Spectrophotometric Fluoride Determination Using St. John’s Wort Extract as a Green Chromogenic Complexant for Al(III)

Abstract

In this study, we applied an innovative approach of green analytical chemistry to develop a novel and eco-friendly chromogenic agent for fluoride determination by making use of the nontoxic Al(III)-flavonoid complex in a natural extract from St. John’s wort plant. The initial intensely yellow-colored Al(III)-flavonoid complex formed in the plant extract was converted to a colorless AlF6 3– complex with increasing amounts of fluoride, and color bleaching of the Al-flavonoid chromophore (measured as absorbance decrement) was proportional to fluoride concentration. The developed method gave a linear response within the F– concentration range of 0.11–1.32 mM with the LOD and LOQ values of 0.026 mM (0.5 mg L–1) and 0.079 mM (1.5 mg L–1), respectively. The LOD value for fluoride was below the WHO-permissible limit (1.5 mg L–1) and the US-EPA-enforceable limit (4 mg L–1) in water. The possible interference effects of common anions (Cl–, Br–, I–, NO3 –, HCO3 –, SO4 2–, and PO4 3–) and cations (K+, NH4 +, Ag+, Ca2+, Mg2+, Mn2+, Fe2+, and Fe3+) were investigated; the observed interferences from Fe2+, Fe3+, and PO4 3– were easily eliminated by masking iron with the necessary amount of Na2EDTA without affecting the blank absorbance of the Al(III)-flavonoid complex, precipitating phosphate with Ag(I) salt, and partly neutralizing alkaline water samples to pH 4 with acetic acid. The developed method was applied to real water samples and also validated against a reference spectroscopic method at the 95% confidence level.

Facile fabrication of boron and nitrogen co-doped carbon dots for “ON–OFF–ON” fluorescence sensing of Al3+ and F− ions in water samples

“…It also causes anorexia, gastroenteritis, weakness of muscles, muscle stiffness, dyspnea, sweating, and tachycardia. 4 The conventional methods used for the determination of Al 3+ and F − ions are spectrophotometry, 5,6 spectro-uorimetry, 5,7 and atomic absorption spectrometry. 8,9 Some of these methods suffer from low sensitivity and the need for preconcentration steps.…”

Detection of fluoride ions using carbon quantum dots derived from coal washery rejects via an on–off–on fluorescence mechanism: a smartphone-based image-processing and machine learning approach

“…The results revealed that the sensor's detection limit for F − ions was as low as 0.5 ppm, which is substantially lower than the maximum allowable standard limit for fluoride 51 and comparable to recently reported colorimetric and fluorescence based sensors. 52,53 For varying concentrations (0–20 ppm) of F − ions, the relative change in fluorescence intensity ( F / F 0 , where F and F 0 are the fluorescence intensities of the nanocomposite complex in the presence and absence of F − ions) exhibits a linear relationship (Fig. 7(c)), where Y is the relative fluorescence intensity and X is the F − ion concentration (in ppm).…”

Applications of New Generation Solvents for Extraction of Herbal Products Prior to Atomic and Molecular Analysis

“…Green chemistry as a concept was first introduced in 1991 by PT Anastas when he launched a unique program in order to implement sustainable development in the area of chemical technology (7). Green chemistry has 12 principles which serve as guidelines for designing chemical products and methods (8,9) that reduce or occasionally remove the application and generation of harmful and hazardous chemical materials altogether by using solvents and chemicals that are entirely non-toxic to human health as well the immediate environment in order to design and create effective and non-hazardous methods facilitating the use of renewable solvents known as' new generation solvents' or 'solvents of the future' (10). Gu and Jerome proposed the first requirements for a solvent and a process to be considered green based on their availability, biodegradability, flammability, grade, performance, price, recyclability, renewability, stability, storage, toxicity, and synthesis (11).…”