Simultaneous enzymatic hydrolysis and extraction of endocrine-disrupting chemicals in fish bile using...

This study describes a new method for the simultaneous extraction and enzymatic hydrolysis of alkylphenols, estrogens, bisphenol-A and phthalate metabolite (mono-2-ethylhexyl ester, MEHP) in fish bile using polyethersulfone (PES) polymer as sorptive material. Parameters affecting the hydrolysis (enzyme amount) and extraction (nature of polymeric material, PES desorption solvent nature and time, PES amount and time profile) were optimised. The optimum conditions were fixed as: 5 PES tubes (1.5 cm length × 0.7 mm o.d.) were added to a vessel with 100 μL of sample, 800 μL of ultrapure water, 1.5 mL phosphate buffer (0.1 mol L(-1), pH 6) and 200 μL of β-glucuronidase (1000 U mL(-1)) enzyme and the mixture was stirred at 37 °C and 550 rpm for 3 h. Quantitative results were obtained after desorption of PES material using 500 μL of ethyl acetate. The extracts were reconstituted in 250 μL of methanol and analysed by liquid chromatography-tandem mass spectrometry, obtaining apparent recoveries in the range of 73-134 % using deuterated compounds surrogates corrections. Relative standard deviations below 27 % were obtained for all target analytes and the method detection limits (MDLs) were in low nanograms per mililliter level for all the studied compounds, except in the case of MEHP which was detected at higher concentration levels (ng μL(-1)) in bile samples that do not allow its MDL determination. Bisphenol A (MDL-10.8 ng mL(-1)), diethylstilbestrol (MDL-1.4 ng mL(-1)) and MEHP (975-2604 ng mL(-1)) were detected in grey mullets captured nearby the wastewater treatment plant of Gernika (Biosphere Reserve of Urdaibai).