Rapid screening of edible oils for phthalates using phase-transfer catalyst-assisted hydrolysis and liquid phase microextraction coupled to high performance liquid chromatography-tandem mass spectrometry.

Edible oil is easily contaminated with phthalic acid esters (PAEs). Conventional procedures to analyze individual PAEs require very rigorous experimental conditions that are extremely labor-intensive due to significant procedural contaminations generated by the ubiquitous presence of PAEs in the laboratory environment. In this study, a rapid screening method for PAEs in edible oil was successfully developed. Using a phase-transfer catalyst (terabutylammonium bromide) during oil/water biphasic base hydrolysis of PAEs, the hydrolysis time was decreased from a previously reported time of 20 h to 10 min (80 °C). The resulting phthalic acid in the acidified hydrolysate was extracted with 600 μL of tributyl phosphate and then analyzed by high performance liquid chromatography-tandem mass spectrometry in 6 min. Parameters affecting the hydrolysis of PAEs and the extraction of phthalic acid were optimized, and the analytical method was validated. No obvious matrix effect existed in the edible oils whether an external or internal standard method was used. The detection limit was 1.0 μmol kg(-1), and the quantification limit was 1.3 μmol kg(-1). The recovery rates varied from 86 to 107% with relative standard deviations equal to or lower than 9.9% in all of the tested conditions. Twenty-six samples were analyzed, and the background corrected total PAE content was found to be in the range of <LOD-52.1 μmol kg(-1). This fast and reliable method was not only a practical way to screen oil samples but can also be used as an indicator of false positive or overestimated results in conventional analysis of PAEs. In addition, it presents a new and promising methodology to deal with oil matrices.