Analysis of drug panels in urine samples can be challenging, and the trend towards larger panels including multiple drug classes compounds the issues faced during method development.
This white paper examines a number of aspects of sample preparation, and their impact on the success of subsequent LC-MS/MS analysis of broad urine panels.
Section 1 examines the applicability of various sample preparation techniques: supported liquid extraction, reverse phase SPE and mixed-mode SPE, to the various classes of drugs extracted. In addition, hydrolysis approaches: enzyme type and protocol used (time, temperature), are compared.
Mixed-mode reverse phase/cation exchange SPE is widely used for extraction of basic drug classes from urine, but the inclusion of drugs and metabolites that exhibit ‘non-typical’ functionality within urine panels can be problematic. Section 2 examines the impact of various parameters (interference wash strength, elution solvent composition) on analyte retention, elution and extract cleanliness with particular focus on zwitterionic (gabapentin, pregabalin) and non-ionic (carisoprodol, meprobamate) drugs.