Green analytical toxicology method for determination of synthetic cathinones in oral fluid samples by microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry.

Abstract

We developed and validated a method for quantitative analysis of ten synthetic cathinones in oral fluid (OF) samples, using microextraction by packed sorbent (MEPS) for sample preparation followed by liquid chromatography‒tandem mass spectrometry (LC‒MS/MS). OF samples were collected with a Quantisal™ device and 200 µL was extracted using a C18 MEPS cartridge installed on a semi-automated pipette and then analyzed using LC‒M/SMS. Linearity was achieved between 0.1 and 25ng/mL, with a limit of detection (LOD) of 0.05ng/mL and a limit of quantification (LOQ) of 0.1ng/mL. Imprecision (% relative standard deviation) and bias (%) were better than 11.6% and 7.5%, respectively. The method had good specificity and selectivity against 9 different blank OF samples (from different donors) and 68 pharmaceutical and drugs of abuse with concentrations varying between 400 and 10,000ng/mL. No evidence of carryover was observed. The analytes were stable after three freeze/thaw cycles and when kept in the autosampler (10°C) for up to 24h. The method was successfully applied to quantify 41 authentic positive samples. Methylone (mean 0.6ng/mL, median 0.2ng/mL), N-ethylpentylone (mean 16.7ng/mL, median 0.35ng/mL), eutylone (mean 39.1ng/mL, median 3.6ng/mL), mephedrone (mean 0.5ng/mL, median 0.5ng/mL), and 4-chloroethcathinone (8.1ng/mL) were quantified in these samples. MEPS was an efficient technique for Green Analytical Toxicology purposes, which required only 650 µL organic solvent and 200 µL sodium hydroxide, and the BIN cartridge had a lifespan of 100 sample extractions.