Determination of sulphonamides by electron-capture gas chromatography. Preparation and properties of perfluoroacyl and pentafluorobenzyl derivatives.

The derivatization of benzenesulphonamide, N-ethylbenzenesulphonamide and N-phenylbenzenesulphonamide with trifluoroacetic and heptafluorobutyric anhydride and pentafluorobenzyl bromide has been studied. A rapid quantitative acylation is obtained in benzene in the presence of trimethylamine. Pentafluorobenzylation is performed by the extractive alkylation technique using tetrabutylammonium as counter ion and methylene chloride as solvent. Less than 20 min are required for a quantitative derivatization. The derivatized sulphonamides have a hydrophobic character, making them very suitable for gas chromatography. Trifluoroacetylation and heptafluorobenzylation decreases it. The derivatives have a high electron-capture detector response (minimum detectable quantity, 1-2 X 10-minus 16 moles/sec). A standard curve is given for the determination of N-phenylbenzenesulphonamide as trifluoroacetyl derivative in the range 1.8-90 ng/ml.