Rapid qualitative and quantitative analysis of etomidate and its structural analogs in blood by UPLC-MS/MS and application in six forensic cases.

Etomidate and its structural analogs have been increasingly abused, posing significant risks to public safety. This study aimed to develop an ultra-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantification of etomidate, metomidate, isopropoxate, propoxate, and etomidate acid in human blood. The method involved taking 1 mL of a blank blood sample, adding 3 µL of 100 ng/mL internal standard solution and 3 mL of diethyl ether, vortexing, centrifuging, and then drying and redissolving the supernatant for analysis. The correlation coefficient (r) values of the calibration curves for etomidate and its structural analogs in blood samples in the range of 0.1-10 ng/mL and etomidate acid in the range of 1-100 ng/mL were all greater than 0.999. The limit of detection (LOD) and limit of quantitation (LOQ) of etomidate and its structural analogs were 0.05 ng/mL and 0.1 ng/mL, respectively. The LOD and LOQ of etomidate acid were 0.5 ng/mL and 1 ng/mL, respectively. Precision, accuracy, recovery, matrix effect, and dilution integrity met the validation requirements. The method for quantitative analysis of etomidate and its structural analogs in blood samples was established and validated, enabling the separation of the isomers propoxate and isopropoxate. In addition, the method was successfully applied to six real blood samples in forensic cases.