Identification and quantification of synthetic cathinones in blood and urine using liquid chromatography-quadrupole/time of flight (LC-Q/TOF) mass spectrometry

Synthetic cathinones continue to present a formidable challenge to forensic toxicology laboratories despite the fact that they are often encountered in impaired driving and death investigations. Due to limitations in immunoassay-based screening technologies, many forensic toxicology laboratories must rely on more labor intensive chromatographic-based screening approaches in order to detect these drugs in biological evidence. Solid phase extraction (SPE) and liquid chromatography-quadrupole/time of flight (LC-Q/TOF) mass spectrometry were used to identify twenty-two synthetic cathinones in urine and blood. Target drugs included methcathinone, ethcathinone, pentedrone, buphedrone, 3-fluoromethcathinone (3-FMC), 4-fluoromethcathinone (4-FMC), 4-methylethcathinone (4-MEC), 4-ethylmethcathinone (4-EMC), mephedrone, methedrone, 3,4-dimethylmethcathinone (3,4-DMMC), ethylone, butylone, pentylone, eutylone, methylone, methylenedioxypyrovalerone (MDPV), 4-methylpyrrolidinobutiophenone (MPBP), 3,4-methylenedioxypyrrolidinobutiophenone (MDPBP), α-pyrrolidinopentiphenone (α-PVP), pyrovalerone, and naphyrone. A total of nine deuterated internal standards were employed. Using traditional reversed phase chromatography all positional isomers, including 3-FMC and 4-FMC, were separated in 12 min. The procedure was validated in accordance with the Scientific Working Group for Forensic Toxicology (SWGTOX) Standard Practices for Method Validation. Extraction efficiencies were 84-104% and 81-93% in urine and blood, respectively. Limits of quantitation in both matrices were 0.25-5 ng/mL. Precision, bias and matrix effect were all within acceptable thresholds and the assay was free from more than fifty interferences. The validated method was used to identify cathinones in authentic urine case samples (n = 20) and these results highlight important considerations for cathinone stability and the subsequent interpretation of results.