gms | German Medical Science

Objective: Hair analysis is recognized as a suitable method for the assessment of long term use of drugs of abuse. In the present paper we describe the development of a new methodology aiming to detect and quantify the presence of amphetamines and cocaine and their metabolites in hair from human subjects including samples of narcotic drug users.

Material/Methods: Hairs were obtained from drug-free humans and were used for method development: All hair samples were washed with water, followed by acetone and finally with dichloromethane. Thirty mg of washed hairs were spiked with the analytes of interest and internal standards, and the sample was subsequently extracted with methanol. Following centrifugation, the extract was evaporated to dryness and BSTFA (1%TMCS) was added to the dry residue. Following derivatisation, analysis was conducted on GC-MS with selected ion monitoring (SIM). The analytes included: cocaine, benzoylecgonine, ecgonine methyl ester, amphetamine, methamphetamine, MDA, MDMA. Internal standards from each category were added (in total three standards).

Results: First the GC-MS (electron impact) analytical method was optimized to reach the best chromatographic separation and highest sensitivity. Three ions were selected for each analyte for SIM and one of these three ions was used for quantitation. Next, the methodology applied for the derivatisation was optimized: derivatisation time, temperature and volume of BSTFA added were studied. The best conditions were 20 min, 70oC and 50 μL of BSTFA respectively. Using the developed methodology, calibration curves were obtained for the 7 analytes (8 concentration points and four independent repetitions for each point). Linearity was found satisfactory (R2 ranged from 0.972 to 0.999). Within day repeatability (RSD less than 15%) was found very satisfactory. Stability of the derivatised sample was found limited to 48 hours. The limit of detection was found in the low ng/mg range (up to 0.5 ng/mg of hairs). The method was successfully applied to the analysis of samples from drug users.

Conclusion: A simple and efficient method was developed and validated for the detection and quantitation of amphetamines and cocaine and their metabolites in trace levels in hair. This tool is complementary to the existing arsenal of analytical tools in the fight against drug abuse, increasing the time span for the detection of drugs of abuse in biological samples.