Laboratory of Clinical Toxicology, C.H.U. de Liège, B-4000 Sart Tilman, Belgium

With morphine and codeine as model compounds, all solvents volumes and flows were optimized on a C18 SPE column leading to recoveries of nearly 100%. Final analysis involved GC-MS after derivatization with trifluoroacetic anhydride (TFAA).

Using selected ion monitoring (SIM) and deuterated morphine as internal standard, limit of detection (LOD) of 7 ng/ml and limit of quantitation (LOQ) of 8.5 ng/ml were achieved for both compounds. Linearity was good from the LOQ up to 20,000 ng/ml. At 200 ng/ml, intra- and inter-day variabilities were respectively 0.5 and 2.2 % for morphine and 6.1% and 8.8 % for codeine. These results highlight the need of deuterated codeine for a better reproducibility of these analysis. The same method was found to be suitable for plasma samples.