Evaluation of extraction techniques for the forensic analysis of human scalp hair using gas chromatography/mass spectrometry (GC/MS)

Preliminary research using on-line supercritical fluid extraction/gas chromatography-mass spectrometry (SFE/GC-MS) has shown that the natural and artificial surface components of human scalp hair are reproducible and differentiable. Therefore, these components may be useful for individualization or determining demographic characteristics or both. However, it is not known how the efficiency and selectivity of on-line SFE/GC-MS compares to other extraction methods. In this study, ultrasound, Soxhlet, and pressurized-fluid extraction were used to extract 1 mg to 1.3 g portions of a composite hair sample taken from an Asian male between the ages of 10 and 18. Percent extractables ranged from 0.9% to 5.6%, depending on the solvent used, and tended to increase with solvent polarity. Chemical analysis using GC/MS showed that the extracts contained large proportions of free fatty acids, squalene, cholesterol, and various wax esters. Finally, comparisons to SFE/GC-MS showed that this method possesses adequate efficiency, no observable differences in selectivity, and greater potential for miniaturization.