Interference by volatile nitrogen oxides and transition-metal catalysis in the preconcentration of arsenic and selenium as hydrides

Abstract

When tested individually In a clean system, NOa~a nd HNOa are shown not to be serious Inhibitors of AsH3 and H2Se evolution. The real inhibitors of AsH3 and H2Se evolution (encountered when solid samples are oxidatively dissolved In nitric acid) are shown to be correspondingly reduced nitrogen oxides (N02~, etc.) produced In sample digestion. Volatile NO, Interferants can then result upon acidic disproportionation. These volatile NO, species are found to transport with the AsH3 and H2Se analyte. The N203 species Is detected In a cryogenic trap. When dissolved In downstream H2S04 drying agents, the NO, can give rise to powerful oxidants such as NO+ which can accumulate In the H2S04 and thereby account for "memory Interferences" encountered with subsequent samples. The use of sulfamic acid Is Investigated In the preliminary removal of reduced nitrogen oxides such as N02~. Transition metal cation interferences are also studied. Several metal masking procedures previously reported to work well for AsH3 are shown here to fall for the evolution of H2Se. BH3CN" Is shown to be an effective new reductant to evolve AsH3 and H2Se from As(III,V) and Se(IV) In acid media.

Critical evaluation of analytical methods for the determination of trace elements in various matrices: Part I - Determination of selenium in biological materials and water

“…44) indicates that oxides of nitrogen arising from the acidification of nitrite could be responsible for much of the "nitrate" problem. Whether or not selenium(VI) is quantitatively reduced by sodium tetrahydroborate would also appear to be dependent on experimental conditions.…”

A novel introduction system for hydride generation-inductively coupled plasma mass spectrometry: determination of selenium in biological materials

“…This result, comparable to that reported by Ding and Sturgeon 22 who utilised a concentric nebuliser, highlights the superiority of this approach over earlier studies wherein the signal for Se is completely suppressed in the presence of 0.5 M HNO 3 ±2 M HCl when using a conventional hydride generation system. 28 Figures of merit for Se, As, Sn and Sb Detection limits and precision for Se, As, Sn and Sb, determined under standard conditions using both nebulisers, are summarised in Table 2. Values comparable to those reported in other studies utilising hydride generation 1,4,29±31 are achieved and in all cases are limited by the purity of the reagents rather than by the sensitivity of the system.…”

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

“…CHG coupled with various detection techniques, mainly atomic and mass spectrometry, provides one of the most powerful tools used in analytical chemistry for determination and speciation analysis of mercury and the elements of Groups 14,15, and 16 at mass concentration much below 1 μg L -1 level [1]. The almost unique employed reagent in CHG remains THB as the sodium salt or, less frequently, potassium salt.…”

“…The almost unique employed reagent in CHG remains THB as the sodium salt or, less frequently, potassium salt. Other borane complexes such as NaBH 3 CN [15], borane ammonia, and different amine boranes have been employed [16]. Their effectiveness in terms of analytical performance has not been fully exploited, but they have found useful applications in diagnostic and mechanistic studies of CHG [16][17][18][19].…”