A simple spectrophotometric determination of fluoride in groundwater has been developed using aluminium - 4, 5-dinitrochrysazin complex. The method is based on the reaction of fluoride with the colored complex to produce colorless aluminium fluoride complex and release the free ligand. The effect of methanol and ethanol solvent on the complex absorption spectra has been examined. The molar absorptivity for the complex in ethanol at 422 and 525 nm was 5630 ± 32 and 680 ± 26 lmol-1 cm-1,respectively. Beer’s law is obeyed in the range of 0.0─5.0 mg l-1 at 370 and 427 nm. Sensitivity, detection limit, quantitation limit, and the percentage recovery of 1.0 mg l-1 fluoride at 427 nm were found to be 0.072 μg ml-1, 0.2mg l-1, 0.5 mg l-1, and 105.2, respectively.Sulphate was the only interfering anion. Still, its effect can be neutralized by adding barium chloride.
4, 5-Dinitrochrysazin complexes; Slovatochromism; Fluoride; Spectrophotometric method; Groundwater
