Direct tandem mass spectrometry for the simultaneous assay of opioids, cocaine and metabolites in dried urine spots

A micro-analytical method based on spotting urine samples (20 mu L) onto blood/urine spot collection cards followed by air-drying and extraction (dried urine spot, DUS) was developed and validated for the screening/confirmation assay of morphine, 6-methylacetylmorphine (6-MAM), codeine, cocaine and benzoylecgonine (BZE). Acetonitrile (3 mL) was found to be a useful solvent for target extraction from DUSs under an orbital-horizontal stirring at 180 rpm for 10 min. Determinations were performed by direct electrospray ionization tandem mass spectrometry (ESI-MS/MS) under positive electrospray ionization conditions, and by using multiple reaction monitoring (MRM) with one precursor ion/product ion transition for the identification and quantification (deuterated analogs of each target as internal standards) of each analyte. The limits of detection of the method were 0.26, 0.94, 1.5, 1.1, and 2.0 ng mL(-1), for cocaine, BZE, codeine, morphine and 6-MAM, respectively; whereas, relative standard deviations of intra- and inter-day precision were lower than 8 and 11%, respectively, and intra- and inter-day analytical recoveries ranged from 94 +/- 4 to 105 +/- 3%. The small volume of urine required (20 mu L), combined with the simplicity of the analytical technique makes it a useful procedure for screening/quantifying drugs of abuse. The method was successfully applied to the analysis of urine from polydrug abusers. (C) 2013 Elsevier B.V. All rights reserved.