Determination of phthalate acid esters in soybean milk using dispersive liquid-liquid microextraction coupled with...

Dispersive liquid-liquid microextraction (DLLME) was coupled with gas chromatography and mass spectrometric detection for the determination of eight phthalate acid esters (PAEs) in soybean milk. Parameters impacting the extraction efficiencies were optimized including organic solvents to extract PAEs from soybean milk, salt concentrations and organic solvents for DLLME. Under the optimal conditions, limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.57-0.79 and 1.90-2.63 ng g^-1, respectively. Linearities varied in the range of 1-16 000 ng g^-1 with the correlation coefficients of 0.9993-0.9998. The precision of the method was 2.9-3.2 in terms of RSD% based on triplicate measurements. The preconcentration factors were in the range of 200-260. The recoveries of eight PAEs were in the range from 79.0 to 110% at three spiked levels. The trace PAEs in five different brands of soybean milk purchased from the market were determined successfully.