The aim of this study was to conduct a precise analysis through a new spectrophotometric method that uses nitrate anions, NO3-, as species with significant toxic potential covertly existing in the composition of several samples of water intended for domestic consumption. Nitrates, NO3-, from the studied groundwater samples quantitatively reacted with phenol disulfonic acid, which led to the synthesis of an intense bright yellow nitro-phenol disulfonic acid compound in the presence of a solution of NaOH, 2 M, and ammonia, 10-12%, 2:1. Nitro-phenol disulfonic acid showed an absorption maximum at a wavelength of ʎ = 402 nm and was obtained in a quantitative proportion perfectly equivalent to the concentration of pure NO3- nitrate anions obtained from the water samples. Through spectrophotometrically dosing the bright-yellow intense nitro-derivative formed at λ = 402 nm in relation to double-distilled H2O as a control, the concentrations expressed in mg/L of pure nitrate NO3- ions in the unknown water samples were directly determined. Following this method, the NO3- nitrate concentrations from all eight unknown groundwater sources were found to be below the maximum allowed reference limit of 50 mg/L. The method proposed was linear over the entire concentration range of the chosen standard solutions (4,00 µg/mL- 40 µg/mL). The linear regression coefficient was R2 = 0.9995198, R2 ≥ 0.9990, and the correlation coefficient was R = 0,9997599, R > 0.9990. The standard error of the regression line was SE = 0,0059577, SE <<1. The detection limit was LOD = 0,8456 μg/ mL, LOD < 1, and the quantitation limit was LOQ = 2,8093 μg/ mL, LOQ < 3. The method used for the visible spectrophotometric analysis of nitrates was subsequently subjected to complete statistical validation.
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New Quantitative Spectrophotometric Analysis in the Visible (VIS) Range of Nitrates, NO3-, from Fresh Groundwater Sources Intended for Domestic Consumption
Published:
11 October 2024
by MDPI
in The 8th International Electronic Conference on Water Sciences
session Numerical and Experimental Methods, Data Analyses, Digital Twin, IoT Machine Learning and AI in Water Sciences
Abstract:
Keywords: significant toxic potential; nitrate anions; new spectrophotometric method ; studied groundwater samples ; phenol disulfonic acid; linear regression coefficient ; Quantitation limit; Detection limit; statistical validation