Determination of phthalate acid esters plasticizers in polyethylene terephthalate bottles and its correlation with some physicochemical properties

A method for the analysis of phthalic acid esters or phthalates (PAEs) in polyethylene terephthalate (PET) bottles based on the use of microwave-assisted extraction (MAE) and liquid chromatography with UV detection (LC-UV) was developed. The microwave-assisted extraction procedure was optimized by a three factors Box-Behnken response surface design. High PAEs recoveries were obtained by microwave-assisted extraction using 70% of acetonitrile at 140 degrees C during 30 min. Moreover, some physical properties of PET samples as thickness, and crystallization and melting temperatures were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. Those parameters were correlated, through Pearson correlation coefficient, with the content of PAEs determined in PET containers (dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP)) and with the content of PAEs in water obtained from a migration test in PET. The migration procedure was based on a standardized procedure (EU 82/711/EEC and 85/572/EEC directives) stipulated by the European Union (EU). The concentrations of PAEs found in PET bottles were between 1.1 and 14.8 mg kg(-1) for DMP, 9.3 and 63.6 mg kg(-1) for DBP and DEP was only detected in one of the 10 analyzed samples at a concentration of 3.1 mg kg(-1). The analysis of the samples obtained by applying the migration test showed that DBP was found in five of the ten analyzed samples reaching concentrations from 14.5 up to 25.6 mu g L-1. DMP was found in five of the ten analyzed samples, with concentrations from 4.1 to 50.6 mu g L-1, whereas DEP was not detected in any of the analyzed samples. The results of the Pearson correlation coefficient indicated that there was a significant correlation between the thickness and the total concentration of PAEs in the PET samples (95% confidence interval), as well as the DBP content in PET samples and the concentration of DBP migrated from bottles to the water (90% confidence interval), indicating that the content of PAEs in the samples and the migration rate of these compounds was related to the physical characteristics of PET bottles.