In-situ separation of the matrix for the direct determination of traces of chromium, cobalt, and nickel in titanium dioxide powder by electrothermal atomic-absorption spectrometry with slurry sampling

Abstract

A novel method has been developed for the direct determination of traces of chromium, cobalt, and nickel in TiO₂ powder; it entails slurry sampling and electrothermal atomic-absorption spectrometry (ETAAS) with a polytetrafluoroethylene (PTFE) slurry (6% m/v) as fluorinating reagent. The factors which could affect the vaporization of the matrix and analytes were studied in detail; the fluorinating vaporization behavior of the analyte both in the slurry and in solution were also investigated. Owing to the in-situ separation of the matrix, the matrix influences were reduced significantly. The proposed method has been applied to the direct determination of traces of chromium, cobalt, and nickel in high-purity TiO₂ powder without chemical pretreatment. Under the optimum experimental conditions the detection limits of the analytes (Cr, Co, and Ni) were 1.9 ng g^–1, 2.4 ng g^–1 and 5.4 ng g^–1, respectively, the relative standard deviations (RSD) were 3.4% (n=6, c=7.0 ng mL^–1), 2.9% (n=6, c=0.70 ng mL^–1), and 7.6% (n=6, c=4.0 ng mL^–1), again respectively, and the characteristic masses for Cr, Co, and Ni were 8.4 pg/0.0044A, 9.3 pg/0.0044A, and 40.0 pg/0.0044A, respectively.