Successive Determinations of Platinum(II) and Selenium(IV) with 1,4-Dibromo-2,3-diaminonaphthalene in Aqueous Micellar Solutions

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Highly sensitive successive determinations for Pt^II and Se^IV ions have been developed based upon reactions with 1,4-dibromo-2,3-diaminonaphthalene (Br₂DAN), which forms a near-infrared (NIR) absorbing complex (ε = 1.2 × 10⁵ l mol^-1 cm^-1 at 800 nm) and an emissive complex (ex. 386 nm, em. 604 nm) for Pt^II and Se^IV ions, respectively, in acidic aqueous micellar solutions. In the presence of a cationic surfactant, cetyltrimethylammonium chloride, the detection limits for Pt^II and Se^IV ions are 1.2 ng ml^-1 (3σ) and 0.98 ng ml^-1 (S/N = 3), respectively. Hydrobromic acid plays a key role to enhance the color development of the NIR-absorbing Pt^II complex. The influences of Cu^II and Zn^II ions at the normal human serum levels are readily tolerated, and interference from Fe^III ion at 35 µmol l^-1 is circumvented by the addition of 50 µmol l^-1 of polyaminocarboxylates, such as EDTA.