Determination of morphine and codeine in blood and bile by gas chromatography with a derivatization procedure

Two gas chromatographic methods for the simultaneous quantitation of morphine and codeine in blood and bile from cases of opiate-related deaths are described. Both methods employ simple solvent extraction followed by hexane-ethanol partitioning clean-up and use nalorphine as the internal standard. The first method relies on the formation of trimethylsilyl derivatives and detection with a nitrogen-phosphorous detector. The second method involves the formation of heptafluorobutyryl derivatives and detection with an electron capture detector. Both methods are sensitive, able to detect down to 0.04 microgram/mL of morphine and 0.1 microgram/mL of codeine. Their wide linear dynamic ranges cover from low therapeutic to lethal levels for both morphine and codeine. The methods are amenable to batchwise operation and each analysis can be completed within three hours. The results of both methods correlate very well. The trimethylsilyl derivatives can be hydrolyzed and rederivatized for form heptafluorobutyryl derivatives for the second method, which then serves to confirm the results of the first method. Pholcodine, another common opiate, can likewise be determined. Average recovery was 80% for blood morphine and codeine and 60% for bile morphine and codeine.