Drugs incorporated into hair are exposed to the environment, and cosmetic and chemical treatments, with possible decreases in their content. Knowledge concerning the effect of sunlight on drug content in hair can be helpful to forensic toxicologists, in particular, when investigating drug concentrations above or below pre-determined cut-offs. Twenty-eight authentic positive hair samples were selected which had previously tested positive for ethyl glucuronide (EtG). Washed hair were divided into two identical tufts, with the former exposed at 13,219 J/cm2 (300-800 nm spectrum of irradiance) for 48 h in a solar simulator, and the latter kept in the dark. Hair samples were extracted and analyzed by ultra performance liquid chromatography-tandem mass spectrometry. The percentage of photodegradation was calculated for EtG. In parallel, photodegradation processes of standard molecule dissolved in aqueous and organic solutions were studied. In 28 hair samples, positive for the targeted analyte, exposure to artificial sunlight induced an appreciable increase in EtG concentrations. The concentration range in the non-irradiated hair samples was 6.0-772.0 pg/mg, and 64.3% of samples exhibited an increase in post-irradiation samples, ranging from 7% to 255%. In seven cases, a decrease was observed ranging from -5.0% to -36.0%. Thus, either a decrease or an increase of EtG may be observed post-irradiation, depending on hair color and/or hair thickness. Because the denaturation status of hair fibers and the thickness of hair before irradiation could play a role, a scanning electron microscope study should be envisaged.

中文翻译：

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人工阳光照射下头发中乙醛糖醛酸乙酯光稳定性的研究。

掺入头发中的药物会暴露于环境以及美容和化学处理中，其含量可能会减少。有关日光对头发中药物含量的影响的知识可能对法医毒理学家有所帮助，特别是在调查药物浓度高于或低于预定的临界值时。选择了28个真实的阳性头发样本，这些样本先前已对乙基葡萄糖醛酸（EtG）测试为阳性。将洗过的头发分成两个相同的簇，在太阳模拟器中，前者在13,219 J / cm2（300-800 nm的辐照度光谱）下暴露48小时，而后者则保持在黑暗中。提取头发样品并通过超高效液相色谱-串联质谱分析。计算出EtG的光降解百分比。在平行下，研究了溶于水和有机溶液中的标准分子的光降解过程。在28个针对目标分析物呈阳性的头发样本中，暴露于人造阳光下会导致EtG浓度明显增加。未经辐照的头发样品中的浓度范围为6.0-772.0 pg / mg，辐照后样品中64.3％的样品有所增加，范围从7％到255％。在七种情况下，观察到的下降幅度为-5.0％至-36.0％。因此，根据头发的颜色和/或头发的厚度，辐照后EtG可能会降低或增加。由于头发纤维的变性状态和辐照前头发的厚度可能起一定作用，因此应设想进行扫描电子显微镜研究。