Determination of iron(III) with salicylic acid by the fluorescence quenching method.

The spectrofluorimetric determination of Fe(3+) using salicylic acid as an emission reagent has been investigated by measuring the decrease of fluorescence intensity of salicylic acid due to the complexation of Fe(3+)-salicylic acid. An emission peak of salicylic acid, which is decreased linearly by addition of Fe(3+), occurs at 409 nm in aqueous solution with excitation at 299 nm. The determination of the ferric ion is in the range 1x10(-6)-10x10(-6) M Fe(3+) (0.0558-0.558 mug/ml) and the detection limit is 5x10(-8) M. The quenching effect of Fe(3+) on the fluorescence intensity of salicylic acid may be considered on the basis of complexation between salicylic acid and Fe(3+). The effects of foreign ions were investigated.