UV photochemical vapor generation and in situ preconcentration for determination of ultra-trace nickel by flow injection graphite furnace atomic absorption spectrometry

Abstract

A new and sensitive method is described for the on-line determination and preconcentration of ultra-trace nickel using the coupling of a flow injection system with graphite furnace atomic absorption spectrometry. The method is based on photochemical generation of Ni(CO)₄ and its trapping on the surface of a graphite furnace, the latter accomplished with approximately 35% efficiency by exposing a solution of Ni(II), containing formic acid, to UV irradiation. Optimum conditions for generation and trapping, as well as interferences from concomitant elemental ions, were investigated. A characteristic mass of 10 pg and LOD of 8 pg mL⁻¹ were obtained based on a 2 ml sample volume. The LOD can be further enhanced by increasing sample volume and reaction temperature, or by addition of copper ions. The precision was better than 3% (RSD) at 1 ng mL⁻¹. Environmental Certified Reference Materials were analyzed to validate the accuracy of the proposed method, including SLRS-4 (river water), MESS-3 (marine sediment), TORT-2 (lobster hepatopancreas) and DOLT-3 (fish liver tissue).