Analytical Sciences

Improvement of Extractive Alkylation Gas Chromatography of Short-chain Carboxylic Acids in Aqueous Solution

Shigemi UEDA,* Noriyuki TAKEMOTO,** Risa ONODERA,** Shinji TSUNOI,*** and Ikuya SHIBATA***

*CMC Analysis Laboratory, Toray Research Center, Inc., 9-1 Oe-cho, Minato, Nagoya, Aichi 455-8502, Japan
**Organic Analysis Laboratory, Toray Research Center, Inc., 3-3-7 Sonoyama, Otsu, Shiga 520-8567, Japan
***Research Center for Environmental Preservation, Osaka University, 2-4 Yamadaoka, Suita, Osaka 565-0871, Japan

In the analysis of short-chain carboxylic acids such as formic acid and acetic acid in aqueous solution using extractive alkylation gas chromatography, tetrahexylammonium bromide (THAB) as a phase-transfer catalyst (PTC) causes a high intensity and broad peaks in the gas chromatogram, and interfere with the detection of carboxylic acid derivatives. By an easy treatment of the extractive alkylation solution with perchloric acid and n-hexane, it is possible to remove more than 95% of THAB, and to provide good gas chromatogram with a little admixture of carboxylic acid derivatives. The desensitization was 16% at the maximum, the contamination of the glass insert in gas chromatograph and liquid phase in column by THAB was minimized, and trouble in continuous measurement could be avoided.

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