Abstract

This report describes the development of a new method for the analysis of the tuberculostaticum isoniazid in human serum. The Laboratory of Chemotherapy needed a sensitive method for the analysis of this compound, which is also useful for complex matrices (e.g. sera of nephritic patients). The developed method is based on a one-step derivatization of isoniazid with pentafluorobenzoylchloride in buffered alkaline aqueous samples. First, reaction takes place on the azid moiety, followed by an intermolecular rearrangement leading to a stable, non-polar derivative, which is easily extracted (>95%) and has excellent gaschromatographic properties. The reaction is rapic (<20 min) and almost pH-independant above pH=7. Highest yields (> 95%) were obtained with strong buffercapacities (1-3 molar) of the sample. For serumsamples, prior proteinprecipitation was necessary in order to obtain similar recoveries as for aqueous standards. The derivative was highly sensitive for negative-ion-chemical-ionization. The detection limit for serum was better than 0.1 mug/ml with sample sizes of 0.5 ml or less.