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

• Urine microsamples are obtained by dried urine spot (DUS) and volumetric absorptive microsampling (VAMS). • Doping-relevant peptide hormones and growth factors are analysed by an original LC–MS/MS methodology. • Detailed microsample stability is assessed and compared to fluid urine stability. • Enhanced peptide stability in dried microsamples is demonstrated. • Promising results demonstrate potential applicability to anti-doping testing of prohibited peptides and hormones. 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. [ABSTRACT FROM AUTHOR]