Design modification of a solution-cathode glow discharge-atomic emission spectrometer for the determination of trace metals in titanium dioxide

Abstract

This paper describes the quantitative measurement of trace elements in TiO₂ powders using a modified solution-cathode glow discharge-atomic emission spectrometry (SCGD-AES) system. The optimal conditions utilized 0.1 M HNO₃ sample solutions and operated at a voltage of 1060 V with a flow rate of 2.0 mL min⁻¹. The TiO₂ matrix concentration tolerance of the SCGD source was determined to be 10 mg mL⁻¹. Sample solutions were prepared by dissolving different TiO₂ powders using a high temperature acid digestion method. The values determined by SCGD-AES are comparable to those obtained using axial inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The proposed method was validated by quantifying Ag, Ca, Cu, Fe, K, Li, Mg, Na, and Pb in a certified reference material (NIST 154c), where the measurement results obtained by SCGD-AES agreed well with the reference values. In this method, Ti emissions were relatively weak, so that highly sensitive measurements of trace elements in TiO₂ matrices can be conducted with little interference. The detection limits of the trace elements such as Ag, Ca, Cu, Fe, K, Li, Mg, Na, and Pb in TiO₂ powders were 0.08, 2, 2, 5, 0.04, 0.02, 0.04, 0.02, and 0.4 μg g⁻¹, respectively. The enhancement of Pb sensitivity was also studied. Specifically, the limit of detection for Pb improved 6.5-fold to 2 ng mL⁻¹ with the addition of 3% (v/v) formic acid.