Synergistic enhancement effect of room temperature ionic liquids for cloud point extraction combined with UV–vis spectrophotometric determination nickel in environmental samples

A new method based on enhancement effect of room temperature ionic liquids for cloud point extraction trace amounts of nickel combined with UV–vis spectrophotometric determination was developed. Room temperature ionic liquids (RTILs) and diethyldithiocarbamate (DDTC) were used enhancement reagent and chelating reagent, respectively. The addition of room temperature ionic liquids leads to 3.0 times improvement in the determination of nickel. The nonionic surfactant Triton X-100 was used as the extractant. When the temperature of the system was higher than the cloud point of Triton X-100, Ni-DTC complex was extracted into Triton X-100 and separation of the analyte from the matrix was achieved. Some parameters that influenced cloud point extraction and subsequent determination were evaluated in detail, such as the concentrations of RTILs, DDTC and Triton X-100; pH of sample solution, as well as interferences. Under optimized conditions, an enrichment factor of 72 could be obtained, and the detection limit (LOD) for Ni was 0.5 ng mL−1. Relative standard deviations for five replicate determinations of the standard solution containing 50 ng mL−1 Ni was 3.9%. The proposed method was successfully applied to the determination of nickel in certified reference materials with satisfactory results.

Graphical abstractRTILs used as synergic enhancement reagent, the analytical performance of UV–vis spectrophotometric determination was greatly improved.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The first report of CPE coupled with UV–vis spectrophotometry for Ni detection based on the synergetic enhancement effect of RTILs. ► The analytical performance of UV–vis spectrophotometric determination was greatly improved. ► The developed method is a novel and environmental friendship method with impressive detectability.