Determination of phthalic acid esters in water samples using core-shell poly(dopamine) magnetic nanoparticles and gas chromatography tandem mass spectrometry

In this work, the first application of core-shell poly(dopamine) magnetic nanoparticles as sorbent for the extraction of a group of eleven phthalic acid esters of interest (i.e. diethyl phthalate (DEP), dipropyl phthalate (DPP), dibutyl phthalate (DBP), bis-isopentyl phthalate (DIPP), bis-n-pentyl phthalate (DNPP), benzylbutyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP)) and one adipate (bis (2-ethylhexyl) adipate, DEHA) from different water samples (Milli-Q, mineral, tap, pond and waste water) is proposed. Analysis were carried out by gas chromatography triple quadrupole tandem mass spectrometry. Parameters that affect the extraction performance were optimized following a step by step approach, being the optimum conditions the extraction of water at pH 6, with 60 mg of sorbent and the elution with 6 mL of dichloromethane. The methodology was validated for the five selected water samples using DBP-d4 as internal standard. Determination coefficients of matrix-matched calibration curves were above 0.9904 in all cases while relative recovery values ranged between 71 and 120%, with relative standard deviation values below 19%. The limits of quantification of the method ranged between 9 and 20 ng/L. Matrix effects were found for most analytes and water samples. Real water samples were also analyzed, finding DEP and DBP at concentrations below 4.20 and 1.23 μg/L, respectively, in mineral, tap and waste water. DCHP, DEHP and BBP were also found in some of the samples at concentrations below the LOQs of the method.