LC-MS/MS and volumetric absorptive microsampling for quantitative bioanalysis of cathinone analogues in dried urine, plasma and oral fluid samples

In the last few years, several cathinone analogues have appeared on the illicit drug market and proposed as an alternative to already known stimulants in several recreational settings. The World Anti-Doping Agency classified the synthetic cathinones in the Prohibited List as specified stimulants, banned in sport competitions. We developed and validated an LC-MS/MS method for the analysis of methylone, ethylone, butylone, mephedrone, 4-methylethcathinone and 3,4-methylenedioxypyrovalerone in dried urine, plasma and oral fluid samples. Volumetric absorptive microsampling has been employed as a miniaturised sampling technique for collecting dried biological samples. Chromatographic analysis was carried out on a C18 reversed phase column with a mobile phase composed of formic acid in a water/acetonitrile mixture, by using a triple quadrupole mass analyzer. The main parameters of the volumetric absorptive microsampling procedure were investigated and the method was fully validated with satisfactory results in terms of linearity, precision, absolute recovery, matrix effects, selectivity and stability. The method was successfully applied to real samples collected from cathinones users. The biosampling strategy via volumetric absorptive microsampling for urine, plasma and oral fluid could provide reliable information, with a future perspective of implementation for forensic cases as well as for sport drug testing.