Profiling of urinary steroids by lithium ion adduction-based UPLC-MS/MS

RATIONALE: Urine contains free and conjugated steroids. Total and free steroids were comprehensively quantified; UPLC-MS/MS based on Li adduction allowed for detecting thirteen 3-OH-containing steroids, two of which were detected in human urine for the first time. METHODS: Free urinary steroids were isolated by solid-phase extraction (SPE) with 80% acetonitrile. The total steroids were prepared by enzymatic treatment of urine with a cocktail of sulfatase and glucronidase, protein precipitation, and separation with the above SPE. The free and total steroids were separately analyzed by UPLC-MS/MS with and without introduction of Li + solution. The steroids were quantified by two standard curves created using product ion transitions derived from MH + and [M+Li] + . RESULTS: Two groups of human urine, male and female urine, were analyzed. The absolute amount of each steroid was determined based on creatinine levels. The differences between the male and female groups are clearly attributable to sex steroids. 7-OH P5 and 7-OH DHEA were, for the first time, quantified in the total steroids of female urine, and the latter was identified in both female and male urine. CONCLUSIONS: By combining UPLC-MS/MS based on lithium ion incorporation with conventional UPLC-MS/MS, a total of 29 steroids were identified in human urine containing two newly found steroids.