JPH076960B2 - Ion chromatograph - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ion chromatograph, and more particularly to an ion chromatograph suitable for liquid chromatographic analysis of both cation and anion ion species. .

[Conventional technology]

Application of ion chromatography has been performed to analyze both cations and anions contained in liquid mixture samples. For example, “Analytical Chemistry, Volume 54 (1982) pp. 462-469 (Ana
L. Chem., col54 (1982) pp462-469) ", a cation exchange column and a cation exchange column were connected in series, a single eluent was passed through both columns, and the cation exchange column was passed through both columns. It has been shown to detect ions and anions with a detector.

[Problems to be solved by the invention]

In the above-mentioned conventional technology. Both columns have a constant flow rate of a single eluent. However, according to such a method, the anion component and the cation component interfere with each other in detection, which makes it difficult to perform highly accurate separation analysis.

An object of the present invention is to eliminate the overlap between the peak of the cation component and the peak of the anion component when analyzing both cation and anion ion species with the same analyzer, and to analyze both ion components with high precision. An object is to provide an ion chromatograph device.

[Means for solving problems]

In the present invention, the first and second components capable of separating different ionic species are separated.
In an ion chromatograph for detecting cations and anions passing through both columns by arranging the ion exchange columns in series, and eluting outflow from the first column between the first column and the second column. It is characterized in that a change liquid for changing the composition or flow rate of the liquid is introduced.

[Action]

In the present invention, the combination of the first column and the second column is, for example, the combination of the anion exchange column and the cation exchange column. Either column may be on the upstream side.

The conventional overlap between the anion peak and the cation peak is due to the fact that the liquid flowing through the first column and the liquid flowing through the second column have the same composition and flow rate. In the present invention, the first
The changing liquid is supplied to the second column arranged on the downstream side so as to change the composition or the flow rate of the liquid flowing through the column and the liquid flowing through the second column. As a result, the elution condition of the specific ion species passing through the second column is changed, so that the elution time (retention time) of the ion component can be changed.

As an example of changing the flow rate of the liquid passing through the second column, a pump for sending the changing liquid to the second column may be provided in addition to the pump for sending the eluting liquid to the second column. These pumps
Preferably, it is controlled by the controller so as to change the flow rate with the lapse of time, whereby the analysis time of the test sample can be shortened. When changing the composition of the liquid passing through the second column, a changing liquid having a different composition from the composition of the eluent supplied to the first column is supplied to the second column. The composition change includes the concentration change. When you want to elute the target ion component quickly, combine the change solution with a higher concentration than the eluent concentration into the eluent between the first and second columns to elute the target component later. If desired, a change solution having a concentration lower than the eluent concentration is combined with the eluent.

〔Example〕

FIG. 1 shows a schematic configuration diagram of an embodiment of the present invention. In this embodiment, a column filled with an anion exchange resin is used as the first column 4a on the upstream side, and a column filled with a cation exchange resin is used as the second column 4b on the downstream side. The present invention can be applied even if the arrangement is reversed, but the separation accuracy between components is superior in this embodiment.

In this example, the eluent 1a and the modification liquid 1b as the second eluent had the same composition, and a 2 mM benzoic acid solution was used. The flow rate of the eluent in the first column 4a is determined by the discharge amount of the liquid feed pump 2a, and the flow rate of the liquid flowing in the second column 4b is determined by the total amount of the discharge amounts of both the liquid feed pump 2a and the liquid feed pump 2b. It The merging portion 5 is formed of, for example, a Y-shaped tube, and both liquids are mixed by merging.

The eluent 1a is supplied by the pump 2a at a constant flow rate to the sample introduction device
Sent to. A predetermined amount of the mixture sample is injected into the eluent by the sample introduction device 3, and the anions in the sample are separated by the anion exchange column 4a. On the other hand, the changing liquid 1b sent from the pump 2b merges with the eluent 1a in the mixing section 5 and is sent to the cation exchange column 4b. Column 4a for cations in the sample
Are eliminated by passing through the column, separated by the column 4b, and then detected by the detector 6. Further, the anions separated in the column 4a are eliminated by the column 4b, pass through, and are detected by the detector 6, and the response signals of both detected ion species are recorded by the recorder 8. The flow rate controller 7 controls the flow rates of the pumps 2a and 2b. The detector 6 is an electric conductivity detector, but an absorptiometer can be applied if necessary.

Next, the results of experiments to which the present invention is applied will be described. Second
FIG. A shows a chromatogram when the present invention is not applied, and FIG. 2B shows a chromatogram when the present invention is applied. In each case, the apparatus shown in FIG. 1 was used, and 2 mM benzoic acid was used as the eluent 1a and the change solution 1b.

In Fig. 2A, the pump 2b is stopped and only the pump 2a is operated, and the eluent of 1.0 ml / mi is applied to both columns by the pump 2a.
Flowed at a flow rate of n. As a sample, lithium chloride (LiC
l), sodium bromide (NaBr), ammonium chloride (NH ₄
A solution containing Cl) and potassium nitrate (KNO ₃ ) was used. When the detector is an electric conductivity detector, cations are detected as minus peaks (deps) from the baseline and anions are detected as plus peaks.

In FIG. 2A, peak 13 is called a bacant dep and is caused by the injection of the sample. Since the Li ₊ peak 9 and the Na ₊ peak 10 overlap with the Vacant dep 13 and the NH _{4 +} peak 11 and the K ₊ peak 12 overlap with the Cl ⁻ peak 14, it is difficult to accurately quantify these ionic components. Br ⁻ peak 15 and NO ₃ ⁻ peak 16 are undisturbed.

The chromatogram in Figure 2B shows that the flow rate of pump 2a is 0.5 ml /
It was obtained by merging the eluent 1a and the change liquid 1b at the merging portion 5 while keeping the min constant and the flow rate of the pump 2b at 1.0 ml / min. The sample is the same as in FIG. 2A. In this case, the flow rate of the eluent through the first column 4a is because smaller than in the case of Figure 2 ^{A, Cl - 14, Br -} 15, NO 3 - Any anions such as 16 retentivity Chillon time increases. On the other hand, Li
Cations such as ₊ 9, Na ₊ 10, NH ₄₊ 11, K ₊ 12 are _detected in the second column 4b.
Since the combined flow rate of the eluent and the change liquid passing through is larger than that in the case of FIG. 2A, the retention time tends to be small. In FIG. 2B, all the cation depletions were previously eluted from the Baikant dep 13 and separated from the anion peak eluting after the Baicand dep 13.

The applied flow rate relationship in Figure 2 B last NO ₃ ^- takes about 44 minutes to elute the peak 16, not slow practical. In order to accelerate the elution of the anionic species, the combined flow rate of the liquids passing through the second column 4b is constant, but the flow rates of the eluent 1a passing through the first column 4a are increased so that the flow rates of the eluents 1a increase with time. Was controlled by a flow controller 7 equipped with a microcomputer.

That is, while the total time is 30 minutes, the flow rate of the pump 2b is linearly reduced from 1.0 ml / min to 0 ml / min, and the flow rate of the pump 2a is linearly reduced from 0.5 ml / min to 1.5 ml / min. I increased it to. The chromatograph of FIG. 3 was obtained in this way for the same sample. Baseline varies somewhat, but the last NO ₃ ^- elution time of the peak 16
The analysis time can be shortened to 25 minutes and the analysis time can be shortened by 19 minutes as compared with FIG. 2B.

Although the flow rate was changed linearly in FIG. 3, the second column 4b
The analysis time can be shortened even if the eluent flow rate through the first column 4a is increased stepwise while keeping the total flow rate through the column constant.

In the above analysis example, the eluents 1a and 1b were the same 2.0 mM benzoic acid solution, but different composition liquids can be combined. However, when using a conductivity detector, it is desirable that the electric conductivity of both eluents be equal at the confluence 5. Otherwise, pulsating flow noise of the pump appears and the detection sensitivity is lowered. Also, when an absorptiometer is used as a detector, it is necessary to reduce the pump pulsating flow noise by selecting the concentration or the detection wavelength so that the absorbances of both eluates are equal.

In the above analysis example, 4a was used as an anion exchange column and 4b was used as a cation exchange column, but it is also possible to reverse the order of the anions and cations to be eluted by the reverse combination.

〔The invention's effect〕

According to the present invention, since the measurement can be performed so as to prevent the overlap between the anion peak and the cation peak, the quantification accuracy of both ion species can be significantly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention, FIG. 2A is a diagram showing a chromatogram when the present invention is not applied, and FIGS. 2B and 3 are cases where the present invention is applied. It is a figure which shows a chromatogram. 1a ... Eluent, 1b ... Change solution, 2a, 2b ... Pump, 4a ...
… First column, 4b …… Second column, 5 …… Confluence section, 6 ・ ・ ・
…Detector.

Claims (2)

[Claims] 1. A first and second device capable of separating different ionic species into components.
In an ion chromatograph for detecting cations and anions passing through both columns by arranging the ion exchange columns in series, and eluting outflow from the first column between the first column and the second column. An ion chromatograph device, characterized in that a change liquid for changing the composition or flow rate of the liquid is introduced. 2. The apparatus according to claim 1, wherein the changing liquid has the first conductivity or the first absorption.
An ion chromatograph, which is substantially the same as the eluent flowing out from the column.