Spectrophotometric methods for the determination of fluoride ion using indole-3-acetic acid interaction with iron(III)

Abstract

This study is related to the determination of fluoride ion by the conversion of pink-colored Fe(III) and indole-3-acetic acid (IAA) into a colorless hexafluoride ferrite complex with the addition of fluoride. The optimum conditions of the complex formation were found to be pH 1.7 and a temperature of 60 $^{\circ}$C C. The maximum absorption wavelength of the complex and the detection limit of the method were 525 nm and 0.26 mg/L, respectively. The interfering effects of the different cations (Ag$^{+}$, Al$^{3+}$, Ba$^{2+}$, Ca$^{2+}$, Cd$^{2+}$, Co$^{2+}$, Cu$^{2+}$, K$^{+}$, Mg$^{2+}$, Na$^{+}$, Ni$^{2+}$, Pb$^{2+})$ and anions (SO$_{4}^{2-}$, SO$_{3}^{2-}$, NO$_{2}^{-}$, I$^{-}$, Br$^{-}$, Cl$^{-}$, SCN$^{-}$, CH$_{3}$COO$^{-}$, H$_{2}$PO$_{4}^{-}$, ClO$_{4}^{-})$ were also investigated. The method was applied to standard and real samples and the resulting data were statistically compared at a confidence level of 95{\%} with those obtained with the use of a fluoride-selective electrode.