The Use of Molecular Weight Cut-off Filters to Reduce Ion Suppression in the Analysis of Cocaine in Hair

摘要

Cocaine-N-oxide (CNO) is a cocaine (COC) metabolite and is likely to be incorporated into cocaine users' hair. Other cocaine metabolites often measured in biological fluids or tissues have shown to be either potential impurities or degradation products making the determination of ingestion difficult. Hair samples provide a test for long-term exposure/ingestion (weeks to months) as compared to conventional biological matrices used. A validated method for hair analysis has not yet been developed for cocaine exposure. One of the challenges in working with complex biological samples is dealing with ion suppression during the ionization process. Suppression is attributed to the hair matrix, which competes for ionization with target cocaine metabolites. The work presented here demonstrates preliminary results for method development using liquid chromatography/mass spectrometry (LC/MS) for the detection of CNO in hair with the overall hypothesis to determine if cocaine findings from hair are due to environmental exposure or ingestion. A variety of human hair samples were analyzed to study how to reduce the effects of hair matrices on CNO response. Experimental variables such as washing the hair prior to extraction (n(velence)6), filter selection (n(velence)4), and solid phase extraction (SPE) (n(velence)4) were examined to increase the response of CNO in hair extracts.