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Urine sample Isolute SLE+

Sample Preparation Strategies for Urine Panels with 50 Drugs

02 October 2017

Many toxicology labs are moving to larger drug panels to increase throughput and reduce turn-around-time and cost. Methods using LC-MS with 50 or more drugs and metabolites are increasingly common, but create many challenges.

 

A poster (P165) presented at ASMS 2017, Indianapolis, discusses three sample preparation methodologies for 52 drug analytes, and presents evaluations of recovery, matrix effects and process efficiency. 

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.

Conclusions

  • Supported liquid extraction and mixed-mode SPE worked best for the most compounds
  • Compromises in recovery and sample cleanliness are necessary with large drug panels in urine that have analytes with very different properties
  • Knowing the logP and pKa of your compounds is essential for successful method development

Download the poster below.