Determination of selenium by hydride generation atomic absorption spectrometry: elimination of interferences from very high concentrations of nickel, cobalt, iron and chromium by complexation

Abstract

The use of an alkaline sample solution for the determination of Se by the hydride generation technique offers the possibility of eliminating the interference from very high concentrations of Ni²⁺, Co²⁺, Fe³⁺, and Cr³⁺. In order to achieve this, complexing agents were employed to mask the interfering metal ions. After addition of the masking agent, the pH was adjusted to 12–13 with NaOH, and sodium tetrahydroborate was finally added in order to reduce selenite to selenide ions. The selenium hydride was generated by acidifying the solution with HCl in a flow system. Ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid (DTPA) were found to be effective masking agents for Ni²⁺ and Co²⁺; the interference from up to 8000 mg l^–1 of Ni²⁺ or Co²⁺ was eliminated. Tartrate was found to be a suitable masking agent for Fe³⁺ and Cr³⁺ up to 5000 mg l^–1. Accurate results were obtained for the National Institute of Standards and Technology Standard Reference Materials 671 Nickel Oxide and 364 Low-alloy Steel, using combinations of DTPA and tartrate as masking agents. The detection limits were 0.1 µg g^–1 for the Nickel Oxide and 0.3 µg g^–1 for the Low-alloy Steel.