Urine drug testing to support pain management is a mainstay of the clinical toxicology laboratory. Reduced reimbursement has continued to put increasing pressure on laboratories. Many toxicology labs are moving to larger drug panels to increase throughput and efficiency, while reducing turn-around-time and cost. Methods using LC-MS with 50 or more drugs and metabolites are increasingly common. These panels increase throughout and improve laboratory efficiency, but create many challenges. While “dilute and shoot” methods are easy and affordable, they can result in shortened LC column lifetimes and increased MS instrumentation downtime. Matrix effects can also effect sensitivity and overall method performance. Supported Liquid extraction (SLE) and Solid Phase Extraction (SPE) provide cleaner samples for LC-MS/MS and more robust clinical assays. Successful sample preparation method development requires understanding the retention mechanism of the analytes in the assay. The octanol-water partition coefficient (logP) and acid dissociation constant (pKa) of the compounds of interest are important properties that can guide sample preparation strategy and optimization of method conditions.
Literature number: P165.V.1