Determination of silicon in nickel-based alloys using electrothermal atomic absorption spectrometry with longitudinal Zeeman-effect background correction and zinc oxide pretreatment

Abstract

The determination of Si in the nickel-based alloy matrices by electrothermal atomic absorption spectrometry (ET-AAS) has been studied. A longitudinal Zeeman-effect correction with end-capped transversely heated graphite atomizer (THGA) is used. When measured at 251.6 nm, spectral interference mainly from Fe is found. Pretreatment for the removal of Ni and Fe from the sample solution of the nickel-based alloys is required. The effects of various modifiers including ethylenediaminetetraacetic acid (EDTA), Mg(NO 3) 2, NH 4H 2PO 4, Pd(NO 3) 2, and tartaric acid are evaluated in terms of the optimization of accuracy, sensitivity and the minimization of background absorption. Sample pretreatments including ammonium and zinc oxide precipitation are evaluated in terms of reducing the non-specific absorption. ZnO precipitation gives more accurate and precise results. The proposed method has been validated with certified reference materials of nickel-based alloys. Values for the silicon content ranged between 0.521 and 0.016%. The characteristic mass is 33.1 pg and the detection limit is 24.8 pg when 20 μl was injected for each ET-AAS measurement. The recovery for the proposed method ranges from 95 to 105%.