Use of dimethylglyoxime for the spectrophotometric flow-based determination of nickel in natural waters

A spectrophotometric flow-based method for the determination of nickel in recreational waters is proposed. In this scenario, the strategy was to devise a miniaturized and automatic system based on sequential injection analysis, aiming for an expeditious, real-time and low-cost determination. For the spectrophotometric determination, dimethylglyoxime was used as color reagent due to its selectivity for nickel. Considering the expected low concentration and low sensitivity of the coloured reaction, a long pathlength flow cell was used to increase the sensitivity. The potential interference of metal ions commonly present in freshwaters was assessed and no significant differences (<10%) were observed, except for manganese. This interference was overcome by adding manganese to the reagent, thus acting as a fixed interference strategy. The limit of detection and quantification were 6.3 and 21.1 µg L ⁻¹, respectively. The method was applied to the quantification of nickel in certified water samples and the results were in agreement with the certified values. Additionally, the method was successfully applied to the quantification of nickel in spiked freshwaters and the results were in agreement with those obtained with the reference method.