JPS63247654A - Analysis of anion - Google Patents

Abstract

PURPOSE:To pass a sample of a certain concn. range continuously in a sepn. column and to permit quantitative analysis of anion by passing a liquid mixture composed of an eluant and the anion to be detected continuously to the sepn. column, supplying the specified amt. of an alkaline soln. to the sepn. column and measuring the liquid flowing out of the sepn. column with an electrical conductivity detector. CONSTITUTION:The eluant 1 and the sample 2 contg. the anion to be measured are controlled in flow rate by solenoid valves 3, 3' operating at a high speed and are mixed at a specified ratio in a confluent part 20. The mixture is sent through an injector part 5 by a pump 4 to the sepn. column 6. A specified amt. of the alkaline soln. is injected from the injector 5 by a microsyringe 7. A conductivity cell 9 is used for the detector 8 and the data monitored in the cell 9 is recorded as retention time, peak height and peak area by a data processor 11. The quantitative analysis of the anion is permitted while the sample of the certain concn. range is continuously passed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anion analysis method, and particularly to an anion analysis method applying liquid chromatography.

[Conventional technology]

In liquid chromatography, a separation column is generally filled with an ion exchange resin or an adsorbent packing material, and an eluent is supplied to the column to separate the components of an injected sample. As the speed of liquid chromatography has increased, the amount of eluent fed has decreased, and the capacity of separation columns has also become smaller. Along with this, the volume of sample introduced has also been reduced.

On the other hand, the following prior art has been announced in the field of ion chromatography, regardless of the reduction in sample volume as described above. This prior art is published in "Analytical Chemistry, Vol. 56, pp. 2073-2078 (1984).
(Anal, Chew,, vol.

56, pp. 2073-2078 (1984)) in ion chromatography.
It has been suggested that if only the eluent is allowed to flow continuously through the separation column and distilled water is injected into the flow, anions in the eluent can be detected as absent peaks.

[Problem that the invention seeks to solve]

In conventional liquid chromatography, a small, fixed amount of sample is injected into a stream of eluent and its components are separated by a separation column. As the flow rate of eluent is reduced by micro liquid chromatography, the amount of sample to be injected must become extremely small, and it becomes extremely difficult to measure and inject such a very small amount of sample. . For example, if the eluent flow rate is several μ
If the sample amount were to be reduced to Q/min, the sample amount would have to be on the order of nfl, but it is practically difficult to accurately measure such a minute amount.

On the other hand, the above-mentioned prior art does not suggest any method for utilizing the phenomenon in which an absent peak appears for quantitative analysis.

The purpose of the present invention is that even if a small capacity separation column is used,
An object of the present invention is to provide an anion analysis method capable of quantitatively analyzing anions in a sample using liquid chromatography.

Means for Solving Problem C] The present invention consists of continuously flowing a mixture of an eluent and a sample containing a test anion through a separation column, the mixture being acidic or neutral, The present invention is characterized in that a certain amount of an alkaline solution that does not substantially contain the test anion is supplied to the separation column, and the liquid flowing out from the separation column is measured with a conductivity detector.

The alkaline solution is preferably, for example, a potassium hydroxide solution or a sodium hydroxide solution, which is added in pulses to the separation column or to the mixed liquid stream.

[Effect]

When a sample solution is continuously flowed through a separation column in advance, the analyte component reaches an adsorption/desorption equilibrium between the column filler and the solution within the separation column. Here, the column packing material is an anion exchange resin with a low exchange capacity, and the analyte component is an anion. Ion exchange equilibrium is therefore achieved within the column.

When 8 liquids of alkali hydroxide are added in a certain amount (small amount), the hydroxide ions drive out the target anions that have already been adsorbed, and the hydroxide ions are abundant on the ion exchange resin and the target anions are absorbed. A deficient band is formed. This is developed by the anion of interest and other solutes in the sample and elutes from the separation column at a position corresponding to the elution position of each anion of interest in the sample. The eluted hydroxyl ions combine with hydrogen ions to form water, resulting in a chromatogram that lacks each target anion.

Since the amount of the target anion adsorbed in advance is proportional to the concentration in the sample solution within a certain concentration range, it is also quantitative.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a flow path diagram of a chromatographic apparatus for carrying out the present invention. The eluent 1 and the sample 2 are mixed at a constant ratio in the confluence section 20 with their flow rates adjusted by electromagnetic valves 3 and 3' operating at high speed, and are sent to the separation column 6 via the injector section 5 by the pump 4. A fixed amount of alkaline liquid is injected from the injector 5 using the microsyringe 7. A conductivity monitor having a cell 9 was used as the detector 8, and the 'R4R4 cell 9 was placed in a column oven 10 together with the separation column 6 and kept at a constant temperature of 40°C.

A data processing bag @11 was connected to the conductivity monitor 8, and the retention time, peak height, peak area, etc. were recorded.

As the separation column, one filled with a small-capacity packing material such as one for adsorption/one distribution or ion exchange is used. For example, when a packing material with an exchange capacity of 3 μeq/g is used, the time from the start of introduction of the mixture of eluent and sample into the separation column to equilibration within the separation column is about 20 minutes. If equilibration is to be achieved within 3 hours, it is necessary to use a filler with a capacity of 30 μeq/g or less.

A mixture of eluent and sample is continuously passed through a small-capacity separation column for adsorption/distribution or ion exchange.
Achieve equilibration such as partitioning or ion exchange. Next, when a certain amount of separation solvent is sent to the separation column, the analyte component, which was in equilibrium due to adsorption to the packing material under the previous conditions, will maintain an equilibrium state with the separation solvent. behave.

As a result, the analyte components that were retained in the separation column by adsorption etc. will be extracted into the separation solvent.
It is discharged as the separation solvent is discharged from the separation column. Within the separation column, the separation solvent is transferred while being sandwiched between the eluent and sample mixture.

As the mixture of eluent and sample that is continuously supplied into the separation column advances through the separation column, the amount of analyte in the sample is removed to compensate for the part of the analyte that was removed as the separation solvent passed through the column. The analyte is depleted, and the band lacking the analyte is moved and developed within the separation column in the same manner as in normal operation.

The amount of dissociation solvent injected into the eluent-sample mixture stream must be accurately metered.

For injection, an automatic introduction device with a metering tube attached to a flow path switching valve is usually used, but an injection device such as a syringe needle may also be used. The injection amount of the separation solvent is selected depending on the type of filler, the flow rate of the eluent, the concentration of components in the sample, the detection sensitivity of the detector, etc. Practically, the capacity that can be accurately measured is set using a measuring tube, etc., and is usually 1 μQ to 1 m.
Q is often used.

In the eluent tank 1, potassium hydrogen phthalate (p
H4,3) is accommodated. The liquid pump 4 is a reciprocating type double screw I-type pump.

Usually the flow rate is less than 1 mQ/min, especially μQ/mi.
The operation is controlled by a controller so as to send a microscopic amount of liquid on the order of n.

Separation column 6 is a Hitachi backed column Nα2710S.
A-I C was used, but the size was 4 + nm in inner diameter,
The length is 50 nm. Column 6 was filled with Hitachi custom ion exchange resin 271O8-IC.

The filler is an anion exchange resin with a low exchange capacity, approximately 20 μeρ/g. As a filler,
Ion exchange resin with even smaller ion exchange capacity, μ
It is possible to apply adsorbents with adsorption capacities on the order of m o Q / g.

The chromatogram shown in FIG. 2 shows an experimental example using the apparatus shown in FIG. Sample 2 was F-, (12-) at a concentration of 4.0 ppm using 1.5 mM potassium hydrogen phthalate (pH 4.3) as the eluent.

Aqueous solutions containing Not-, Br-, N0a-, and SO4'' were used. These solenoid valves 3 and 3'
The output of the conductivity monitor 8 was monitored when 250 μQ of pure water (dotted line) or 1 μQ of a solution containing 1100 pp of each of the above ions was injected from the injector 5 (solid line). It is.

Here we see a decrease in conductivity upwards.

That is, the solid line indicates a normal ion chromatogram.
The dotted line indicates a "vacant chromatogram" lacking the target ion.

In Fig. 2, the peak of the broken line is F″″21°CQ-
22, No2-23. B r″″24. This is the paycant anion peak of No. 3-25°5O42-26.

In the vacant chromatogram, peaks lacking components appear at positions that should be eluted in ion chromatography, and when pure water is added, the peaks after NOs- and before and after the peaks of SO42- are disturbed. I understand that. Note that a pecant peak of phthalate ions appears at 16 minutes.

Figures 3 to 6 show the state of paycant chromatograms when various injection solutions were used, and the concentration of each anion in the sample was 4.0 ppm, the same as in Figure 2.
It is. In FIGS. 3 to 6, predetermined amounts of various liquids were injected from the injector section 5 of the apparatus shown in FIG. That is,
In Figure 3, 25 μQ of 1mM potassium hydroxide was added, and in Figure 4, 0.75mM potassium hydrogen phthalate (pH 4,3) 2
A paycant chromatogram was obtained by injecting 5μ12 of pure water, 250μQ of pure water in FIG. 5, and 25μQ of pure water in FIG. As shown in FIG. 3, when 1 mM potassium hydroxide was added, a good chromatogram with no baseline disturbance was drawn. Furthermore, when comparing the chromatogram (Fig. 6) with 25 μQ of pure water added, the sensitivity was about 3 times higher.

Figure 7 shows that the concentration of sample solution 2 was varied from 1 to 10 ppm.
This is a calibration curve obtained by injecting 25μα of 1mM potassium hydroxide. Although the calibration curve obtained by injecting 250 μQ of pure water had almost no range showing linearity, it was found that adding potassium hydroxide showed good linearity within a certain concentration range.

The liquid to be injected only needs to be an alkaline solution that dissociates to produce hydroxide ions, such as lithium hydroxide.

Practical examples include sodium, potassium, and ammonium.

〔Effect of the invention〕

According to the present invention, a "vacant chromatogram" without baseline disturbance can be drawn.

Quantitative analysis of anions is possible by continuously flowing a sample in a certain concentration range.

Another side effect is that detection can be performed with higher sensitivity than when injecting pure water or the like.

[Brief explanation of the drawing]

Figure 1 is a flow path diagram of the chromatography device used to carry out the present invention, Figure 2 is a diagram comparing ion chromatograms and paycant chromatograms, and Figures 3 to 6 are various injection solutions. FIG. 7 is a diagram showing examples of calibration curves for various anions to which the present invention is applied. DESCRIPTION OF SYMBOLS 1... Eluent, 2... Sample liquid, 5... Injector, 6... Separation column, 9... Electricity cell. Figure 2 lI now βJ + ('7F no

Claims (1)

[Claims] 1. Continuously flow a mixture of the eluent and the sample containing the test anions through the separation column; the above mixture must be acidic or neutral; and the mixture must be alkaline, which does not substantially contain the test anions. supplying a certain amount of solution to the separation column;
An anion analysis method comprising measuring the liquid flowing out from the separation column with a conductivity detector.