This study aims to achieve high spatial-resolution tandem mass spectrometry (MS/MS) imaging for depicting longitudinal and transverse distribution of drugs in hair, which can provide indispensable information for the proper interpretation of hair test results, including the mechanism of drug incorporation into hair. Two types of hair samples were obtained and analyzed: User's Hair, sampled from a volunteer who took an over-the-counter medicine containing methoxyphenamine (MOP), a nonregulated analogue of methamphetamine; and Soaked Hair, prepared by soaking blank hair in MOP solution. Longitudinal and transverse-sectioning of single hair shafts was accomplished by freeze-sectioning using customized microtomes. Vapor deposition of α-cyano-4-hydroxycinnamic acid provided the finest matrix layer (resolution <1 μm, 0.7-μm thickness), although it provided less effective ionization of MOP compared to aerosol spraying or a combination of both. Matrix-assisted laser desorption/ionization (MALDI)-ion trap (IT)-time-of-flight (TOF) MS/MS permitted the imaging of trace-level MOP in hair with a MS/MS window setting of ±0.02 Da and a spatial resolution setting at 5 or 10 μm. For Soaked Hair, localization of MOP in the peripheral part was clearly depicted, but no such biased distribution was observed in the transverse sections of User's Hair. MOP-positive bands generated corresponding to the time periods of MOP intake could be observed on the longitudinal sections of User's Hair. This method can provide forensically crucial information regarding hair analysis for drugs: drug incorporation mechanism into hair, discrimination of undesired surface contamination from endogenous incorporation of ingested drugs, and precise elucidation of drug-use history.

中文翻译：

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高空间分辨率基质辅助激光解吸/电离-离子阱飞行时间串联质谱成像，用于描述掺入头发中的药物的纵向和横向分布。

这项研究旨在实现高空间分辨率串联质谱（MS / MS）成像，以描绘头发中药物的纵向和横向分布，这可以为正确解释头发测试结果提供必不可少的信息，包括药物掺入机制头发。获得并分析了两种类型的头发样本：用户的头发，是从服用非处方药物甲氧基苯胺（MOP）的非处方药物中抽取的；将头发浸入MOP溶液中制成浸透的头发。通过使用定制的切片机进行冷冻切片，可以完成单根发干的纵向和横向切片。α-氰基-4-羟基肉桂酸的气相沉积提供了最细的基质层（分辨率<1μm，厚度为0.7μm），尽管与雾化喷雾或两者结合相比，它提供的MOP电离效果不佳。基质辅助激光解吸/电离（MALDI）-离子阱（IT）飞行时间（TOF）MS / MS可以对头发中的痕量MOP成像，MS / MS窗口设置为±0.02 Da，并且空间分辨率设置为5或10μm。对于浸湿的头发，清楚地描绘了MOP在外围部分的定位，但是在使用者的头发的横截面中没有观察到这种偏斜的分布。可以在使用者的头发的纵断面上观察到与MOP摄入时间段相对应的MOP阳性带。此方法可以提供有关药物毛发分析的法证关键信息：药物掺入头发的机理，