Determination of aqueous aluminum with the fluorescent chelating ligand, 2-hydroxy-1-carbazole carboxylate: Part II. Application of ratio fluorescence spectroscopy

A ratio fluorescence (RF) technique is developed for the measurement of low aqueous concentrations of free aluminium ion ([Al(H 2O) 3+ 6]) with little perturbation to the analyte solution. A small amount of the fluorescent aluminum-binding chelating agent 2-hydroxy-1-carbazole carboxylate (HCC −) is added to an analyte solution and the solution fluorescence is measured at two different wavelength settings. The ratio of these two fluorescence intensities is used in conjunction with the solution pH and ionic strength to determine the aluminum concentration. The lower limit of measuring [Al(H 2O) 3+ 6] by this technique is 0.7 μM at pH 4 and 0.06 μM at pH 5. Effects of potential interferences present in natural water solutions are characterized, and the RF method is compared with a standard chemical extraction method of aluminum speciation in aged aluminum hydroxide solutions.