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Off-line preconcentration for determination trace amounts of niobium (V) using benzoquinone derative as a new reagent

A.A.El-Sayed, Mostafa M.Hamed, S.A.El-Reefy

A simple and accurate method for spectrophotometric determination of Nb (V) is described. This method is based on the reaction of Nb (V) with and derivative of 1,4-Benzoquinone (1,4-dichloro-2,5-dihydroxyquinone) as a specific spectrophotometric reagent in 1.8-2.0MHCl. The molar absorptivity and sensitivitywere found to be 5.04 ×104 L.mol-1.cm–1 and 0.00184 ìg.cm2, respectively. The concentration range specified for the determination of Nb (V) was 0.25-2.50 ppm, while applying derivative spectroscophotometeric approach, Nb (V) can be determined as lowas 60.0 ppb.Moreover, off-line preconcentration procedure was exploited in combination with first derivative spectrophotometry to enhance the selectivity and sensitivity. Based on this modification, such method showed a detection limit as low as 10.0 ppb Nb (V). The proposed method were successfully applied to the determination of Nb (V) in different alloy samples and steels.