Improved solid-phase extraction of methadone and its two major metabolites from whole blood

A solid-phase extraction (SPE) method for the efficient extraction of methadone and its two major metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine and 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline, from whole blood is described. The procedure combines extraction on Isolute™ Confirm HCX mixed-mode SPE columns and gas chromatographic-mass spectrometric analysis with deuterated methadone as the internal standard. The optimum extraction conditions for all three analytes were determined using spiked whole blood. The developed method is easier and faster than current liquid–liquid extraction (LLE) procedures and produces cleaner extracts. Calibration curves were linear from 0 to 600 ng/mL (r² > 0.99) with recoveries greater than 90% for all three analytes. The concentrations of methadone and its metabolites in postmortem blood were determined in fatal cases using the developed SPE method and were found to compare well with results obtained using LLE