Doping control analysis of intact rapid-acting insulin analogues in human urine by liquid chromatography-tandem mass...

Insulin and related synthetic therapeutics have been prohibited by the World Anti-Doping Agency for athletes demonstrably not suffering from diabetes mellitus. The primary specimen for doping controls has been urine, but the renal excretion of intact human insulin as well as synthetic analogues such as the rapid-acting products Humalog LisPro, Novolog Aspart, and Apidra Glulisine has been reported negligible owing to metabolic degradation. Nevertheless, employing solid-phase extraction in combination with immunoaffinity purification followed by a top-down sequencing-based mass spectrometric approach, an assay was established allowing the identification of three intact rapid-acting synthetic insulins in doping control urine samples. A volume of 25 mL of urine was concentrated, insulin analogues were isolated from the concentrate by immunoaffinity chromatography, and the eluate was analyzed using microbore liquid chromatography/tandem mass spectrometry. Characteristic product ion spectra obtained from 5-fold protonated intact analytes as well as isolated insulin B-chains allowed the unambiguous identification of target analytes with detection limits of 0.05 ng/mL (9 fmol/mL). Moreover, assay validation demonstrated recoveries between 72 and 80% for Humalog LisPro, Novolog Aspart, and Apidra Glulisine, and assay precisions ranged from 9 to 16%. A reliable tool is provided that allows the qualitative determination of rapid-acting insulins in urine specimens collected for sports drug testing.