Determination of opiates in hair. Effects of extraction methods on recovery and on stability of analytes.

In order to evaluate (i) the recovery of extraction of opiates from authentic hair samples and (ii) the extent of hydrolysis of acetylated opiates (6-acetylmorphine, acetylcodeine) occurring during sample preparation, three different methods of extraction commonly used for opiates have been compared. To this purpose a sample consisting of a pool of hair collected from several heroin overdose cases has been submitted alternately to (A) digestion in 2 M NaOH at 80 degrees C for 1 h (n = 5), (B) incubation in 0.1 M HCl at 45 degrees C for 18 h (n = 5) and (C) incubation in methanol at 37 degrees C for 18 h (n = 5). After pH adjustment of the different incubation media to 7-8, analytes have been isolated by means of SPE using Bond Elut certify columns and derivatized with MSTFA. Analyses have been performed by either GC-MS in the selected ion monitoring mode or, omitting SPE, by radioimmunoassay. The extent of hydrolysis of 6-acetylmorphine to morphine and of acetylcodeine to codeine have been determined by submitting blank hair samples spiked with the acetylated analytes to the different extraction methods and measuring the amount of morphine and codeine formed. Both the recovery of extraction of the total morphine fraction (6-acetylmorphine + morphine) and the rate of hydrolysis of 6-acetylmorphine were found to be in the order: A > B > C. Similar results were obtained for the total codeine fraction (acetylcodeine + codeine). These results clearly indicate that: (i) the concentration of opiates measured in hair depends on the extraction method used; (ii) ratios between different analytes (e.g. 6-acetylmorphine vs. morphine) may reflect the rate of hydrolysis during sample preparation rather than different types of exposure to opiates.