Detection of Cathinone and Mephedrone in Plasma by LC-MS/MS Using Standard Addition Quantification Technique

Designer drugs are structural analogs of Drug Enforcement Agency (DEA) Schedule I and II substances. They are synthesized to mimic the effects of illegal drugs of abuse and to bypass the provisions of drug regulations. Despite the increased availability of designer drugs, few studies have focused on specific analytical extraction techniques for their detection and quantification in biological samples. Solid phase extraction (SPE) is the most commonly used technique for sample preparation. The purpose of this study is to evaluate the extraction efficiency of the various SPE columns with different sorbent materials for two designer drugs, cathinone and mephedrone in sheep plasma using LC-MS/MS as well as to evaluate the standard addition quantification technique. SPE columns used in this study were Phenomenex Strata X-C strong cation mixed mode column, Phenomenex Strata X Drug B strong cation mixed mode column and SupelTM HLB hydrophilic modified styrene polymer column. The Phenomenex Strata X-Drug B strong cation cartridge was found to have the best retention profile for our analytes. Percent recovery of initial cathinone concentration was 137.6, 93.6 and 103.6% for 10, 33 and 100ng/mL cathinone respectively using the standard addition method with the X-intercept and 120.9, 91.1 and 103.2% with calculations based on the Y-intercept. Percent recovery of initial mephedrone concentration was 191.9, 105.7 and 116.7% for 10, 33 and 100ng/mL mephedrone respectively using the standard addition method with the X-intercept and 153.5, 97.1 and 115.1% using the Y-intercept