Monitoring the sonochemical degradation of phthalate esters in water using solid-phase microextraction

Abstract

The sonochemical degradation of aqueous solutions containing low concentrations of six phthalate esters at an ultrasonic frequency of 80 kHz has been investigated. Ultrasonic treatment was found capable of removing the four higher molecular mass phthalates (di- n-butyl phthalate, butylbenzyl phthalate, di-(2-ethylhexyl) phthalate and di- n-octyl phthalate) within 30–60 min of irradiation. The rest (dimethyl phthalate and diethyl phthalate) were more recalcitrant and nearly complete removal could be achieved only after prolonged irradiation times. The relative reactivity of phthalates was explained in terms of their hydrophobicity. Experiments were carried out at an overall initial phthalate concentration of 240 μg l −1, values of electric power of 75 and 150 W, temperatures of 21 and 50 °C and in the presence of NaCl to study the effect of various operating conditions on degradation. Solid-phase microextraction (SPME) coupled with GC–MS proved to be a powerful analytical tool to monitor the sonochemical degradation of phthalate esters at low μg l −1 concentration levels, minimising the risk of secondary contamination during sample preparation, a major parameter to consider during phthalates analysis. The advantages as well as disadvantages of using SPME are also highlighted.