Disk-based solid phase extraction for the determination of diclofenac and steroidal estrogens E1, E2 and EE2 listed in the WFD watch list by GC-MS

The aim of this study was to develop and validate an analytical method for determining estrone, 17 beta-estradiol, 17 alpha-ethynyl estradiol and diclofenac in whole surface water samples at or below the limits of quantification as set out in Decision 2015/495/EU. The method is based on solid-phase extraction using Atlantic (R) HLB disks in a semi-automated system (SPE-DEX (R) 4790). The method involved extracting 10 L of whole surface water samples followed by derivatization with N-methyl-N-(trimethylsilyl)trifiuoroacetamide) and analysis by gas chromatography-mass spectrometry. Drying the disks overnight at 25 degrees C followed by elution with ethyl acetate resulted in extraction recoveries between 75.9% and 120% and limits of quantification of 0.290 ng L-1 for estrone, 1.37 ng L-1 for 17 beta-estradiol, 0.724 ng L-1 for 17 alpha-ethynyl estradiol and 0.119 ng L-1 for diclofenac. Despite extracting 10 L of sample, obtained limits of quantification for 17 beta-estradiol and 17 alpha-ethynyl estradiol were above those set in the Decision 2015/495/EU, while limits of quantification for estrone and diclofenac were lower. The method was applied to six Slovene surface waters, among which four contained detectable concentrations of only diclofenac (0.313 ng L-1-5.69 ng L-1).To our knowledge, this is the first study reporting a large volume solid-phase extraction using disks for the determination of estrone, 17 beta-estradiol, 17 alpha-ethynyl estradiol and diclofenac in whole surface waters. (C) 2017 Elsevier B.V. All rights reserved.