Determination of Etomidate and Its Metabolite in Hair and Urine by HPLC-MS/MS

A method was developed for the determination of etomidate and its metabolite etomidate acid in hair and urine by high performance liquid chromatography-triple quadrupole tandem mass spectrometer (HPLC-MS/MS). The hair samples were ground and extracted by ultrasonic extraction with methanol. After protein was precipitated by acetonitrile, the urine samples were centrifuged at high speed and passed through 0.22 μm filter membrane, and then Agilent Eclipse Plus C18 RRHD (3.0 mm×150 mm×1.8 μm) column was used for analysis. Gradient elution was performed with 0.1% formic acid aqueous solution-acetonitrile as mobile phase at the flow rate of 0.5 mL/min. Electrospray ion source and multiple reaction monitoring (MRM) positive ion mode were selected. The results showed that the linear relationship of the two compounds exhibited good linearity in the concentration range of 0.5 to 50 ng/mL in urine and 0.025 to 2.5 ng/mg in hair, and the R² value was greater than 0.9925. The extraction recoveries ranged from 91.0% to 107.5%, and the intra-day and inter-day precision RSD was 0.4% to 7.4%, while the intra-day and inter-day accuracy was 91.5% to 110.8%. In the actual cases, six hair samples and 4 urine samples were tested, and the test results showed that etomidate was detected in all six hair samples, and the metabolite etomidate acid was detected in two hair samples, but the concentration was much lower than the original. Etomidate and metabolite etomidate acid were detected in two urine samples, and the metabolite concentration was much higher than the original. In conclusion, this method can be used for rapid qualitative and quantitative analysis of etomidate and its metabolite in the hair and urine of etomidate users.