Abstract

A combination of a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method and cloudpoint extraction (CPE) before spectrophotometric analysis has been developed for the determination of carbaryl residues in vegetable samples that include cucumber, cabbage, Chinese cabbage, kale, and yard long bean. The initial surfactantrich phase became colored upon diazotization with 2,4-dimethoxy aniline under alkaline conditions, and the product was monitored at 510 nm. The optimum conditions for CPE were 1.5% (w/v) Triton X-114 in the presence of 1.5% (w/v) NaCl, and 15-min equilibrated at 45 °C. The diazotization was carried out by adjustment using 0.1 mol L 1 DMA, 0.1 mol L 1 NaNO2, and 1.0 mol L 1 HCl followed by hydrolysis at pH 12 using 1.0 mol L 1 NaOH. Under these conditions, the proposed method gave a limit of detection (LOD) of 0.1 mg kg 1, which is 10-fold lower than analysis without preconcentration, and below the maximum residue limit (MRL) set in vegetable samples. Acceptable recoveries ( > 79%) and precision with the relative standard deviation less than 11% were obtained, in good agreement with the results obtained from high performance liquid chromatography (HPLC), at P=0.05. No contamination by carbaryl in any vegetable samples studied was observed. The proposed method is simple, effective, reliable, and can be used for extraction and preconcentration as well as removal of sample matrix interferences.

Keywords: Carbaryl, 2, 4-Dimethoxy aniline, spectrophotometry, QuEChERS, cloud-point extraction, vegetables