Detection of Etomidate and Etomidate Acid in Urine Using HPLC-MS/MS Method

To establish a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the detection of etomidate and etomidate acid in urine samples.

Protein in the urine samples was precipitated by adding acetonitrile, and the supernatant was obtained after centrifugation and filtered. The supernatant was separated on a C₁₈ column with a mobile phase consisting of 0.1% formic acid solution and acetonitrile at a flow rate of 0.4 mL/min. The detection was performed in positive electrospray ionization (ESI) and multiple reaction monitoring (MRM) modes. The method was validated for selectivity, linearity and limit of detection (LOD), and applied to a case of etomidate poisoning death.

The LOD of etomidate and etomidate acid were 0.2 and 0.5 ng/mL, respectively, and the limit of quantitation (LOQ) were 0.5 and 1.0 ng/mL, respectively. Good linear relationship was observed within the linear range (r>0.995 0). At three concentration levels (0.5, 5, 50 ng/mL for etomidate and 1, 10, 100 ng/mL for etomidate acid), the matrix effect was within the range of 5.42% to 18.47%, the extraction recovery rate was greater than 84.25% and the stability was greater than 88.23%. The accuracy, precision and dilution reliability all met the experimental requirements. Etomidate and etomidate acid were successfully detected with the concentrations of 8.82 and 27.88 μg/mL in the urine of a deceased individual who had consumed excessive etomidate.

The method has simple pretreatment, high sensitivity and wide linear range, which can be applied to the detection of etomidate and etomidate acid in urine samples in forensic science.