Simultaneous derivatization and ultrasound-assisted dispersive liquid–liquid microextraction of chloropropanols in soy milk and other aqueous matrices combined with gas-chromatography–mass spectrometry

Abstract

A novel approach involving ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) and derivatization combined with gas chromatography–mass spectrometry was developed for the determination of chloropropanols in water and beverages. UA-DLLME was optimized as less solvent-consuming and cost-effective extraction method for water, fruit juice, milk and soy milk samples. The effect of parameters such as the type and volume of extraction solvent, the type and volume of dispersive solvent, amount of derivatization agent, temperature, pH of sample and ionic strength was investigated and optimized for each specimen, using experimental designs. By adding acetonitrile as dispersive solvent, N-heptafluorobutyrylimizadole (HFBI) as derivatization agent and chloroform as extraction solvent, the extraction-derivatization and preconcentration were simultaneously performed. The analytical concentration range was investigated in detail for each analyte in the different samples, obtaining linearity with R2 ranging between 0.9990 and 0.9999. The method detection limits were in the range of 0.2–1.8μgL−1 (water), 0.5–15μgL−1 (fruit juices) and 0.9–3.6μgkg−1 (milk) and 0.1–1.0μgkg−1 (soy milk). The method was applied to the analysis of a variety of specimens, with recoveries of 98–101% from water, 97–102% from juices, 99–103% from milk and 97–105% from soy beverage. The relative standard deviation (precision, n=6) varied between 1.3 and 4.9%RSD in water, 2.3 and 5.8%RSD in juices, 1.0 and 5.7%RSD in milk and 3.9 and 9.3%RSD in soy milk. The proposed method was applied to analysis of twenty-eight samples. 1,3-Dichloro-2-propanol was found in an influent water sample from urban wastewater treatment plant (WWTP) (2.1±0.04mgL−1) but no chloropropanols were found in the corresponding effluent water sample. This result suggests that the purification system used in the WWTP has been effective for this compound. Moreover, the results revealed the presence of 3-chloropropane-1,2-diol (3-MCPD) and 2,3-dicloro-2-propanol (2,3-DCP) in soy milk at concentrations within the ranges 19.2–95.0μgkg−1 and 3.0–14.3μgkg−1, respectively. The method is suitable for the determination of target contaminants in liquid samples, particularly for environmental and safety food control fields.