Detection of “smoke powder” etomidate and its metabolite etomidate acid in blood and urine by UHPLC–MS-MS: application in authentic cases

Recently, etomidate has been widely used as an alternative in illicit drug market. It is usually added to regular cigarette tobacco (commonly known as "cigarette powder") or mixed in e-cigarette oil sold through the Internet, retail stores, or entertainment outlets and other channels. An ultra-high performance liquid chromatography tandem mass spectrometry method was developed to quantify etomidate and etomidate acid in human blood and urine. The limit of detection (LOD) of etomidate and etomidate acid in blood is 0.5 and 2 ng/mL, respectively, and the lower limit of quantification (LLOQ) is 1 and 5 ng/mL, respectively. The LOD of etomidate and etomidate acid in urine is 1 and 2 ng/mL, respectively, and the LLOQ is 2 and 5 ng/mL, respectively. The precision, accuracy, recoveries, and matrix effects of etomidate and etomidate acid determinations in blood and urine met the requirements for methodological validation. The method was successfully applied to the identification and quantification of etomidate and etomidate acid in blood and urine of 62 forensic cases. The concentration of etomidate ranged from 1.52 to 8.41 ng/mL (positive cases, n = 5) and the concentration of etomidate acid ranged from 2.76 to 112 ng/mL (positive cases, n = 5) in blood. The concentrations of etomidate and etomidate acid in urine samples were 2.64-79,300 ng/mL (positive cases, n = 59) and 6.11-518,000 ng/mL (positive cases, n = 60), respectively. Therefore, the concentration of etomidate in blood and urine is mostly higher than that of etomidate.