Determination of Ni(II) Ions in Natural Objects and Industrial Alloys via a Spectrophotometric Method with 4,5-Dihydroxy-3,6-Dinitrosonaphthalene-2,7-disulfoxic Acid

In this study, a spectrophotometric method for complexing Ni(II) ions with 4,5-dihydroxy-3,6-dinitroso-naphthalene-2,7-disulfoxic acid (HR) as an organic analytical reagent was developed, and the optimal conditions were as follows: λmax = 575 nm, pH = 9.15, universal buffer, HR = 0.05% relative to TNi2+ = 50.0 μg/25 ml and HR = 1.2 ml. The area of obedience to the Bouguer–Lambert–Beer law was determined to be 5.0–55.0 μg/25 ml. Absorption spectra were studied: Sandell’s sensitivity (S) was 0.009174 μg/cm2, and the contrast was ∆ = 65 nm (HR = 510 nm). The composition of the complex and the mechanism of its formation were studied via the equilibrium shift method, the Isomolar series method and Asmus' straight-line method. The molar ratio of the complex was Ni2+:HR=1:2. The molar absorptivities coefficient (εreal=23585), the formation equilibrium constant (Kequil.=1.62•10-8) of the complex formed by Ni(II) with HR, the stability of the complex constant using Babko’s dilution method (β = 1.30∙1023, lgβ = 23.11), the confidence interval of the deviation from the mean value (∆X = 0.227) and the lower limit of detection (Qmin.= 0.6004 μg/25 ml) were determined. The results of the graduated graph were mathematically processed via the method of small squares, and a linear mathematical equation was developed: Yi = 0.0014 + 0.0041Xi. The effects of side ions were studied during the determination of nickel ions. The suggested spectrophotometric method was applied in the analysis of model mixtures and industrial alloys based on aluminum, and the obtained results were metrologically evaluated. In this case, the relative standard deviation (Sr) did not exceed 0.0237.

Determination of Ni(II) Ions in Natural Objects and Industrial Alloys via a Spectrophotometric Method with 4,5-Dihydroxy-3,6-Dinitrosonaphthalene-2,7-disulfoxic Acid Keywords:

Chromogenic reagents , Heavy and toxic metals , Equilibrium shift method , Isomolar series method , Asmus’ correct linear method , Calibration graph