Mass spectrometric determination of n-hydroxyphenacetin in urine using multiple metastable peak monitoring following thin-layer chromatography

This work describes a method for the quantitative determination of the labile, toxic N-hydroxy metabolite of phenacetin in urine. A thin-layer chromatography step was used for the preliminary purification of extracts, and the specificity of the assay was based on the monitoring of specific metastable decompositions in a forward geometry double-focussing mass spectrometer, in a manner analogous to conventional tandem mass spectrometry. This precluded the need for a gas chromatographic separation, thus minimizing thermal decomposition which can occur with these compounds, as well as enabling very rapid analyses.