eluted from the anion exchange resin as described above is adsorbed on the cation exchange membrane of the suppressor to suppress the performance of the suppressor. There was a serious drawback that it decreased in a short time. Therefore, the method for measuring low molecular weight anions in the liquid to be measured using the anion exchange resin can be used only for non-suppressed ion chromatography.

On the other hand, it has been widely known that the measurement sensitivity of anions measured by non-suppressed ion chromatography is significantly inferior to that measured by suppressed ion chromatography.
In particular, when the anion concentration in the measured liquid became lower than several ppb, the anion in the measured liquid could not be measured with high precision unless it was a suppressed-type ion chromatography combined with the concentration column method. Also, in the case of non-suppressed ion chromatography, if an ultraviolet detector or an electrochemical detector is used as a detector, these detectors are contaminated with proteins and the like eluted from the separation column filled with the anion exchange resin, and the detector is detected. There was a drawback that the performance of the.

The present invention has been made in view of the drawbacks of the conventional example, and its object is to increase the amount of low molecular weight anions contained in a solution to be measured in which a high molecular weight electrolyte such as a protein coexists. An object of the present invention is to provide a method for easily and accurately measuring without being influenced by a molecular weight electrolyte.

[0010]

The present invention relates to a method for measuring anions contained in a liquid to be measured by high performance liquid chromatography or ion chromatography, and a first switching valve for collecting a fixed amount of the liquid to be measured and said first switching valve. A pretreatment column is provided between the separation column that chromatographically separates low-molecular-weight anions in the measurement liquid, to exclude high-molecular-weight electrolytes in the measurement liquid and to selectively concentrate low-molecular-weight anions. , The pretreatment column removes the high molecular weight electrolyte in the solution to be measured and guides only the low molecular weight anions to the separation column for chromatographic separation, and thereafter,
The above problem is solved by detecting the low molecular weight anions with a detector.

[0011]

The present invention operates as follows. That is, when the sample loop is filled with the liquid to be measured and then the first switching valve is turned on, the liquid to be measured in the sample loop is transported to the sample carrier liquid to reach the pretreatment column, and High molecular weight electrolytes such as proteins contained in the measurement liquid are ion-excluded and discharged, and only low molecular weight anions contained in the measurement liquid are selectively concentrated.

After that, when the second switching valve is turned on, the low molecular weight anions that have been concentrated and retained in the pretreatment column are conveyed to the eluent and reach the separation column where they are chromatographically separated. The eluate of the separation column passes through the inner chamber of the suppressor to reduce the conductivity background, and then is detected by the detector to qualitatively or quantitatively analyze the low molecular weight anions contained in the liquid to be measured. Be seen.

[0013]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, in which 1a is a sample carrier liquid tank in which a sample carrier liquid is stored,
b is an eluent tank in which an eluent composed of an aqueous solution containing 4 mM sodium carbonate and 4 mM sodium hydrogen carbonate is stored, and 1c is a removal liquid tank in which a removal solution composed of a 15 mM sulfuric acid aqueous solution is stored. 2a to 2c are liquid feed pumps, 3 are anion trap columns, 4 are first to sixth
Is a first switching valve having connection ports 4a to 4f and a sample loop 4g.

Further, 5 is the first to sixth connection ports 5a to 5f.
And a second switching valve having a pretreatment column 6 described later, 6 is a pretreatment column filled with an anion exchange resin capable of selectively exchanging low molecular weight anions, and 7 is, for example, a completely porous polystyrene gel A separation column comprising a low ion-exchange capacity anion-exchange resin in which trimethylammonium-type anion-exchange latex is fixed on the surface of
A suppressor 8 is an ion exchange membrane 8a whose interior is divided into an inner chamber 8b and an outer chamber 8c, and 9 is a detector such as a conductivity meter.

In one embodiment of the present invention having such a structure, first, the first and second switching valves 4 and 5 are off, and all the internal flow paths are in the solid line connection state of FIG. ..
In this state, when the liquid feed pump 2a is driven, the sample carrier liquid in the tank 1a becomes liquid feed pump 2a → anion trap column 3 → first and second connection ports 4a, 4b of the first switching valve 4 → second
Flows through the fourth and third connection ports 5d and 5c of the switching valve 5 → the pretreatment column 6 → the sixth and fifth connection ports 5f and 5e of the second switching valve. Here, in the sample carrier liquid, anions other than the low molecular weight anions contained in the liquid to be measured are pretreated in the column 6
In order to prevent it from being concentrated in advance, the anions contained when passing through the anion trap column 3 are removed.

When the liquid feed pump 2c is driven, the tank 1c
The removal liquid inside flows through the liquid feed pump 2c → the outer chamber 8c of the shade suppressor 8, and when the liquid feed pump 2b is driven, the tank 1
The eluent in b flows through the liquid feed pump 2b → the first and second connection ports 5a and 5b of the second switching valve 5 → the separation column 7 → the inner chamber 8b of the suppressor 8 → the detector 9.

In this state, the liquid to be measured, which is, for example, serum, is injected from the fifth connection port 4e of the first switching valve 4 to fill the inside of the sample loop 4g. Next, when the first switching valve 4 is turned on and the internal flow path is switched from the solid line connection state to the broken line connection state, the measured liquid in the sample loop 4g is transported to the eluent and the pretreatment column 6 And the high molecular weight electrolytes such as proteins contained in the liquid to be measured are eliminated by the second ionization.
Only the low molecular weight anions contained in the liquid to be measured are selectively concentrated while being discharged via the sixth and fifth connection ports 5f and 5e of the switching valve 5.

After that, when the second switching valve 5 is turned on and the internal flow path is switched from the solid line connection state to the broken line connection state, the low molecular weight in the liquid to be measured concentrated and retained in the pretreatment column 6 is reached. The anions are transported to the eluent, reach the separation column 7, and are chromatographically separated. The eluate of the separation column 7 passes through the inner chamber 8a of the suppressor 8 to reduce the conductivity background, and then the detector 9
Detected in. The detection signal is guided to a recorder (not shown) to draw a chromatogram, and the low molecular weight anions contained in the liquid to be measured are qualitatively or quantitatively determined based on the chromatogram or the like.

The present invention is not limited to the embodiment shown in FIG. 1, and various modifications are possible. For example, the suppressor 8,
The removal liquid tank 1c and the liquid feed pump 2c may be removed and the eluate of the separation column 7 may be directly guided to the detector 9. Further, the detector 9 may be an ultraviolet absorption detector or an electrochemical detector other than the conductivity detector.

[0020]

According to the present invention as described in detail above, the high molecular weight electrolyte such as protein contained in the solution to be measured is eliminated by the pretreatment column and discharged to the outside of the measurement system. It is in a clean state when the liquid is injected. Therefore, there is an advantage that the pretreatment column does not need to be maintained for each measurement.

Further, since the impurity ions contained in the sample carrier liquid can be removed by the anion trap column, there is also an advantage that an extremely small amount of anions contained in the liquid to be measured can be measured with high accuracy. If the switching of the switching valve is driven by a time program using a sequencer, there is also an advantage that the measurement can be automatically performed after the injection of the liquid to be measured.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an embodiment of the present invention.

[Explanation of symbols]

 1a Sample carrier liquid tank 1b Eluent tank 1c Removal liquid tank 2a to 2c Liquid transfer pump 3 Anion trap column 4, 5 Switching valve 6 Pretreatment column 7 Separation column 8 Suppressor 9 Detector

Claims (3)

[Claims] 1. A method for measuring anions contained in a solution to be measured by high performance liquid chromatography or ion chromatography, wherein a first switching valve for collecting a fixed amount of the solution to be measured and a low molecular weight anion in the solution to be measured. Between the separation columns for chromatographically separating the ions, a pretreatment column for eliminating the high molecular weight electrolytes in the liquid to be measured and concentrating selectively the low molecular weight anions is provided, and the pretreatment column is used. It is characterized in that the high-molecular weight electrolyte in the liquid to be measured is removed and only low-molecular weight anions are guided to the separation column for chromatographic separation, and then the low-molecular weight anions are detected by a detector. Method for measuring anions. 2. The measuring method according to claim 1, wherein the detector is a conductivity detector, an ultraviolet absorption detector, or an electrochemical detector. 3. The measuring method according to claim 1, wherein the separation column is a packed column for ion exchange chromatography packed with an anion exchange resin having a low ion exchange capacity.