Liquid–liquid extraction solvent selection for comparing illegal drugs in whole blood and dried blood spot with LC–MS–MS

This study focused on the simultaneous detection of amphetamine, 3,4-methylenedioxy methamphetamine, morphine, benzoylecgonine, and 11-nor-9-carboxy-tetrahydrocannabinol in whole blood and dried blood spot (DBS). It is aimed to select a solvent mixture for liquid-liquid extraction technique employing liquid chromatography-tandem mass spectrometry (LC-MS-MS). The obtained DBS results were compared with the whole blood samples results. A simple, rapid, and reliable LC-MS-MS method was developed and validated for all analytes in whole blood and DBS. LC was performed on a Hypersil Gold C18 column with an initial gradient of 0.01% formic acid, 5 mM ammonium format buffer in water, and acetonitrile at 0.3 ml/min with 7.5 min runtime. A methanol:acetonitrile (40:60 v/v) mixture was selected for both matrices. Limit of quantitation (LOQ) values were 10-25 ng/mL; linear ranges were LOQ-500 ng/ml for all analytes; correlation coefficients were greater than 0.99, and all calibrator concentrations were within 20%. Analytical recovery in blood and DBS ranged from 84.9% to 113.2% of the expected concentration for both intra- and inter-day. Analytes were stable for 1, 10, and 30 days after three freeze/thaw cycles. It was determined that the variances of the results obtained with the two matrices in the comparison study were equal for each analyte, and the results were highly correlated (r = 0.9625). A sensitive, accurate, and reliable chromatographic method was developed to determine amphetamine, 3,4-methylenedioxy methamphetamine, morphine, benzoylecgonine, and cannabis, by performing the same preliminary steps with whole blood and dried blood spots. It was observed that the results obtained in these two matrices were compatible and interchangeable when statistically compared.