Analysis of Cocaine, Benzoylecgonine, and Ecgonine Methyl Ester in Hair Strands Via Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS)

Hair can provide chemical information about drug use. This study employed matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) to detect drugs in hair samples. The technique was used to detect cocaine (COC, molecular weight (Mw) = 303.14 Da) and its main metabolites, benzoylecgonine (BZE, Mw = 289.13 Da), cocaethylene (COCE, Mw = 317.16 Da) and ecgonine methyl ester (EME, Mw = 199.12 Da) in hair strands using 2,5-dihydroxybenzoic acid (DHB, 7.0 mg mL-1) and α-cyano-4-hydroxycinnamic acid (CHCA, at concentrations of 1.5, 3.0, 7.0, and 10 mg mL-1) as the evaluated matrices. Among these, CHCA was selected. Subsequently, the qualitative results obtained by MALDI(+) MS were correlated with the quantitative analyses of gas chromatography-mass spectrometry (GC-MS), demonstrating a significant correlation in responses (70%), with the detection of analytes by MALDI(+) MS even at low concentrations, determined by GC-MS. The concentration ranges obtained by GC-MS analysis were from 0.6 to 4.1 ng mg-1 of COC, and from 0.05 to 0.4 ng mg-1 of COCE. The effect of pre-washing on the detection of COC and its metabolites was also evaluated, and the results indicated less influence from the pre-washing stage and confirmed the reduction in COC detection in hair exposed to bleaching.