Application of High-Resolution UPLC-MSE/TOF Confirmation in Forensic Urine Drug Screening by UPLC-MS/MS

The transition from presumptive (immunoassay) drug screening to definitive screening has continued in the practice of analytical toxicology. Development of a ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) screening method for over sixty drugs and metabolites (analytes) in urine has been reported by the authors and has been applied in probation, drug court, social services, chemical dependency, pain management and addiction medicine casework. Testing by the definitive screening method has increased both the rate and diversity of initial-positive drug findings, due to the lower positive thresholds and wider panel of analytes. Use of definitive screening in forensic casework, however, requires retesting of initial-positive analytes using a second method based upon a different analytical technique with at least equivalent sensitivity and selectivity. Consequently, a UPLC-MSE/TOF method for confirmation of the initial-positive analytes has been adapted; the method is for targeted confirmation and is based upon an alternate mass spectrometry technology and column separation. Both the initial screen and the confirmatory analysis employ threshold accurate calibration for normalization of matrix effects, without the use of stable isotopes. Validation and application of the complete workflow, in forensic urine drug testing casework, is reported.