Rotating-disk sorptive extraction for the determination of sex hormones and triclosan in urine by gas chromatography-mass spectrometry: Clean-up integrated steps and improved derivatization

Abstract

Different clean-up stages were coupled to rotating-disk sorptive extraction (RDSE) of testosterone, progesterone, 17 beta-estradiol and triclosan in urine samples prior to derivatization and detection by gas chromatography-mass spectrometry (GC-MS). By using Oasis (R) HLB as the sorptive phase, extraction equilibrium was reached after 60 min at a disk rotation velocity of 2000 rpm.

The factors involved in sample preparation of the urine were comprehensively studied and implemented to minimize matrix effects that were mainly produced by polar pigments in the urine. A 10-fold dilution of the sample was necessary prior to RDSE, followed by a washing step of the sorptive phase with 10% (v/v) methanolic solution and final selective desorption of the analytes with ethyl acetate. Derivatization of the analytes was also studied in detail and implemented prior to GC-MS. The reaction was optimized in terms of derivatizing agent consumption, time and temperature, achieving significant improvements in these factors.

Under the optimized conditions, the matrix effects decreased almost five-fold for all analytes, and the relative recoveries were between 89 and 111% with detection limits in the range of 0.004-0.54 ng mL(-1), whereas the precision, expressed as relative standard deviation (RSD), was below 14%.

Analytes were determined in real samples in the presence and absence of enzymatic hydrolysis, assessing both their free and total forms. The free triclosan concentration was only 10% of the total concentration found in the same sample after hydrolysis. Estradiol and testosterone were quantified with high sensitivity at concentrations between 0.11 and 10.45 and 0.20-21.23 ng mL(-1), respectively. Progesterone was only quantified in a urine sample from a woman during pregnancy.