Abstract
Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) has been employed to rapidly screen longitudinally sectioned drug user hair samples for cocaine and its metabolites using continuous raster imaging. Optimization of the spatial resolution and raster speed were performed on intact cocaine contaminated hair samples. The optimized settings (100 × 150 μm at 0.24 mm/s) were subsequently used to examine longitudinally sectioned drug user hair samples. The MALDI-MS/MS images showed the distribution of the most abundant cocaine product ion at m/z 182. Using the optimized settings, multiple hair samples obtained from two users were analyzed in approximately 3 h: six times faster than the standard spot-to-spot acquisition method. Quantitation was achieved using longitudinally sectioned control hair samples sprayed with a cocaine dilution series. A multiple reaction monitoring (MRM) experiment was also performed using the ‘dynamic pixel’ imaging method to screen for cocaine and a range of its metabolites, in order to differentiate between contaminated hairs and drug users. Cocaine, benzoylecgonine, and cocaethylene were detectable, in agreement with analyses carried out using the standard LC-MS/MS method.Graphical ᅟ
Highlights
Hair testing is a powerful tool routinely used for the detection of drugs of abuse in toxicology and forensic applications [1,2,3]
To determine the optimal spatial resolution and raster speed intact cocaine contaminated hair samples were analyzed in triplicate, and these results were plotted as a function of the average intensity and time, respectively
Using the calibration curve the concentration of cocaine per segment for the first user was determined to be 0.437, 0.389, 0.340, and 0.305 ng/mm2 (1–4), whereas the concentration of cocaine per segment for the second user was determined to be 0.151, 0.154, 0.1720, and 0.186 ng/mm2 (1–4). These results indicate both users have a prolonged history of cocaine use and that the first user is a heavier user in contrast to the second user; this is apparent in in the MALDI-MS/MS image
Summary
Hair testing is a powerful tool routinely used for the detection of drugs of abuse in toxicology and forensic applications [1,2,3]. In the work reported here, instrumental and experimental parameters were optimized to rapidly generate high quality images of longitudinally sectioned drug user hair samples using continuous raster imaging.
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