An emulsification liquid-liquid microextraction (ELLME) method was successfully developed using phenolic based deep eutectic solvent (DES) as an extraction solvent for the determination of phenoxy acid herbicides, dicamba and MCPA in environmental water samples. Five different phenolics based DES were successfully synthesized by using phenol (DES 1), 2-chlorophenol (DES 2), 3-chlorophenol (DES 3), 4-chlorophenol (DES 4) and 3,4-dichlorophenol (DES 6) as the hydrogen-bond donor (HBD) and choline chloride as the hydrogen-bond acceptor (HBA). The DESs were mixed at a 1:2 ratio. A homogenous solution (clear solution) was observed upon the completion of the successful synthesis. The synthesized DESs were characterised by using FTIR and NMR. Under optimum ELLME conditions (50 µL of DES 2 as extraction solvent; 100 µL of THF as emulsifier solvent; pH 2; extraction time; 5 min), enrichment factor (EF) obtained for dicamba and MCPA were 43.1 and 59.7, respectively. Limit of detection (LOD) and limit of quantification (LOQ) obtained for dicamba was 1.66 and 5.03 µg/L respectively, meanwhile for MCPA was 1.69 and 5.12 µg/L, respectively. The developed ELLME-DES method was applied on paddy field water samples, with extraction recoveries in the range of 27-91% for dicamba and 82-96% for MCPA.

A 1.5 mL of ultrapure water containing 0.1 mg L^-1 of dicamba and MCPA of pH 2 was transferred into a centrifuge tube. 100 µL of DES (extraction solvent) and THF (emulsifier solvent) were added to the sample. The tube was placed on the vortex mixer at 2500 rpm for 5 min. The solution was cloudy after vortexing which was caused by the aggregation of DES droplet from the aqueous phase. The targeted analytes were simultaneously extracted to the DES phase during this process. The solution was then centrifuge at 3400 rpm for 10 min to separate the DES phase from the aqueous phase. The extract was dried under a steady stream of nitrogen gas at room temperature and reconstitute with 25 µL of mobile phase before being injected into HPLC system. All data obtained from HPLC analysis were interpolated through a calibration curve to determine the enrichment factor and recovery.