Estimation of Tb³⁺ by mellitic acid sensitized luminescence in methanol

Mellitic acid sensitized luminescence of Tb³⁺ in methanol exhibits a strong emission which is about 500 times more intense than that observed in water. Under optimal conditions, the luminescence intensity exhibits an excellent linear relationship in the concentration range of 5x10^-10-5x10^-8 M with a detection limit of 3x10^-11 M. The interferences due to other lanthanides have been examined and found to be tolerated up to about 100-fold excess and hence estimation of Tb³⁺ in the presence of excess of lanthanides is possible. This method has been applied to the estimation of Tb³⁺ in simulated rare earth and tap water samples and the result is comparable to the result obtained from ICP-MS. Mechanism of enhanced luminescence is also proposed. This is the first report where mellitic acid sensitized luminescence is applied for the estimation of Tb³⁺. (author)