Spectrophotometric determination of cobalt ions in water using bimetallic chemosensor based on sulfa drug azo dye

Abstract

A spectrophotometric technique has been developed for detection of cobalt(II) ions in aqueous solution samples utilising a new chemosensor. This technique relies on the formation of a stable yellow-orange complex at pH = 13 using 4-(2-Hydroxy-naphthalen-1-ylazo)-N-thiazol-2-yl-benzenesulfonamide (H2L) as ligand through complexation with Co(II) ions. At λ = 390 nm, complex absorption was detected. A correlation coefficient of 0.9934 indicated linearity in the concentration range of (1.7–8.4 × 10–5 mol L−1). The limit of detection (LOD) and limit of quantification (LOQ) were assigned to be 0.147 µg ml−1 (2.5 µmol L−1) and 0.489 µg ml−1 (8.3 µmol L−1),respectively. The stoichiometric composition of the complex, which is 2:1 of M:L, was confirmed by the correlation between the continuous variation results and the molar-ratio methods proposed by Job. Additionally, the structure of the solid complex that is produced when H2L reacts with Co(NO3)2.6H2O has been determined by applying different spectroscopic and analytical techniques, confirming the formation of the complex in the same molar ratio as that determined by Job’s method. The geometrical structure of the complex was confirmed to be tetrahedral by a combination of magnetic moment results and UV-Vis spectra.