Derivatives for the identification and quantitative determination of some keto and aldo-carboxylic acids by gas-liquid chromatography

Abstract

Studies on the derivatives of some physiologically and pathologically important keto and aldo-acids (pyruvic, glyoxylic, 2-oxoglutaric, oxaloacetic and 4-hydroxyphenylpyruvic) have shown that the O-ethoxime trimethylsilyl esters are the most suitable for quantitative gas-liquid chromatography. The O-trimethylsilyl oxime trimethylsilyl esters were thermally unstable under the conditions used. The O-methyl and O-benzyl oxime trimethylsilyl esters are also suitable for gas-liquid chromatography and would be useful in identification studies. The O-benzyl oxime trimethylsilyl derivatives are suggested as being especially suitable when only the keto and aldo-acids are to be studied, and it is not necessary to identify the lower boiling trimethylsilyl esters of other carboxylic acids on the same chromatogram. Two aldehyde-specific reagents, dimedone and NN′-diphenylethylenediamine, were also examined for use with glyoxylic acid. The trimethylsilyl ester of 1,3-diphenylimidazolidine-2-carboxylic acid (the derivative of glyoxylic acid with NN′-diphenylethylenediamine) has a high boiling-point and is suitable for quantitative gas-liquid chromatography. This derivative should be especially useful in studied that are particularly concerned with the metabolism of glyoxylic acid or possibly other aldehydes. The retention times of the derivatives relative to the retention times of n-tetracosane and n-hexacosane are compared with the corresponding values for the trimethylsilyl derivatives of some physiologically related carboxylic acids that do not contain keto or aldo groups.