Fabrication of a New Selective Optical Sensor for Cobalt Determination Using 1-Nitroso-2-naphthol and Monitoring of Cobalt in Water Samples

In this study, the researcher has focused on manufacturing a new, highly selective, and simple optical membrane for the determination of cobalt (II) ions in aqueous solutions. The cobalt (II) is first oxidized when using hydrogen peroxide (H2O2) solution, to eliminate the effect of the concomitant species and increase the selectivity in the determination of cobalt (II) in real samples. The obtained cobalt (III) ions were determined through recording the absorbance intensity of the new selective and sensitive thin optically transparent sensor. 1-nitroso-2-naphthol (1N2N) is used as a sensitive, selective and stable complexing ligand to change the absorbance of the transparent membrane into the presence of cobalt (III). The ready-made optical sensor indicated a good reproducibility and a relatively long lifetime and stability with an appropriate linear response from 0.1 to 5.0 mg L-1. The limit of detection was obtained 0.03 mg L-1. Further investigations were evaluated in an intra-day and inter-day precision (RSD %) 2.76-4.46% and 0.89-5.39%, one after another, and the average percentage of relative error (RE %), was in the range of 1.89 to 3.41. The results indicated that the utilized method could successfully determine cobalt (II) in different water samples containing tap water, seawater and spring water, without any pretreatment.