Determining morphine in biologic fluids of rats by gas chromatography–mass spectrometry

This study describes a sensitivity and selectivity approach based on gas chromatography–mass spectrometry to determinate morphine levels in rat biologic fluids. Optimized experimental conditions of solid-phase extraction (SPE), including pH of the sample, solvent composition, and various sorbents, are examined herein. The largest recovery is greater than 94.0% for morphine, is achieved with a mixed sorbent C8/SCX and mixed elution CHCl3/iso-propanol (9:1) at pH 6.8. Acetylation accomplished with acetic anhydride is utilized to derivatize morphine to 3,6-diacetylmorphine for GC/MS analysis. The proposed method was precise and a wide linear range from 0.5 to 500 ng mL−1. A detection limit of 0.31 ng mL−1 in urine is achieved. The maximum ratio of morphine glucuronide to morphine in the blood of rat is 6 to 1. A terminal half-life of morphine in blood is calculated as around 120 min.