RT Journal Article
T1 Chemical Straightening as a Source of Analytical Variability in Hair Testing: A Dual-Analyte Case Report
A1 Blanco Ces, Miriam
A1 Castro Ríos, Ana de
A1 Cobo Golpe, María
A1 López Rabuñal, Ángela
A1 Cruz Landeira, Angelines
A1 Lendoiro Belío, Elena
K1 Alprazolam
K1 Cosmetic treatment
K1 GHB
K1 Hair
K1 LC-MS/MS
AB Hair analysis is increasingly used in forensic toxicology; however, result interpretation may be influenced by cosmetic hair treatments. Although the effects of bleaching, dyeing, and thermal straightening have already been evaluated, data on permanent chemical hair straightening are scarce, particularly under in vivo conditions. This case report evaluates the impact of an alkaline-based permanent hair straightening procedure on the determination of an endogenous compound, gamma-hydroxybutyrate (GHB), and an exogenous drug, alprazolam, in hair. Hair samples were collected from a 39-year-old woman before and 1 month after undergoing chemical hair straightening based on ammonium thioglycolate. Adjacent hair strands corresponding to identical temporal windows were analyzed. GHB was quantified in 0.5-cm hair segments using a validated liquid chromatography–tandem mass spectrometry (LC-MS/MS) method, whereas alprazolam was analyzed in 2-cm segments using a validated LC-MS/MS method for drugs of abuse and psychoactive pharmaceuticals. All analyzed segments were positive for GHB in both samples. After the straightening procedure, endogenous GHB concentrations showed a pronounced increase compared with pretreatment levels, with fold changes ranging from approximately 6 to 43 in corresponding segments. In contrast, alprazolam concentrations in segments corresponding to the reported period of drug intake decreased by approximately 1.7- to 2-fold following chemical straightening. This case report demonstrates that permanent chemical hair straightening can produce marked and analyte-dependent effects on hair drug concentrations. These findings emphasize the importance of systematic documentation of cosmetic hair treatments and careful interpretation of hair analysis results in forensic casework, particularly when analyte concentrations are low.
PB Wiley
SN 1942-7603
YR 2026
FD 2026-04-08
LK https://hdl.handle.net/10347/47282
UL https://hdl.handle.net/10347/47282
LA eng
NO Blanco-Ces, M., de-Castro-Ríos, A., Cobo-Golpe, M., López-Rabuñal, Á., Cruz, A., & Lendoiro, E. (2026). Chemical Straightening as a Source of Analytical Variability in Hair Testing: A Dual-Analyte Case Report. "Drug Testing and Analysis". https://doi.org/10.1002/DTA.70071
DS Minerva
RD 23 may 2026