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 VO 3 − ) 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 55fold 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 (CH 3 ) 2 Te 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.

Highly Efficient Photochemical Vapor Generation for Sensitive Determination of Iridium by Inductively Coupled Plasma Mass Spectrometry

“…Surprisingly, PVG of Ir now remains highly efficient even at very low HCOOH concentrations, wherein the overall efficiency ranges 57–88% for 0.005–0.1 M HCOOH. The Co 2+ and Cd 2+ sensitizers are thus extremely beneficial, and their presence significantly alters the course of PVG possibly via an enhancement the yield of highly reducing CO 2 •– during UV irradiation of HCOOH, ,,,, which likely leads to more efficient reduction of Ir 3+ to Ir 0 and subsequent capture of co-generated CO molecules delivered from photolytic homolysis of HCOOH. However, the irritating question arises as to why so little acid remains sufficient to promote such efficient PVG of Ir.…”

“…A greater effect (additive or synergistic) was reported for several analytes when a combination of two metal sensitizers was employed: namely, Co 2+ and Cu 2+ ions for Mo 6+ ; Cd 2+ and Co 2+ for Os 4+ , Re 7+ , and Ru 3+ ; , and Mn 2+ and Fe 2+ ions for Te 4+ . The mechanism of the action of the metal sensitizers on PVG remains to be fully elucidated, but the latest studies dealing with application of electron paramagnetic resonance spin trapping techniques support the initial thesis that transition metal ions enhance the yield of highly reducing CO 2 •– during UV irradiation of HCOOH. ,,,, …”

“…•− during UV irradiation of HCOOH, 11,27,34,35,37 which likely leads to more efficient reduction of Ir 3+ to Ir 0 and subsequent capture of co-generated CO molecules delivered from photolytic homolysis of HCOOH. However, the irritating question arises as to why so little acid remains sufficient to promote such efficient PVG of Ir.…”

“…PVG is still rapidly developing in scope, having added more than 10 new elements in the past 5 years. − This is also due to the recent introduction of metal sensitizers that significantly increase the PVG efficiency or are even indispensable to initiate PVG of some analytes. Metal sensitizers exhibiting such effects on PVG include: Cd 2+ ions for As 3+ and As 5+ , Se 6+ , and W 6+ ; Co 2+ ions for Bi 3+ , , Cd 2+ , Ge 4+ , Pb 2+ , Sb 3+ , Te 4+ , and Tl + ; Cu 2+ ions for Br – , Cl – , , F – , , Ir 3+ , and Rh 3+ ; Fe 2+ and/or Fe 3+ ions for As 3+ , Bi 3+ , Te 4+ , Mo 6+ , Cd 2+ , and Os 4+ ; Ni 2+ ions for Pb 2+ ; and V 4+ and V 5+ for Te 4+ and Te 6+ . A greater effect (additive or synergistic) was reported for several analytes when a combination of two metal sensitizers was employed: namely, Co 2+ and Cu 2+ ions for Mo 6+ ; Cd 2+ and Co 2+ for Os 4+ , Re 7+ , and Ru 3+ ; , and Mn 2+ and Fe 2+ ions for Te 4+ .…”

Atomic spectrometry update – a review of advances in environmental analysis

“…Results for the two soil CRMs IGGE GSS-3a and GSS-5a were not significantly different from the certified values. Dong et al 178 reported the first use of vanadium species as sensitisers in PVG. The addition of 40 mg L −1 V V (in the form of VO 3 − ) increased the response for both Te IV and Te VI up to 55-fold compared with direct solution nebulisation and 1.5-fold relative to Co 2+ -assisted PVG.…”