Development of an Ion-Pair Dispersive Liquid-Liquid Microextraction Method Based on a Ternary Deep Eutectic Solvent...

An ion-pair deep eutectic solvent (DES)-based dispersive liquid-liquid microextraction method was introduced and applied for the extraction of some acidic herbicides from edible oil samples prior to their determination by high performance liquid chromatography. First, a ternary DES composed of decanoic acid, dichloroacetic acid, and phosphocholine chloride is prepared under mild conditions. Then, the analytes are extracted into an alkaline solution from the oil samples by deprotonation of the herbicides. Afterward, the deprotonated analytes are extracted into the prepared DES with the aid of tri-butyl amine (as an ion-pair agent) in the presence of acetic acid (as a pH adjustment agent and dispersive solvent). The validation parameters indicated that the method has low limits of detection (0.09-0.72 ng mL-1) and quantification (0.30-2.3 ng mL-1), an acceptable percision (relative standard deviation ≤  9.0%) and high extraction recoveries (85-94%), and enrichment factors (566-626). The method was used in the analysis of 35 edible oil samples to assessment the studied analytes and the presence of haloxyfop was confirmed in three corn oils.