Chemical Vapor Generation Atomic Spectrometry Using Amineboranes and Cyanotrihydroborate(III) Reagents

Abstract

Amineboranes of the type L-BH3 (L = NH3; tert-BuNH2; Me2NH; Me3N) and sodium cyanotrihydroborate(III) (NaBH3CN) have been tested as derivatization reagents in the generation of volatile hydrides and elemental mercury following aqueous phase reaction with ionic species of Hg(II), As(III), As(V), Sb(V), Sb(III), Bi(III), Se(IV), Se(VI), Te(IV), and Te(VI). Continuous flow generation atomic absorption spectrometry coupled with a flameless quartz tube atomizer (T = 25 degrees C) and a miniature argon-hydrogen diffusion flame atomizer were employed for the detection of mercury vapors and volatile hydrides, respectively. All of the reductants were able to reduce Hg(II) to the elemental state, giving sensitivities comparable to NaBH4 reduction. Under reaction conditions giving maximum sensitivity for hydride generation with NaBH4, only some amineboranes are able to produce volatile hydrides from all the elements. No evidence of hydride formation was observed from the Se(VI) and Te(VI). In general, the reducing power decreased in the order NaBH4 > H3N-BH3 > tert-BuNH2-BH3 > NaBH3CN > or = Me2HN-BH3 > Me3N-BH3. In comparison with THB, amineboranes and NaBH3CN allowed, in general, a better control of interference effects of Fe(III), Ni(II), Co(II), and Cu(II). Application to determination of mercury in certified reference material is reported. The most likely mechanism of reaction of borane complexes in chemical vapor generation is based on the direct action of hydrogen bound to boron.

Condensation cascades and methylgroup transfer reactions during the formation of arsane, methyl- and dimethylarsane by aqueous borohydride and (methyl) arsenates

“…In particular, it was rather effective for Me 2 AsO(OH) where the formation of Me 3 As was completely eliminated (Table 2).…”

“…It is well-known that thiols reduce arsenic compounds to thiolates such as As(SR) 3 , MeAs(SR) 2 and Me 2 As(SR) [19,20,21,22], which are quantitatively converted by NaBH 4 into the corresponding hydrides [23,24]. Consequently, cold vapor generation by NaBH 4 in the presence of thiols presents an attractive way to estimate the purity of the methylarseno compounds.…”

“…Chemical generation of volatile species (CGVS) of metallic or organometallic compounds by reactions with aqueous NaBR 4 (R = H, alkyl or phenyl group) or XBH 3 (X = NH 3 , NR 3 , CN − ) coupled with atomic or molecular spectroscopy or with mass spectrometry is among the most powerful analytical tools for trace element determination and speciation [1][2][3]. Despite the widespread analytical application of volatile hydride formation for determination of trace amounts of elements such as arsenic, antimony, bismuth, germanium, tin, lead, selenium, tellurium and mercury the mechanism by which they are formed has been debated for many years.…”

“…As the concentration of analytical substrate increases, or the amount ratio of NaBH 4 -to-analyte decreases, various volatile byproducts, such as diarsanes or Me 3 As, are formed [7]. This phenomenon is of great importance to analytical chemists.…”

Chemical Generation of Arsane and Methylarsanes with Amine Boranes. Potentialities for Nonchromatographic Speciation of Arsenic

“…In particular, the efficiency of AB in hydride generation for many analytes was proven to be generally high and very similar to the one of THB, even though with differences in the pattern of dependence from acidity, in HCl. 26 CHG reaction efficiency of As species is severely affected by t h ep r e s e n c eo fL-cysteine, 27,28 Cys, or other thiolic compounds, 20,29 with different yield patterns depending on pH and on the kind of acid medium employed. The effect of Cys on arsanes generation from inorganic arsenic with THB and its modification with acidity has been thoroughly studied with HCl, HClO 4 ,H 2 SO 4 and acetic acid, indicating a strong interaction both with analyte and reductant, and its use as masking agent allowed good control of metal interfering agents.…”