JPH06167485A - Analyzing method for boric acid - Google Patents

Abstract

PURPOSE:To simply and selectively analyze components of boric acid with high sensitivity by using a moving phase containing alcohols or sugars indicating coordination for the acid, and generating ionic complex or ester by a reaction with the acid in the phase. CONSTITUTION:Boric acid generates ionic complex or ester reversely to alcohols, sugars. A concentration of the alcohols, sugars, etc., contained in a moving phase is desirably 1mM or more, and in practice, polyvalent alcohols or sugars containing a plurality of hydroxyl groups are added. Electric conductivity of a background is extremely low and an analysis of higher sensitivity can be conducted under conditions in which any ionic substance i not added except neutral alcohols, sugars. A detecting lower limit concentration of the acid according to this method is considered to be 0.1ppm, and highly sensitive of ten times as large as that at the time of detecting with a differential refractometer. Further, selectivity is improved by employing an electric conductivity detecting method, and a stable analysis which is scarcely affected by influence of dissolved component is performed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to analysis of boric acid by high performance liquid chromatography (hereinafter abbreviated as HPLC) or ion chromatography (hereinafter abbreviated as IC).

[0002]

2. Description of the Related Art A differential refractometer detection method is generally used to analyze boric acid which does not show effective ultraviolet absorption and which has a high pKa and is difficult to ionize by using HPLC or IC. Since this detection method detects the difference in refractive index between the target component and the mobile phase, it can be applied to most components, but has the drawback of poor selectivity and low sensitivity.

Further, since boric acid is ionized in a mobile phase having a pH of 9 or more, it can be detected by an electric conductivity detection method. In addition to this, an absorption or fluorescence detection method by a derivatization method can also be applied.

[0004]

However, high pH
However, the method of detecting by the electric conductivity detection method still has problems such as when it is difficult to separate it from other components, or when it is necessary to separately use a pump for feeding the reaction reagent.

Further, the derivatization method has problems that special equipment is required, complicated operation is required, separation conditions and target components are limited. For this reason. In order to easily and accurately carry out the boric acid component with high sensitivity,
It requires some new detection method.

[0006] Therefore, an object of the present invention is to provide a new detection method capable of analyzing a boric acid component with high sensitivity.

[0007]

In order to solve the above-mentioned problems of the prior art, the inventor of the present application has diligently studied a selective and highly sensitive detection method of boric acid, and as a result, for example, alcohols or sugars By using the mobile phase contained, it is possible to generate an ionic complex or ester by the reaction of alcohols, sugars and boric acid in the mobile phase, and in this state it is possible to detect by an electrical conductivity detection method. I found it.

That is, according to the present invention, boric acid contained in a sample is subjected to ion chromatography using a mobile phase containing a component having a coordinating property with boric acid, and boric acid is a complex or ester with the above-mentioned component. Is detected by using an electric conductivity detector in a state of having an electric charge.

The column is, for example, an IC column "Shi".
m-pack SCR-102H "is used. However, any column may be used as long as it can analyze boric acid.

As an example of the mobile phase, a 25 mM mannitol aqueous solution is used. However, as long as the mobile phase contains a component having a coordinating property with respect to boric acid and can analyze boric acid, there is no restriction on the kind or concentration thereof.

The component having a coordinating property with respect to boric acid is
Examples include alcohols and sugars,
The concentration of alcohols and sugars contained in the mobile phase is 1
It is preferably at least mM. In addition, when neutral alcohols and saccharides are used, under the condition that no ionic substance other than these is added to the mobile phase, the background electric conductivity is remarkably low, and more sensitive analysis is possible.

Here, boric acid is known to reversibly form an ionic complex or ester with alcohols and saccharides, and the ease with which this ion is formed is determined by the hydroxyl groups and boric acid possessed by alcohols and saccharides. It depends on the positional relationship of the hydroxyl groups of. Practically, polyhydric alcohols or saccharides having a plurality of hydroxyl groups are added to the mobile phase.

The electric conductivity detecting method may be a method using a suppressor or a method not using the suppressor as in the embodiment.

[0014]

Thus, according to the present invention, by using a mobile phase containing alcohols or saccharides, it is possible to perform selective and highly sensitive analysis using a conductivity detection method at a pH condition of boric acid below pKa. It becomes possible.

[0015]

EXAMPLES The present invention will be described in more detail with reference to examples. The present invention is not limited to the examples below. FIG. 1 shows a flow chart of the IC device used in the present invention. In FIG. 1, 1 is a liquid feed pump, 2 is a sample introducer, 3 is a constant temperature bath, 4 is an electric conductivity detector, 5 is a data processor, 6 is a column, and 7 is a mobile phase.

The operation of one embodiment of the present invention using the analyzer shown in FIG. 1 will be described. First, the mobile phase 7 is fed by the liquid feed pump 1. The mobile phase is, for example,
It is a 25 mM mannitol aqueous solution. At equilibrium, the stationary phase surface of the column packing of 6 has a negative charge due to the ionization of cation exchange groups.

When a sample containing boric acid is introduced from the sample introduction device 3 by a microsyringe or the like, boric acid moves at a constant speed in the column according to the degree of formation of an anionic complex with mannitol. . The more alcohols or saccharides with large complex formation constants are used,
It is expected to elute earlier because of being easily excluded from the column and also to increase the peak intensity.

By monitoring the mobile phase continuously eluting from the column with the electric conductivity detector 4, an increase in conductivity at the elution position of boric acid is detected, and the signal at this time is sent to the data processor 5. It is transmitted and processed.

The specific analysis conditions are shown below. [Analysis conditions] Column: Shim-pack SCR-102H Transfer phase: 25 mM mannitol aqueous solution Flow rate: 1.0 mL / min Temperature: 40 ° C Detector: Electrical conductivity detector CDD-6A

The results of boric acid analysis carried out under the above analysis conditions are shown in FIG. FIG. 2 is an analysis example of boric acid collected by the method of the present invention. In the figure, a indicates the peak of boric acid, the horizontal axis is the elution time, and the vertical axis is the signal intensity. In this example, 0.
10 μL of a 5 mM boric acid aqueous solution is injected. The lower limit of detection of boric acid according to this method is considered to be 0.1 ppm or less, and it was found that the sensitivity was 10 times or more higher than that when a differential refractometer detector was used.

Further, since the selectivity is improved by adopting the electric conductivity detection method, stable analysis which is hardly influenced by coexisting components can be performed.

[0022]

INDUSTRIAL APPLICABILITY As described above, the present invention makes it possible to improve both selectivity and detection sensitivity in the analysis of boric acid by IC or HPLC.

[Brief description of drawings]

FIG. 1 shows an analyzer (ion chromatograph) used in an embodiment of the present invention.

FIG. 2 shows a chromatogram of a boric acid aqueous solution according to the present invention.

[Explanation of symbols]

 1: Liquid feeding pump 2: Sample introduction device 3: Constant temperature bath 4: Electric conductivity detector 5: Data processor 6: Column 7: Mobile phase

Claims (1)

[Claims] 1. Boric acid contained in a sample is subjected to ion chromatography using a mobile phase containing a component having a coordinating property with boric acid, and boric acid has a charge as a complex or ester with the above component. A method for analyzing boric acid, which is characterized in that it is detected by using an electric conductivity detector in a stable state.