Determination of Phthalate Esters in White Spirits by Dispersive Liquid-Liquid Microextraction Combined with High Performance Liquid Chromatography

A novel method for the determination of diisobutyl phthalate(DIBP), dibutyl phthalate(DBP) and butyl benzyl phthalate(BBP) in white spirits has been developed by using dispersive liquid-liquid microextraction(DLLME) coupled with high performance liquid chromatography with a DAD detector. Key DLLME experimental parameters including the type and volume of extractant and disperser solvent, the amount of added salt, extraction time and temperature were examined and optimized. The optimized extraction conditions were as follows: 2 mL of sample diluted with 7 mL of 0.26 g/mL NaCl solution and then mixed with a pre-mixed solution consisting of 60 μL of carbon tetrachloride(extractant) and the same volume of acetonitrile(disperser solvent) by gently shaking for 5 min at room temperature. After centrifugation, the precipitate phase of carbon tetrachloride was taken and diluted with the same methanol before being injected into the analytical column for analysis. The method revealed an excellent linearity over t he concentration range of 1–500 ng/mL with correlation coefficient(r) 0.99. The detection limits were in the range of 0.3–0.8 ng/mL. The enrichment factors varied from 92 to 102. Intra-day and inter-day repeatability values expressed as relative standard deviation were in the range of 1.3%–2.8%, and 2.0%–4.7%(n = 6), respectively. The developed method was applied to the determination of the phthalate esters in 31 white spirits, and 17 out of the detected samples exceeded the legal limit of DBP. The average recovery rates ranged from 92.5%–111.2%. Compared to previous methods, the new procedure is characteristics of simple sample preparation, less organic solvent consumption and higher sensitivity.