A Fast and Easy QuEChERS-DLLME Method Combined with GC-MS for Ethion and Bifenthrin Residues Determination and Study of Their Dissipation Dynamics in Palm Dates

New fast and efficient analytical method based on QuEChERS followed by dispersive liquid-liquid microextraction (DLLME) was developed for extraction and pre-concentration of residues of ethion and bifenthrin insecticide/acaricides in palm date matrix. GC-MS was used for quantification of the pesticides. The developed method was validated according to the European regulations' requirements. Method accuracy was 102.2% and 96.1% with a precision of 8.4% and 4.3% (intra-day) and 7.9 and 5.1% (inter-day) for ethion and bifenthrin, respectively. The validated QuEChERS and QuEChERS-DLLME methods were compared. Applying DLLME for preconcentration of pesticides lowered the limit of quantification nearly 20 times. By adding the DLLME step using chlorobenzene as extractant, the method achieved better sensitivity and enrichment factor. Matrix effects were evaluated. Developed methods were utilized in analysis of real samples originated from field trial and markets. For field trial, pre-harvest interval (PHI) and dissipation kinetics were investigated. QuEChERS-DLLME method detected ethion in all market samples and bifenthrin in two of them.