Determination of phthalate esters in sewage by hemimicelles-based solid-phase extraction and liquid chromatography-mass spectrometry

Hemimicelles-based solid-phase extraction was proposed for the concentration of high volume commodity phthalates from wastewater samples prior to their separation and quantitation by liquid chromatography/atmospheric pressure chemical ionization in positive mode, ion trap mass spectrometry. Di-(2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP) and di-n-butyl phthalate (DBP) were concentrated on hemimicelles of sodium dodecyl sulphate (SDS) produced on alumina on the basis of hydrophobic interactions. The recovery of the target compounds was found quantitative under a wide range of experimental conditions (15-255 mg SDS g−1 alumina, pH 2-6 and sample loading volume up to 1 L). Concentration factors of 2500 were achieved by SPE of 0.5 L of sewage samples. The method detection limits found for BBP, DBP and DEHP were 7, 15 and 16 pg, respectively. The relative standard deviation ranged from 2 to 5%, which indicated good method precision. The approach developed was applied to the determination of phthalates in raw and treated sewage samples.