Recent Trends in MALDI-MS Drugs Analysis in Human Hair: Pre-Analytical and Analytical Challenges and Pitfalls

The value of hair in forensic toxicology has already been widely demonstrated. It offers a much wider detection window than other matrices, and its segmental analysis allows the documentation of a single, occasional or regular consumption of a large number of molecules. To date, considerable efforts are being made to achieve very high sensitivity using increasingly effective techniques in the forensic analysis of hair (gas chromatography with electron ionization mass spectrometry (GC--EI-MS); gas chromatography with chemical ionization mass spectrometry (GC--CI-MS); gas chromatography-tandem mass spectrometry (GC--MS-MS); high or ultra performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS and UPLC-MS-MS)). Since the early 2000s, work has been carried out to analyze hair using matrix-assisted laser desorption ionization (MALDI) coupled with imaging mass spectrometry (IMS). Intact, cut or pulverized, human head hairs are analyzed in all their forms. With a simplified and rapid sample preparation protocol, MALDI-IMS appears to be an attractive option for the forensic interpretation of hair analysis. The high spatial resolution clearly competes with conventional methods and strand segmentation. This article provides a complete overview on MALDI techniques used and its applications to better understand the pre-analytical and the analytical parts in the hair analysis.