(4-Hydroxy-2-oxo-2H-chromen-3-yl)methyl pyrrolidine-1-carbodithioate as a novel, highly selective and sensitive ligand for determination of copper in water and food samples by dispersive liquid–liquid microextraction coupled with microvolume UV–Vis spectrophotometry

Abstract

In this research, a fast, simple, selective, and sensitive spectrophotometric method based on dispersive liquid–liquid microextraction (DLLME) was developed for the ultratrace determination of copper(II) using newly synthesized chromogenic reagent (4-hydroxy-2-oxo-2H-chromen-3-yl)methyl pyrrolidine-1-carbodithioate (HCDTC). The affecting factors in complexation and microextraction steps were investigated and optimized. HCDTC forms highly sensitive yellow-colored complex with copper(II) (1:4 [copper(II): ligand]) in the wide pH range which shows maximum absorbance at 445 nm. In direct determination, Beer’s law was obeyed in the concentration range from 0.1 to 5.0 mg L−1. Molar absorptivity and Sandell’s sensitivity values for Cu(II)–HCDTC complex were 1.3 × 104 and 0.0047 µg cm−2, respectively. However, by applying DLLME, a detection limit as low as 0.3 µg L−1 with preconcentration factor of 92 and relative standard deviation (n = 6) less than 3.5% were achieved. Moreover, calibration graph was linear in the range of 1.0–200 µg L−1. Finally, the proposed method was successfully applied for preconcentration and determination of the Cu(II) in some water and fruit juice samples, and satisfactory results were obtained. Accuracy and reliability of the method were also verified by GF-AAS.