GC-MS Determination of Opiates in Saliva with Small Volume Liquid Extraction

Opiates (i.e., morphine, 6-monoacetylmorphine and codeine) in saliva were determined by GC-MS with small volume liquid extraction. In a phosphate buffer solution of pH 9, 1 mL of soliva sample was extracted ultrasonically with 150 μL of chloroform for 10 min. After centrifugation, 80 μL of the supernatant liquid was taken and derivatized with the reagent N-methyl-bis-trifluoroacetamide, and the derivitized product in the solution was determined by GC-MS. Values of detection limit (3S/N) found for the 3 opiates mentioned above were 0.005, 0.003, 0.002 mg·L-1 respectively. Ethyl morphine was used as internal standard. Ranges of linearity of calibration curves for the 3 opiates were same in the range of 0.01-1.0 mg·L-1. Recovery and precision of the method were tested by addition of mixed opiate standard at 3 concentration levels, giving values of recovery in the ranges of 38.1%-50.0% (for morphine), 81.5%-88.8% (for 6-monoacetylmorphine) and 89.9%-109.8% (for codeine); with values of RSD′s (n=5) in the range of 6.7%-18.4%.