High-Throughput Monitoring of Cocaine and Its Metabolites in Hair Using Microarrays for Mass Spectrometry and Matrix-Assisted Laser Desorption/Ionization-Tandem Mass Spectrometry

Because of inhomogeneous matrix-assisted laser desorption/ionization (MALDI) matrix crystallization and laser shot-to-shot variability, quantitation is not generally performed by MALDI mass spectrometry. Here we introduce a high-throughput MALDI method using an innovative high-density microarray for mass spectrometry (MAMS) technology, which allows semiquantitative measurement of cocaine and its metabolites, benzoylecgonine, cocaethylene, and ecgonine methyl ester. A MAMS slide containing lanes of hydrophilic spots and an automated slider to drag a sample droplet over several small spots can accomplish automatic sample aliquoting and lead to homogeneous crystallization of the matrix–analyte mixture and, thus, to a reproducible signal (average RSD 6%). Four hair samples of self-reported drug users were analyzed in parallel by MALDI-MS/MS and by a validated LC–MS/MS method. The consumption profiles as well as the metabolite-parent drug ratios obtained correlated well, confirming the effectiveness of the MAL...