A possible new oxidation marker for hair adulteration: Detection of PTeCA (1H‐pyrrole‐2,3,4,5‐tetracarboxylic acid) in bleached hair

Abstract

Hair analysis has become a valuable tool in forensic toxicology to assess drug or alcohol abstinence. Yet, hair adulteration by cosmetic products presents a major challenge for forensic hair analysis. Oxidative treatments, e.g. bleaching, may lead to analyte loss and thereby to false negative results. Currently, the eumelanin degradation product 1H-pyrrole-2,3,5-tricarboxylic acid (PTCA) serves as a marker for oxidative hair treatment, but requires the definition of cut-off values. To investigate further eumelanin degradation products as markers for oxidative hair treatment, hair samples with and without in vitro bleaching (hydrogen peroxide (H 2 O 2 ) concentrations 1.9% up to 12%; incubation times 15 min, 30 min, 60 min) were analyzed by liquid chromatography coupled to high-resolution time of flight mass spectrometry (HPLC-HRMS). The distribution of eumelanin degradation products along the hair shaft was investigated for routine applicability after segmentation of cosmetically untreated hair samples and authentically treated hair samples. The signals of the eumelanin degradation products PTCA, 1H-pyrrole-2,-3,4-tricarboxylic acid (isoPTCA), and 1H-pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) were found to be significantly elevated after in vitro bleaching already with low H 2 O 2 concentrations and after short incubation times. In contrast to PTCA and isoPTCA, PTeCA was not detectable in cosmetically untreated segments up to 12 cm from hair root and was only formed through the oxidation process. The results of the study show that the detection of PTeCA within the proximal 3 to 6 cm segment can be applied to reliably detect hair adulteration attempts through hair bleaching. K E Y W O R D Shair biomarker, melanin degradation, oxidative hair treatment, PTCA, PTeCA

Cheating on forensic hair testing? Detection of potential biomarkers for cosmetically altered hair samples using untargeted hair metabolomics

“…34 Through oxidation processes or UVA-induced photoaging, it can be degraded by oxidation and/or cross-linking of its indole-moieties. [35][36][37] In line with previous work, 13,14 the applied untargeted workflow allowed for the detection of the eumelanin degradation products PTCA, 1H-pyrrole-2,3,4-tricarboxylic acid (isoPTCA) and PTeCA either as significantly increased (PTCA, isoPTCA) or as newlyformed (PTeCA) after bleaching. 13,14 This consistence proofs the general applicability of the current untargeted workflow to detect potential markers for oxidative hair treatment.…”

“…Screening for potential differing metabolites due to oxidative hair treatment was performed with a previous evaluated LC-HRMS method. 14,20 To avoid errors resulting from varying instrument performances over time, all samples were analyzed in randomized order and direct comparison of sample results was only performed within one batch. The analytical performance and the reproducibility of the batch analyses were monitored by deviation of RT and peak areas in SST and pooled QC samples.…”

“…Recently, 1H-pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) was identified to be exclusively formed through oxidative hair treatment which would in theory facilitate the detection of bleached hair samples as cut-off values do not need to be determined. 14 At the moment, the current lack of commercially available reference standards and its melanin dependency still hinders its routine applicability. Hence, the need for further reliable markers for cosmetic hair treatments is more than relevant to date and new concepts for biomarker search are required.…”

Towards Best Practice in Hair Metabolomic Studies: Systematic Investigation on the Impact of Hair Length and Color

“…Within this study, we could show that the hair metabolome depends on the hair color and changes along the hair strand in an entirely natural way. Additionally, it has been shown that cosmetic hair treatments significantly affect the detectability of endogenous compounds [ 6 , 18 , 19 ]. These aspects are not considered in published hair metabolomic studies so far, which highlights the urgent need to raise attention to this topic.…”

Hyphenated high-resolution mass spectrometry—the “all-in-one” device in analytical toxicology?

“…Besides conventional GC-or LC-MS methods, LC-HRMS was established particularly for untargeted metabolomics studies, again because of its high specificity, sensitivity, and flexibility [58][59][60][61][62][63]. There are two main application fields, one focusing on the change of the endogenous compounds under the influence of drug administration [62,[64][65][66][67][68][69] or sample manipulation [65,[70][71][72][73][74] and one on the use of metabolomics techniques for investigating the metabolism of new drugs, namely of NPS [60,61,75]. Metabolomics could also play a role in doping control, e.g., for detecting hormone abuse considering that hormones have a strong influence on human endogenous metabolism changing several endogenous parameters [76].…”