PTCA (1H‐pyrrole‐2,3,5‐tricarboxylic acid) as a marker for oxidative hair treatment

Abstract

Hair analysis for the assessment of alcohol or drug abstinence has become a routine procedure in forensic toxicology. Hair coloration leading to loss of incorporated xenobiotics and to false negative results has turned out to be a major problem. Currently only colored extracts provide hints of manipulations but not bleaching. A liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed and validated to determine 1H-pyrrole-2,3,5-tricarboxylic acid (PTCA), a major oxidation product of melanin. PTCA was determined in natural hair samples (n = 21) after treatment with 3% hydrogen peroxide (H O ) for 30 or 40 minutes with concentrations up to 12% for 40 minutes. In another series, 12 natural hair samples were submitted to different coloration procedures (henna, tinting, semi-permanent and permanent dyeing, bleaching) and the changes in PTCA content were determined. A significant increase in the PTCA content was found for both incubation times and increasing H O concentrations. Coloration with henna or tinting had no influence on PTCA levels detected, but a significant increase was observed after semi-permanent and permanent dyeing and bleaching. As PTCA concentrations in natural hair were found to be in a range of <2.1-16.4 ng/mg (8.4 ± 3.8 ng/mg, mean ± SD, n = 33), a cut-off of 20 ng/mg is recommended for the distinction between natural vs. excessively oxidized hair. In case of naturally low melanin content (light-blond or white hair), no marked increase in PTCA may occur. The present study demonstrated that PTCA is formed during oxidative treatment of melanin in hair, which can be used to detect previous hair coloration including oxidation.

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

“…Heavy-labeled and deuterated internal standards (IS) adenosine ribose-D 1 , arginine-13 C 6 , caffeine 3-methyl-13 C, carnitine trimethyl-D 9 , deoxycholic acid-D 4 , D-fructose 13 Venice bleaching oxidation powder) were purchased from DOBI (Suhr, Switzerland). Heavy-labeled and deuterated internal standards (IS) adenosine ribose-D 1 , arginine-13 C 6 , caffeine 3-methyl-13 C, carnitine trimethyl-D 9 , deoxycholic acid-D 4 , D-fructose 13 Venice bleaching oxidation powder) were purchased from DOBI (Suhr, Switzerland).…”

“…13 Within the present, preliminary study, the analysis of further eumelanin degradation products, their formation under different conditions and the applicability F I G U R E 3 Mean and SD (n = 3) of analyte peak area ratios (yaxis: Compound/sample weight) of PTCA, isoPTCA and PTeCA in dependence of increasing H 2 O 2 concentrations (1.9%, 3%, 6%, 9%, and 12%) and incubation times (15 min, 30 min, 60 min) (x-axis) (experiment 2) F I G U R E 2 Box plots for PTCA, isoPTCA, and PTeCA. Previous studies identified the eumelanin degradation product PTCA as a marker for oxidative hair treatment, however requiring the consideration of cut-off values.…”

“…13 Nevertheless, it remains unclear which hair segments were used for the determination of PTCA contents in that study. Interindividual differences are therefore high.…”

“…PTCA was obtained as an analytical reference standard from ChemPur (Karlsruhe, Germany). Heavy-labeled and deuterated internal standards (IS) adenosine ribose-D 1 , arginine-13 C 6 , caffeine 3-methyl- 13 C, carnitine trimethyl-D 9 , deoxycholic acid-D 4 , D-fructose 13 Venice bleaching oxidation powder) were purchased from DOBI (Suhr, Switzerland). and experiment 4 (segmentation of untreated hair samples).…”

“…Only recently, Petzel-Witt et al 13 identified 1H-pyrrole-2,-3,5-tricarboxylic acid (PTCA), an eumelanin degradation product, as a marker for oxidative hair treatment by using liquid-chromatography tandem-mass spectrometry (LC-MS/MS). Their studies revealed that PTCA concentrations significantly increased after in vitro bleaching of the hair samples.…”