Expanded test method for peptides >2 kDa employing immunoaffinity purification and LC-HRMS/MS

Bioactive peptides with an approximate molecular mass of 2-12 kDa are of considerable relevance in sports drug testing. Such peptides have been used to manipulate several potential performance-enhancing processes in the athlete's body and include for example growth hormone releasing hormones (sermorelin, CJC-1293, CJC-1295, tesamorelin), synthetic/animal insulins (lispro, aspart, glulisine, glargine, detemir, degludec, bovine and porcine insulin), synthetic ACTH (synacthen), synthetic IGF-I (longR(3) -IGF-I) and mechano growth factors (human MGF, modified human MGF, 'full-length' MGF). A combined initial test method using one analytical procedure is a desirable tool in doping controls and related disciplines as requests for higher sample throughput with utmost comprehensiveness preferably at reduced costs are constantly issued. An approach modified from an earlier assay proved fit-for-purpose employing pre-concentration of all target analytes by means of ultrafiltration, immunoaffinity purification with coated paramagnetic beads, nano-ultra high performance liquid chromatography (UHPLC) separation, and subsequent detection by means of high resolution tandem mass spectrometry. The method was shown to be applicable to blood and urine samples, which represent the most common doping control specimens. The method was validated considering the parameters specificity, recovery (11-69%), linearity, imprecision (<25%), limit of detection (5-100 pg in urine, 0.1-2 ng in plasma), and ion suppression. The analysis of administration study samples for insulin degludec, detemir, aspart, and synacthen provided the essential data for the proof-of-principle of the method.