Development of a dispersive liquid-liquid microextraction technique for the analysis of aryloxyphenoxy-propionate herbicides in soy-based foods

In this work, an ionic liquid–dispersive liquid-liquid microextraction (IL-DLLME) method combined with liquid chromatography and diode-array detection (DAD) was used for the determination of four aryloxyphenoxy-propionate herbicides (fenoxaprop-p-ethyl, quizalofop-p-tefuryl, propaquizafop and haloxyfop-p-methyl) in two soy-based foods (soy milk and soy sauce) was used. For this purpose, the phosphonium-based room temperature ionic liquid (trihexyl(tetradecyl)phosphonium bistriflamide) was used as the extractant. The effect of the experimental parameters on extraction efficiency such as type of disperser solvent, disperser solvent/ ionic liquid volumes ratio, pH, nature and concentration of salt in the aqueous phase, sample volume, and centrifugation and extraction times were investigated and optimized. Since matrix effects were detected, the standard addition method was used for quantification. Under the optimized conditions, the proposed sample preparation method coupled to high performance liquid chromatography-diode array detection (HPLC-DAD) had a satisfactory performance to determine the four herbicides in soy sauce and soy milk. The enrichment factors ranged from 18 to 43 and recovery factors from 25 to 66%. Although the recoveries were not high because of the presence of organic solvent in the sample preparation step, the inter-day reproducibility was 8.4% or less, depending on the analyte, the limits of detection (S/N=3) were obtained in the range of 0.12–0.34mgL−1, the limits of quantification (S/N=10) between 0.36 and 1.04mgL−1, and linear ranges from LOQs to 9.26mgL−1. Finally, the IL-DLLME methodology is inexpensive, simple, fast, and environmentally friendly for the determination of the studied herbicides in soy sauce and soy milk. This study constitutes the first application of an IL-DLLME methodology to aryloxyphenoxy-propionate herbicides analysis in commercial soy-derived foods.