Multi-analyte screening of small peptides by alkaline pre-activated solid phase extraction coupled with liquid chromatography-high resolution mass spectrometry in doping controls

Peptidic drugs with wide spectrum of physiological activity are of interest for cheating athletes and can be misused as doping in sports. A growing number of small peptide drugs capable of enhancing performance are included in the prohibited list issued by World Anti-Doping Agency (WADA), therefore the improvement of the detection methods is constantly needed. In the present study, a screening assay was developed comprising 54 prohibited small peptides and the related substances in urine by means of the alkaline pre-activated weak cation exchange-solid phase extraction (WCX-SPE) with liquid chromatography-high resolution mass spectrometry (LCHRMS). This method performed good enrichment and purification effect of traditional WCX for basic peptides, and also improve the purification power of acidic peptides, which significantly expanded the coverage of detection substances. The method was validated in accordance with WADA relevant criteria and validated with a main focus on qualitative parameters including selectivity, limits of detection (0.02-0.2 ng/mL), linearity (0.1-20 ng/mL for 46 analytes and 0.2-20 ng/mL for 9 analytes), accuracy and precision (RE% and RSD% < 20% at 1, 5 and 10 ng/mL), recovery (39.2%-100.1% except for the TB500(1-2) free acid: 9.2%), matrix effects (ion suppression effect: 0 to 49.4% and ion enhancement effect: 100% and 264.6%), carryover, reliability and sample extract stability. As a proof-of-principle, urine samples from two patients received a single injection of leuprorelin acetate microspheres (3.75 mg) 30 days before were analyzed and the results proved the applicability of the method.