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

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 mu g 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.