Investigations on antipyrine metabolism. II--Analysis of conjugated metabolites of antipyrine in rat and human urine by off-line combination of liquid chromatography and field desorption mass spectrometry.

The complex pattern of conjugates in the metabolism of antipyrine in man and rat has been investigated using an off-line combination of liquid chromatography and field desorption mass spectrometry. Using this approach, field desorption mass spectrometry enables the direct identification of underivatized glucuronides and sulphates in antipyrine metabolism on the basis of the corresponding protonated or cationized molecules representing the base peaks in the field desorption mass spectra. All conjugated metabolites of antipyrine established so far--four glucuronides and three sulphates--were identified in extracts of urine after stepwise purification by column chromatography and subsequent mass spectrometric analysis.