Determination of cathinones and related ephedrines in forensic whole-blood samples by liquid-chromatography–electrospray tandem mass spectrometry

A liquid-chromatography-tandem-mass-spectrometry method using pneumatically assisted electrospray ionisation (LC-ESI-MS/MS) was developed for the simultaneous determination of cathinone, methcathinone, ethcathinone, amfepramone, mephedrone, flephedrone, methedrone, methylone, butylone, cathine, norephedrine, ephedrine, pseudoephedrine, methylephedrine and methylpseudoephedrine in human live and post-mortem whole blood. The blood proteins were precipitated by the addition of methanol, and the extract was purified by ultrafiltration. The separation of diastereomeric ephedrines was achieved on an ethyl-linked phenyl column. Matrix-matched calibrants combined with the isotope dilution of selected substances were used for quantitative analysis. The relative intra-laboratory reproducibility standard deviations were generally better than 7% at concentrations of 20 μg/L, and the mean true recoveries were 87-106% in the concentration range of 10-250 μg/L. The detection limits were in the range of 0.5-3 μg/L. The cathinones were unstable in whole blood and sample extracts under neutral conditions, but the stability could be improved by the acidification of the sample matrix.