Hair testing for cocaine and metabolites by GC/MS: criteria to quantitatively assess cocaine use

Abstract

A simple, rapid and sensitive method has been developed and validated for the determination of cocaine and its main metabolites (benzoylecgonine and cocaethylene) in human hair. The method involved solid-phase extraction with an Oasis HLB extraction cartridge and subsequent analysis by GC/MS. The limit of detection was 0.01 ng mg(-1) for cocaine, 0.04 for benzoylecgonine and 0.03 for cocaethylene. The method validation included linearity (with a correlation coefficient >0.99 over the range 0.2-50 ng mg(-1) ), intra- and inter-day precision (always lower than 12%) and accuracy (mean relative error always below 17%) to meet the bioanalytical acceptance criteria. The procedure was further applied to 40 hair samples from self-reported cocaine users arrested by the police who provided a positive urine-analysis for cocaine, and was demonstrated to be suitable for its application in forensic toxicology. New approaches were raised to detect false-negative results that allow a better interpretation of hair testing results.

Norcocaine and cocaethylene distribution patterns in hair samples from light, moderate, and heavy cocaine users

“…Our data concur with hair testing studies that reported lower levels of BEG than COC 13, 17, 19. The basic drug COC has a greater affinity for melanine than for BEG, its amphoteric metabolite 19.…”

“…COC levels were above 0.5 ng/mg (ranging from 1.63 to 39.29 ng/mg) in all samples. Mean COC concentration was 9.49 ng/mg, indicating that most patients used COC regularly 13, 19. BEG levels, which were determined in all hair samples, were above 0.05 ng/mg (ranging from 0.19 to 5.77 ng/mg, mean value 1.40).…”

“…Since CE is considered a metabolic marker rather than a contaminant its presence in hair samples can be accepted as sufficient proof of COC intake. In fact, a CE/COC ratio over 0.02 was recently proposed as an additional new criterion for a positive hair test 19. However, since COC is transesterified by hepatic carboxylesterase into CE only when COC and alcohol have been ingested simultaneously,19 CE cannot be considered a universal marker of active COC use.…”

Magnetic Lateral Flow Strip for the Detection of Cocaine in Urine by Naked Eyes and Smart Phone Camera

“…Instrument analysis methods involve high performance liquid chromatography (HPLC) [3], liquid chromatography-mass spectrometry (LC-MS) [4,5], gas chromatography-mass spectrometry (GC-MS) [6,7], and capillary electrophoresis-mass spectrometry (CE-MS) [8], etc. These methods are highly sensitive and accurate.…”

Desenvolvimento de método de triagem de substâncias psicoativas em amostras de cabelo através de técnicas imunológicas

“…Por se tratar de um composto naturalmente anfótero, a benzoilecgonina é comumente extraída pela técnica de SPE, especialmente por cartuchos de fase mista que permitem tanto a sua extração quanto da própria cocaína e outros produtos de biotransformação (ALESKA et al, 2012;MUSSHOFF et al, 2009;LÓPEZ-GUARNIDO et al, 2013;GOUVEIA et al, 2012;BARROSO et al, 2008). Embora a técnica de extração por SPE seja amplamente utilizada, técnicas miniaturizadas como a LPME e a SPME são a tendência atual, como já mencionado (BACIU et al, 2015).…”