Determination of anabolic steroids in human urine by automated in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

Abstract

A simple, rapid and sensitive method was developed for determining the presence of seven anabolic steroids (boldenone, nandrolone, testosterone, methyltestosterone, epiandrosterone, androsterone, and atnozolol) in human urine. Glucuronide-conjugates of these compounds were hydrolyzed with β-glucuronidase. The anabolic steroids were analyzed by on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). The steroids were separated within 14 min by high performance liquid chromatography using a Chromolith RP-18e column and 5 mM ammonium formate/methanol (35/65, v/v) as a mobile phase at a flow rate of 1.0 mL/min. Electrospray ionization conditions in the positive ion mode were optimized for the MS detection of these compounds. The optimum in-tube SPME conditions were 20 draw/eject cycles with a sample size of 40 μL using a Supel-Q PLOT capillary column for the extraction. The extracted compounds could be desorbed readily from the capillary column by flow of the mobile phase, and no carryover was observed. Using the in-tube SPME LC–MS with SIM mode detection, good linearity of the calibration curve ( r > 0.995) was obtained in the concentration range of 0.5–20 ng/mL, except for stanozolol. The detection limits (S/N = 3) of anabolic steroids were in the range 9–182 pg/mL and the proposed method showed 20–33-fold higher sensitivity than the direct injection method. The within-day and between-day precisions were below 4.0% and 7.3% ( n = 5), respectively. This method was applied successfully to the analysis of urine samples without the interference peaks. The recovery rates of anabolic steroids spiked into urine samples were above 85%. This method is useful to analyze the urinary levels of these compounds in anti-doping tests.