A ROAD LESS TRAVELED - NORMAL PHASE MICROBORE LIQUID-CHROMATOGRAPHY - MASS-SPECTROMETRY USING DIRECT LIQUID INTRODUCTION

Despite many heroic attempts, no liquid chromatography-mass spectrometry (LC-MS) interface has, to date, approached the sensitivity routinely obtained by gas chromatography (GC)-MS, although the range of analytes possible with LC-MS is certainly greater. One of the first LC-MS interfaces developed was direct liquid introduction (DLI), but the utility of DLI in reversed-phase applications has been limited. However, excellent results have been obtained for certain compounds by combining normal phase, microbore LC with DLI. Of particular interest are results using DLI to analyze for retinoids, a biologically important class of compounds. Quantitation of endogenous tretinoin and isotretinoin in human plasma has been demonstrated using this technique.