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.

Analysis of γ-hydroxy butyrate by combining capillary electrophoresis-indirect detection and wall dynamic coating: application to dried matrices.

γ-Hydroxybutyric acid (GHB) is a powerful central nervous system depressant, currently used in medicine for the treatment of narcolepsy and alcohol dependence. In recent years, it has gained popularity among illegal club drugs, mainly because of its euphoric effects as well as doping agent and date rape drug. The purpose of the present work was the development of a rapid analytical method for the analysis of GHB in innovative biological matrices, namely dried blood spots (DBSs) and dried urine spots (DUSs). The analytical method is based on capillary zone electrophoresis with indirect UV absorption detection at 210 nm and capillary wall dynamic coating. The background electrolyte is composed of a phosphate buffer containing nicotinic acid (probe for detection) and cetyltrimethylammonium bromide (CTAB, reversal of electroosmosis in wall dynamic coating). The influence of probe and CTAB concentration, together with buffer pH, on migration time and signal response was investigated. Under the optimized conditions, analytical linearity and precision were satisfactory; absolute recovery values were also high (>90 %); the use of dried matrices (DBSs and DUSs) was advantageous as an alternative matrix to classical ones. No interferences were found either from the most common exogenous or from endogenous compounds. This analytical approach can offer a rapid, precise and accurate method for GHB determination in innovative biological samples, which could be important for screening purposes in clinical and forensic toxicology. Graphical Abstract CE method, by combined indirect UV detection and dynamic coating, for GHB determination in DBSs and DUSs.