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, 17β-estradiol, 17α-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® HLB disks in a semi-automated system (SPE-DEX® 4790). The method involved extracting 10L of whole surface water samples followed by derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide) and analysis by gas chromatography-mass spectrometry. Drying the disks overnight at 25°C followed by elution with ethyl acetate resulted in extraction recoveries between 75.9% and 120% and limits of quantification of 0.290ngL for estrone, 1.37ngL for 17β-estradiol, 0.724ngL for 17α-ethynyl estradiol and 0.119ngL for diclofenac. Despite extracting 10L of sample, obtained limits of quantification for 17β-estradiol and 17α-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 (0.313ngL-5.69ngL). To our knowledge, this is the first study reporting a large volume solid-phase extraction using disks for the determination of estrone, 17β-estradiol, 17α-ethynyl estradiol and diclofenac in whole surface waters.