A new environment-friendly supramolecular solvent-based liquid phase microextraction coupled to high performance liquid chromatography for simultaneous determination of six phenoxy acid herbicides in water and rice samples

A green supramolecular solvent (SUPRAS) has been ex situ synthesized and used as the extraction solvent for liquid phase microextraction (LPME) for six phenoxy acid herbicides including 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2-(2,4-dichlorophenoxy)propanoic acid (Dichloprop), 2-(4-Chloro-2-methylphenoxy) propanoic acid (Mecoprop), 4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB) and 4(4-Chloro-2-methylphenoxy) butanoic acid (MCPB) before their analysis by HPLC. The SUPRAS was generated from the aggregation of sodium dodecyl sulfate (SDS) and tetrabutylammonium bromide (TBABr) at the molar ratio of 1:4, in the presence of AlCl3 at ambient temperature. The synthesized SUPRAS was found to be stable for at least one month and a single prepared batch can be used for extraction of 12 samples. The optimum conditions for the extraction were 20 mu L of SUPRAS, 3.5% (w/v) of AlCl3, vortex for 20 s and centrifugation at 6000 rpm for 1 min. The micro-volume extraction phase was settled at the narrow bottom of the centrifugation tube allowing easy collection without any special equipment required, providing high efficiency and reproducibility for HPLC analysis. Under the optimum conditions, the method provided the enhancement factor of 37-149 with the limits of detection in the range of 1-2 mu g L-1. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) was used for rice sample preparation before extraction and analysis by HPLC. The proposed method was successfully applied for the analysis of the studied herbicides in water and rice samples with the good percentage recovery ranged from 81-110 and 81-108, respectively.