Simultaneous determination of six phthalate esters in bottled milks using ultrasound-assisted dispersive liquid–liquid microextraction coupled with gas chromatography

A new method was developed for the simultaneous determination of six phthalate esters in bottled milks using ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) followed by gas chromatography–flame ionization detection (GC–FID). 0.8 mL of methanol (dispersant) and 40 μL of CCl4 (extractant) were injected into 8.0 mL of milk solution and then emulsified the mixture by ultrasound for 2.0 min to form the cloudy solution. Under the optimum condition, the enrichment factors of the analytes ranged from 220 to 270 fold and the recovery ranged from 93.2% to 105.7%. Good linearity was observed for all analytes in a range of 0.8–51 ng g−1 with the correlation coefficient (r2) ≥0.9992. The limits of detection (LODs) based on signal to noise of 3 were 0.64–0.79 ng g−1. The repeatability evaluated as intra-day and inter-day precision (relative standard deviation, RSD) were less than 4.0% (n = 5). The presented UA-DLLME–GC–FID method was successfully applied to determine the six phthalate esters in different bottled milk products.