A Novel Method for the Detection of Cocaine in Hair using a Freeze/ Thaw Method and GC/ MS Analysis

M. L. Schmidt, L. Quarino,

Abstract: In order to create an efficient and less strenuous method for the detection of cocaine in hair, a simple freezethaw extraction method was developed and coupled to gas chromatography/mass spectrometry (GC/MS). GC/MS analysis parameters were determined by testing solutions of cocaine and two of its metabolites, cocaethylene and ecgonine methyl ester. Ions from these compounds and two pyrolysis products, anhydroecgonine methyl ester and 3-ethoxy-4-methoxyphenethylamine, were chosen in order to test samples using selected ion monitoring (SIM). The qualitative limit of detection for anhydroecgonine methyl ester, 3-ethoxy-4-methoxyphenethylamine, ecgonine methyl ester, cocaine, and cocaethylene were 0.1, 0.1, 0.50, 0.05, and 0.05 ng, respectively. Using cocaine-positive hair samples from Willow Laboratories (Lynn, MA, USA), an extraction method was developed where tested hairs were washed, segmented, covered in acetonitrile, frozen and thawed for five cycles, and evaporated until a minimal amount of liquid remained. Results were obtained with 2ul of extract using GC/MS with SIM. Ions specific for cocaine were identified in the cocaine-positive hair samples, allowing for cocaine-positive hairs to be distinguished from cocainenegative hair samples. Utilizing this method, results can be obtained with as little as 10mg of hair, though 20mg is recommended. A blind testing study with samples from Willow Laboratories provided results that were consistent with those obtained by other methodologies employed by Willow Laboratories. Thus, the freeze/thaw method via GC/MS analysis is a viable method that significantly decreases sample preparation by improving upon the ease of extraction for the detection of cocaine in hair.
Keywords: Hair, Cocaine, Extraction;, Freeze/thaw, Gas chromatography/mass spectrometry