A Rapid Sample Preparation for Quantitative Analysis of Cortisol in Saliva and Urine by LC-MS/MS

Summary of MSACL 2015 Poster Presentation by: Daniel Zhou and Run-Zhang Shi, Clinical Chemistry and Immunology of Clinical Laboratories, Stanford Health Care

Reduce manual sample preparation time

For determining saliva and urine cortisol levels LC-MS/MS is the measurement method of choice with high sensitivity and specificity. However, the conventional LC-MS/MS approach requires lengthy manual sample preparation by liquid-liquid extraction [LLE] or solid phase extraction [SPE], and patient samples are processed in a batch mode. To shorten sample preparation time, Stanford investigated dispersive pipette XTRaction tips that contained weak anion exchange (WAX) sorbent and salt (S) necessary for SALLE (Salting-out Assisted Liquid-Liquid Extraction) as a quick alternative. Stanford validated this improved LC-MS/MS method in a clinical chemistry laboratory. Assay characteristics such as sensitivity, specificity, linearity, and precision are presented. We conclude that the improved LC-MS/MS method is rapid and as sensitive as the conventional LC-MS/MS approach making it much more suitable for clinical diagnostic use.

PretreatmentAdd 50 μL internal standard and 500 μL acetonitrile to 250 μL of patient saliva and urine samples. Vortex and incubate at room temperature for 10 minutes
ExtractionAspirate and Dispense 3x with WAX-S-XTR tips
ElutionTransfer 300 μL organic upper layer
Prep for injectionSolvent evaporate and reconstitute in 120 μL of H2O/MeOH

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