Vanadium Species-Assisted Photochemical Vapor Generation for Direct Detection of Trace Tellurium with Inductively Coupled Plasma Mass Spectrometry.

Abstract

Photochemical vapor generation (PVG) is emerging as an alternative sample introduction method in the field of atomic spectrometry. The addition of transition metals can largely improve the PVG yields of elements with the enhancement of 1.4 to 30 000-fold, based on previous reports. In this work, the use of vanadium species as novel "sensitizers" in PVG was first reported, tellurium (Te) was selected as the target. The efficient photochemical reduction of Te was observed in the presence of 9% (v/v) formic acid (FA), 20%(v/v) acetic acid (AA), and 40 mg L-1 of V(V) (existing as VO3-) with the conversion efficiency of 87 ± 3%. Under the selected conditions, there was no significant difference in analytical sensitivity between Te(IV) and Te(VI), making the direct detection of total Te possible. The limit of detection (LOD, 3σ) was 2.9 ng L-1 for Te with inductively coupled plasma mass spectrometry (ICP MS) measurement. Good precisions of 2.3% and 2.2% (relative standard deviations, RSD) for seven times replicate measurement of 0.5 μg L-1 Te(IV) and Te(VI) standard solutions were obtained. The sensitivity was enhanced about 55-fold compared to that using traditional direct solution nebulization. The method was applied for the determination of trace Te in three water samples and two certified reference materials of sediment with satisfactory results. The possible mechanism was investigated. The generation of volatile vanadium along with (CH3)2Te was found in PVG for the first time. The new findings in this work will be helpful for exploration of efficient "sensitizers" in PVG and further expanding the scope of elements amenable to PVG as well.