JPH02208559A - Analysis of organic acid - Google Patents

Abstract

PURPOSE:To achieve a higher analysis work efficiency by detecting organic acid as conductivity of ions while a signal of a non-ionic coexisting substance is not detected to eliminate a pretreatment removing work of non-ionic substance with excellent selectivity. CONSTITUTION:An eluate 1, a pump 2, an injector 3, a column 4, a chromatographic data processor 5, a conductivity detector 6 and a column thermostatic cell 7 are arranged in this method. In analysis, a density of the eluate is lowered from 3 millimole down to 1, 0.5 and 0.3 millimole to reduce a stability (background) of a base line. Moreover, this achieves a higher determination accuracy with the capability of separation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to liquid chromatography, and particularly to an analytical method suitable for analyzing organic acids.

[Conventional technology]

The conventional device, as described in JP-A No. 57-34502, uses 3 mmol perchloric acid as an eluent, a cation exchange resin in a column, and a pump that pumps a pH indicator after leaving the column. It consists of a reaction coil and a visible photometer, and requires a reaction system. On the other hand, a method in which ultraviolet detection is performed directly after column separation without using a reaction system is also widely used, but in this case, the range of analysis is extremely limited due to interference from other components coexisting in the sample. become.

[Problem to be solved by the invention]

The above-mentioned conventional technology has a complicated device configuration and smell, as it requires a reaction pump, a reaction coil, etc. in addition to sample separation. Furthermore, there are two problems with the direct method compared to the conventional method.

1. Detection method using an ultraviolet photometer, It is hindered by the difficulty of separating it from coexisting ultraviolet absorbing substances.

2. Detection method using conductivity detector, requires an auxiliary column (suppressor column) in the separation system.

The object of the present invention is to change the device configuration to include a pump, an injector,
Simplify columns, column ovens, detectors, data processors and mechanisms.

Conventionally, when using a cation exchange resin in a separation column, 3
Organic acids are analyzed by pumping millimolar perchloric acid and performing ion exclusion chromatography.

Here, by keeping the ion concentration in the eluent low, direct detection with a conductivity detector is possible. Controlling this perchloric acid concentration to a low level, improving separation quality and S/N, stabilizing the baseline, and improving quantitative accuracy6 Conductivity detection in actual sample measurements is limited to non-ionic substances. Since it has no sensitivity, it is effective for analyzing food samples such as coffee or soy sauce, as well as biological samples such as animal and plant extracts, which contain contaminants other than organic acids.

[Means to solve the problem]

The above purpose was achieved by lowering the perchloric acid concentration in the eluent composition from 3 mmol to 1/10, or 0.3 mmol.
This is achieved by reducing conductive dust to 1/1o and improving baseline stability.

[Effect]

When performing ion chromatography using a conductivity detector, the eluent concentration should be 1 to 0.3 to reduce background.
It is common to analyze in the millimole range.

In the analysis of organic acids, by lowering the eluent concentration from 3 mmol to 1.0.5 mmol to 0.3 mmol, baseline stability (background) can be lowered, separation is possible, and quantitative accuracy can be improved. can.

【Example〕

An embodiment of the present invention will be described below with reference to FIG.

Figure 1 is a flow path diagram of a liquid chromatograph, with 1 eluent, 2
It consists of a pump, 3 injectors, 4 columns, 5 chromatography data processing devices, 6 conductivity detectors, and 7 columns constant temperature bath.

FIG. 2 shows the elution time (position) when 0.3 mmol perchloric acid was fed as an eluent at a rate of 1 ml per minute and each organic acid was separated using a cation exchange resin.

Figure 3 shows an example of a standard mixed sample, and Figure 4 shows an example of soy sauce diluted 10 times with water and analyzed for 2oμQ.

When soy sauce is analyzed using an ultraviolet detector, the baseline is affected by impurities, but a stable baseline can be obtained.

〔Effect of the invention〕

According to the present invention, since organic acids are detected as ion conductive dust during detection in organic acid analysis, signals of non-ionic coexisting substances are not detected. That is, it has excellent selectivity, and
The baseline can be stabilized, the equipment can be simplified as there is no need for a reaction coil or a reaction liquid delivery system, and analysis work efficiency can be improved since there is no need to pre-process and remove non-ionic substances.

In addition, substances that are easily lost during extraction and concentration processes, such as acetic acid, are
Since the removal work of coexisting components can be omitted, the dilution rate can be lowered and quantitative performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a flow path diagram of an analysis system using the present invention.
FIG. 2 is a diagram showing elution of organic acids, FIG. 3 is a diagram showing an analysis example of an organic acid standard mixed sample, and FIG. 4 is a diagram showing an analysis example of 20 μQ of soy sauce after diluting it ten times. 1... Eluent, 2... Liquid pump, 3... Sample injector, 4... Separation column, 5... Data processing device, the first illusion of my dream

Claims (1)

[Claims] 1. Ion chromatography in liquid chromatography consists of a pump, sample injector, ion exclusion column (cation exchange resin made of styrene and divinylbenzene copolymer), column constant temperature bath, and conductivity detector. An organic acid analysis method characterized by using a combination of an analyzer and an eluent containing 2 mmol or less of an inorganic strong acid.