Over the years, several studies have shown that many factors are likely to affect the results of forensic hair analyses and complicate their interpretation. Among these factors, one of the major drawbacks in hair analysis is the affectability of deposited xenobiotics by cosmetic treatments which could be eventually used to adulterate the sample. It is well known that some cosmetic treatments containing hydrogen peroxide, such as permanent dyeing or bleaching, lead to the formation of 1-H‐pyrrole‐2,3,5‐tricarboxylic acid (PTCA), a melanin degradation product. Considering that PTCA is also an endogenous compound, spontaneously formed by natural oxidation of melanin, its only detection in hair is not enough to confirm a cosmetic oxidative treatment. For this reason, the aim of the present work was to develop and validate a reliable liquid-liquid extraction method in ultra-high-performance liquid chromatographic–tandem mass spectrometry for the determination of endogenous PTCA in hair from a wide multi-ethnic population (African, Arab, Asian-Pacific, Caucasian, Hispanic, Indian). According to previous studies, untreated hair samples showed a PTCA content of 8.54 ± 5.72 ng/mg (mean ± SD), ranging between 0.44 and 23.7 ng/mg; after in vitro cosmetic bleaching, PTCA increased to 16.8 ± 6.95 ng/mg (range 4.16–32.3 ng/mg). Comparing baseline PTCA levels of each subgroup with the others, we could not observe any statistically significant difference, except for Caucasians (p < 0.05), wherein the concentrations were lower. Further studies and a wider sampling are necessary to elucidate the role of PTCA as diagnostic marker of cosmetic hair treatment in forensic field.

中文翻译：

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头发中的内源性1-H-吡咯-2,3,5-三羧酸（PTCA）及其法医学应用：广泛的多民族人群的初步研究。

多年来，数项研究表明，许多因素可能会影响法医头发分析的结果并使解释复杂化。在这些因素中，头发分析的主要缺点之一是美容处理对沉积的异种生物的影响，该美容处理最终可用于掺假样品。众所周知，某些含有过氧化氢的美容处理（例如永久性染色或漂白）会导致黑色素降解产物1-H-吡咯-2,3,5-三羧酸（PTCA）的形成。考虑到PTCA也是一种内源性化合物，它是由黑色素的自然氧化自发形成的，因此仅在头发中检测到它不足以确认化妆品的氧化处理。为此原因，当前工作的目的是开发和验证一种可靠的液-液萃取方法，用于超高效液相色谱-串联质谱法，用于测定来自多个族裔群体的头发中的内源性PTCA（非洲，阿拉伯，亚太，高加索，西班牙裔，印度）。根据先前的研究，未经处理的头发样本的PTCA含量为8.54±5.72 ng / mg（平均值±SD），范围为0.44至23.7 ng / mg；后在体外化妆品漂白中，PTCA增至16.8±6.95 ng / mg（范围4.16–32.3 ng / mg）。将每个亚组的基线PTCA水平与其他亚组进行比较，除高加索人（p <0.05）浓度较低外，我们没有观察到任何统计学上的显着差异。为了阐明PTCA在法医领域中用于美容性头发治疗的诊断标志物的作用，有必要进行进一步的研究并进行更广泛的采样。