Hair analysis by infrared microscopy for drugs of abuse

Hair analysis overcomes many of the drug testing problems associated with urinalysis. However, hair analysis has its own unique problem in that passive contamination of the exterior surface of the hair can taint the analysis with false positive. Infrared microscopy can examine the interior of the hair and differentiate passive contamination from drugs absorbed into the hair from ingestion. By microtoming the hair either cross-sectionally or laterally, infrared spectra can be obtained of the cortex and medulla of a single hair with a nominal spatial resolution of 10 microns. Three dimensional infrared imaging is possible with Fourier transform infrared (FT-IR) microscopy and yields a plot that can be understood by the layman.