Enhanced urinary stability of peptide hormones and growth factors by dried urine microsampling.

Volumetric absorptive microsampling (VAMS) and dried urine spot (DUS) strategies were applied for the collection of dried microsamples for anti-doping testing of low-stability peptide hormones and growth factors prohibited by the World Anti-Doping Agency (WADA). Drying, storage and transport conditions, as well as pretreatment steps, were optimised before liquid chromatography - tandem mass spectrometry (LC-MS/MS) analysis. The analytical method has been fully validated in terms of sensitivity (limits of quantitation 0.3-10 ng/mL), precision (RSD% < 6.6 %) and extraction yields (78-91 %). Dried microsample stability studies (90 days) have been performed and compared to fluid urine stability. Significantly higher losses have been observed in fluid urine stored at -20 °C (up to 55 %) and -80 °C (up to 29 %) than in dried urine microsamples stored at room temperature (< 19 %). The final microsampling and analysis protocols allow the collection of urine microvolumes, unlikely to be tampered, stably storable and shippable with no particular precautions for possible anti-doping testing of prohibited peptides and hormones.