Evaluation of a solid-phase extraction procedure for the simultaneous determination of morphine, 6-monoacetylmorphine, codeine and dihydrocodeine in plasma and whole blood by GC/MS.

Different procedures of solid-phase extraction were re-examined and a new solid-phase extraction procedure was developed using gas chromatography-mass spectrometry for the simultaneous detection and quantitation of morphine, 6-monoacetylmorphine, codeine and dihydrocodeine in plasma and whole blood. The effects of different types of sorbent and buffer solutions on the recoveries and purity of the extracts were also studied. Some preparation techniques on whole blood samples were also investigated. The method developed using Chromabond C18 (100) with spiked plasma samples had good recoveries for all opiates of interest: morphine 93.1% +/- 7.4%, 6-monoacetylmorphine 68.0% +/- 6.7%, codeine 77.0% +/- 8.3% and dihydrocodeine 67.9% +/- 8.4%. The detection limit of all compounds was less than 5 micrograms/L. The blank plasma showed no interfering peaks in the GC/MS-analysis.