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 determining 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 cobalt(II) ions were determined by 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 in the presence of cobalt(II). The ready-made optical sensor indicated good reproducibility, a relatively long lifetime, and stability with an appropriate linear response from 0.1 to 5.0 mg l-1. The detection limit was calculated as 0.03 mg l-1. Further investigations were evaluated 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 indicate that the utilized method successfully determined cobalt(II) in different water samples containing tap water, seawater, and spring water, without pretreatment.