Development of a 96-Well Plate Dithiothreitol Method for the Colorimetric Determination of Nickel Ions in Water Samples

A new, simple, and accurate assay was developed for the colorimetric determination of nickel ions in 96-well plates. The proposed method utilized the color change immediately visible even to the naked eye during the reaction of Ni(II) ions with dithiothreitol molecules (DTT). The intensity of the color produced by the formation of the complex between nickel and dithiothreitol is linearly proportional to the concentration of the metal ions in an alkaline environment, at room temperature, and the detection was performed using a mobile phone as the detector. The proposed method had a good linear response between 0.05 and 0.75 mmol L^-1 and a detection limit of 0.13 mmol L^-1 and was successfully applied for the determination of Ni(II) in bottled and surface water samples.