A direct and rapid method for determination of total iron in environmental samples and hydrometallurgy using UV–Vis spectrophotometry

• A rapid spectrophotometric method was developed for total iron in samples containing complexing matrix. • The color reaction can be achieved at room temperature without notable time. • This method has excellent sensitivity without complex sample pretreatment or expensive devices. To determine the total iron concentration in aqueous solutions containing complexing matrix, a direct and rapid ultraviolet–visible spectroscopy determination method was developed using the Nitroso R salt as a chromogenic reagent. In the presence of NaI and CTMAB, the experiment shows that Nitroso R salt-Fe complex can produce a significantly sensitive and selective absorbance peak at 710 nm with no notable time for sensing. The experimental factors that affect the procedure such as temperature, acidity and dosages of various reagents were analyzed and optimized. Under the optimized experimental conditions, the limit of detection and limit of quantification of the method was 4.5 × 10 −8 and 1.5 × 10 −7 mol/L. The calibration curve was obtained in a wide linear range of 1.5 × 10 −7 -6.4 × 10 −5 mol/L with good linearity (R 2 = 0.9989). The method was free of any interference with common ions and can determine the iron content in the complex matrix of aqueous samples. The methodology was further validated by the certified reference water samples used for environmental monitoring and agreed with the ICP-OES spectrophotometry results. Compared with the conventional method, the relative standard deviations of the spike test in various actual samples were in the range of 0.31%-2.9% ( n = 5). Good recoveries between 96.4% and 107% were obtained. The proposed method provides great promise for application in-field analysis of iron content in various environmental samples and hydrometallurgical solutions owing to its high sensitivity, low cost, good reproducibility, and no need for any complex pretreatment.