A simple, rapid and low cost method for determination of phthalic acid esters (PAEs) including Dimethyl phthalate (DMP), Diethyl phthalate (DEP), Di-n-butyl phthalate (DBP) and Butylbenzyl phthalate (BBP) in water samples was investigated. The method is based on the extraction of PAEs with coacervate made up of decanoic acid reverse micelles and the subsequent determination by HPLC-UV. Effect of parameters such as concentration of tetrahydrofuran (THF) (2-40% v/v) and decanoic acid (20-400 mg in 40 ml total volume), ionic strength (0.0-0.1 M NaCl), pH (1-4) and stirring time (2-60 min) on recoveries (Rs) and enrichment factors (EFs) were investigated and optimized. The optimum condition for extraction was the stirring of 36 ml of water sample with 4 ml of THF containing 100 mg of decanoic acid for 10 min and its centrifugation (10 min, 3500 rpm). Recoveries and enrichment factors of PAEs mainly depended on the amount of decanoic acid and THF making up the coacervate and were not affected by ionic strength of the sample solution (up to 0.1 M of NaCl), pH (1-4), and stirring time (2-60 min). Recoveries, enrichment factors, LODs and relative standard deviations (RSD%) for PAEs were between 87-94%, 187-202, 0.22- 0.30 µg l-1 and 2-5%, respectively. This method was applied to determine PAEs in tap water, river water, and sea water samples. No PAEs were found in tap water. The amount of DMP and DEP in the Babolrood River was 0.87 and 0.67 µg l-1, while in the Caspian Sea was 0.49 and 0.52 µg l-1, respectively.
