Analysis of Fluoride:
Fluoride is significant component of potable water. The growth of teeth especially in children is impaired in the absence of fluoride thus, an excess of fluoride in water causes fluorosis. It, thus, becomes pertinent to ascertain and control the amount of fluoride in potable water.
Several methods based on substitution reaction are known for the determination of fluoride ions. The most important one is the one which includes the creation of a ternary complex along with zirconium and calcium blue. This method is associatively free from interferences. The reaction occurs at a pH of 2.5 and the excitation is at 350 nm along with an emission of 410 nm. The method is quite rapid and has sensitivity in the ppb range.
The other method of analysis includes quenching fluorescence intensity of Zr-alizarin complex. The quenching of fluorescence is straight proportional to the concentration of fluoride within water. Zr-alizarin complex is acquired at a pH 4.6 and has the excitation and emission wavelengths as 470 and 520 nm, correspondingly. As little as 0.001 µg/ml of fluoride could be analysed through this method, therefore, various metals such as Be, CO, Cr, Cu, Fe, Ni, Th, and PO3- ions show extremely strong interference and they must be erased before fluorescence measurement.