As the use of prescription and nonprescription drugs grows, the need for fast, accurate, and comprehensive methods is also rapidly increasing. Historically, drug testing has focused on forensic applications such as cause of death determinations or the detection of drug use in specific populations (military, workplace, probation/parole, sports doping). However, modern drug testing has expanded well into the clinical arena with a growing list of target analytes and testing purposes. Clinicians often request the analysis of large panels of drugs and metabolites that can be used to ensure compliance with prescribed pain medication regimens and to detect abuse or diversion of medications. With prescription drug abuse reaching epidemic levels [1], demand is growing for analytical methods that can ensure accurate results for comprehensive drug lists with reasonable analysis times. LC-MS/MS is an excellent technique for this work because it offers greater sensitivity and specificity than immunoassay and—with a highly selective and retentive Raptor™ Biphenyl column—can provide definitive results for a wide range of compounds.
Typically, forensic and pain management drug testing consists of an initial screening analysis, which is qualitative, quick, and requires only minimal sample preparation. Samples that test positive during screening are then subjected to a quantitative confirmatory analysis. Whereas screening assays may cover a broad list of compounds and are generally less sensitive and specific, confirmation testing provides fast, targeted analysis using chromatographic conditions that are optimized for specific panels. C18 columns are commonly used and generally work well for hydrophobic compounds that separate using dispersive retention. However, not all compounds exhibit this type of interaction and many of today’s complex mixtures and difficult matrices require more advanced retention mechanisms. Raptor™ Biphenyl columns exploit the pi-pi (π ‐π) interactions of fused ring compounds with substituted electron withdrawing groups that are typical of many medications, which results in improved retention for a wider range of structurally diverse drugs and metabolites. The Raptor™ Biphenyl column was used to develop LC-MS/MS methodology for 231 drugs and drug metabolites because it has the retention required for the wide range of compound classes tested here. It also provides improved selectivity for over 40 structurally similar drugs and metabolites, even those not normally resolved by a C18 column. The comprehensive analysis of 231 compounds shown in this article demonstrates the power and utility of the Raptor™ Biphenyl column for developing multiclass screening assays. Further, the panel-specific confirmation methods discussed later in the article can be paired either with an LC-MS/MS screening method or with traditional immunoassay screening tests. Note that stability experiments and validation in matrix should be performed to demonstrate effectiveness and reproducibility prior to implementing any method for actual sample analysis.
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