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.
Pretreatment | Add 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 |
Extraction | Aspirate and Dispense 3x with WAX-S-XTR tips |
Elution | Transfer 300 μL organic upper layer |
Prep for injection | Solvent evaporate and reconstitute in 120 μL of H2O/MeOH |
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