Influence of sample preparation on analytical results: drug analysis [GC/MS] on hair snippets versus hair powder...

The comparison of aqueous extraction methods and hair extraction by organic solvents performed on hair powder as well as on hair snippets of the same sample revealed different qualities of the procedures. Qualitative and quantitative results by the same derivatization step and GC/MS detection demonstrated, that the risk of missing a drug substance is higher using hair snippets than after drug extraction on pulverised hair. Drug recovery for opiates, cocaine and benzoylecgonine from hair was found to be best in aqueous solvents or in methanol extracts. The results are discussed under the aspects of solid-phase extraction, the hair sample representing an inhomogenous material. The localisation of drug molecules in hair, the hair swelling and penetration behavior of the particular extraction medium as well as the partition coefficient of solvent/hair phase for a particular drug substance are considered to influence the results.