Direct combination of immersed single-drop microextraction with atmospheric pressure matrix-assisted laser desorption/ionization tandem mass spectrometry for rapid analysis of a hydrophilic drug via hydrogen-bonding interaction and comparison with liquid-liquid extraction and liquid-phase microextraction using a dual gauge microsyringe with a hollow fiber

This study presents the feasibility of direct coupling of the immersed single-drop microextraction (SDME) technique with atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) for the rapid analysis of a hydrophilic drug (dopamine) from aqueous solution and human urine in an ion trap tandem mass spectrometer through hydrogen-bonding interaction of dopamine with the extraction solvent (octanol). The optimum conditions for the SDME experiments coupled to AP-MALDI/MS were: stirring rate, 240 rpm; extraction time, 5 min; sample pH value, 8; and matrix concentration, 2000 ppm, using alpha-cyano-4-hydroxycinnamic acid (alpha-CHCA) as matrix. The limits of detection (1,0131s) for the SDME/AP-MALDI-MS experiments were 25 and 40 ppm in water and human urine, respectively. In a comparison of this method with the traditional liquid-liquid extraction (LLE), the SDME method shows better LODs than the LLE (40 ppm) and the same LODs (25 ppm) as the liquid-phase microextraction using a dual gauge microsyringe with a hollow fiber (LPME/DGM-HF). However, the SDME method is more convenient than the LPME/DGM-HF method. Copyright (c) 2006 John Wiley & Sons, Ltd.