Highly sensitive spectrofluorimetric kinetic determination of ultratrace amounts of vanadium(V) based on the oxidation of 1,8-diaminonaphthalene by bromate

A highly sensitive catalytic quenching spectrofluorimetric method was described for the determination of V(V) based on its catalytic effect on the oxidation of 1,8-diaminonaphthalene by potassium bromate with Tiron as an activator in weakly acidic medium and the reaction mechanism was investigated. The reaction was followed spectrofluorimetrically by measuring the fluorescence intensity of 1,8-diaminonathphlene (DAN) (lambda(ex) = 356 mn, lambda(em) = 439 nm) at a fixed time of 5 min from initiation of the reaction. Under the optimum conditions. vanadium(V) can be determined in the range 0.05-50.0 ng ml(-1) with a S.D. = 0.024 for 15 times measurements. The detection limit of the method was down to 0.0088 ng ml(-1) and the catalytic reaction activation energy was found to be 43.92 kJ mol(-1). The proposed method was tested for the determination of vanadium(V) in rice and natural water samples. (C) 2002 Elsevier Science B.V. All rights reserved.