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Aqueous phase reaction of trialkyloxonium tetrafluoroborates, [R.sub.3][O.sup.+]B[F.sub.4.sup.-] (R=Me, Et) has been tested in the alkylation of simple inorganic anionic substrates such as halogen ions, cyanide, thiocyanate, sulphide and several oxoanions or their corresponding oxoacids. Gaseous products were separated and identified by gas chromatography mass spectrometry (GC-MS). Alkylated derivatives RI, RBr, RCl were obtained for iodide, bromide, and chloride, respectively, while for fluoride its conversion efficiency to RF is very poor. RCN and [R.sub.2]S were obtained for cyanide and sulphide, while thiocyanate gives RSCN as a main reaction product with a minor amount of alkylisothiocyanate, RNCS (

The complex reactivity of the system As-AH-RSH-THB (As = As(III), As(V); AH = HC1, HCIO4, [CH.sub.3]COOH; RSH = L-cysteine (Cys); THB = Na[BH.sup.4])was investigated using continuous flow (CF) hydride generation (HG) coupled either with atomic absorption (AAS) or atomic fluorescence spectrometry (AFS). As[H.sup.3] generation was examined in the presence of Cys by varying acidity and the type of acid, the mixing sequence, and the reaction time of reagents. The strong depression of arsane generation, which is typically observed in the range of acidity of 0.2-2 M HCI, can be addressed to the low reaction rate of thiolborane, hydroboron complexes, or both toward those As(III) substrates that are formed in the same reaction environment. The simultaneous presence of Cys-borane and As(III)-Cys species is at the origin of the gap of the arsane generation efficiency in the 0.2-2 M HCI acidity range. The selective formation of Cys-borane complexes, which are formed faster than As(III)-thiol complexes, can be achieved by a careful choice of the mixing sequence of the reagents. The simultaneous mixing of sample, Cys, and THB is able to reduce substantially the gap of the arsane generation efficiency in the 0.2-2 M HC1 acidity range. These properties were employed to implement a simple method for selective determination of As(III) in samples containing inorganic arsenic: (i) Total inorganic arsenic is determined by sample treatment with 0.2 M Cys for 30 min, acidity 0.1 M HC1, followed by CF-HGAFS; (ii) As(III) is selectively determined in 0.005 M [CH.sub.3]COOH in the presence of Cys using a chemifold setup allowing the simultaneous mixing of sample, 0.2 M Cys and 0.1 M THB. The selectivity, measured from the ratio between the slopes of calibration graphs As(III)/As(V), is 220. The interference effects of Cu(II), Fe(III), Ni(II), Co(II), Ag(I), Pd(II), and Pt(1V) can be kept under control using the simultaneous mixing of all the reagents. The tolerance toward the interferences was almost the same as that obtained by allowing the formation of As(III)-Cys complexes (offline sample pretreatment with Cys for 30 min). The method was tested with the application to the natural waters and mineral well waters analysis employing CF-HG-AFS.

Unknown and controversial aspects related to the mechanisms of hydrolysis of borane complexes and to the mechanisms of chemical vapor generation for trace element determination in strongly acidic media (0.01-10 M HC1) have been investigated and clarified. The overall hydrolysis rates of borane complexes (B[H.sub.4-], [H.sub.3]N-B[H.sub.3]) in the acidity range of 0.2-10 M HCl were several orders of magnitude lower than those predicted by kinetics laws and obtained in the pH range of 3.8-14. The decomposition of the borane complexes takes place stepwise and proceeds through the formation of hydroboron intermediates, [L.sub.x]B[H.sub.[4-x].sup.n] (x = 1, 2, 3), where L could be one or more species among the donor groups [H.sub.2]O, N[H.sub.3], OH-, and Cl- and n is the charge of the hydroboron species (n = 0, +1, -1, depending on L). Some intermediates present surprisingly long lifetimes at elevated acidities and play a key role in determining both the overall hydrolysis rates of borane complexes and the reactivity of Hg(II), As(III), Sb(III), Bi(III), Se(IV), Te(IV), and Sn(IV) in chemical vapor generation for trace element determination. Atomic absorption experiments demonstrated that almost all trihydroboron species (LB[H.sub.[3].sup.n]]), dihydroboron species ([L.sub.2]B[H.sub.[2].sup.n]]), and monohydroboron species ([L.sup.3]B[H.sup.n]) play an active role in the generation of elemental mercury and stibine. Some of these intermediates are inactive or play a marginal role in the generation of arsine, bismuthine, and hydrogen selenide. Hydrogen telluride is preferentially formed by those hydroboron species, which are stable in strongly acidic conditions, while the same species are unreactive in the generation of stannane. The collected experimental evidence is in agreement with the general reactivity of the elements in chemical vapor generation techniques and, together with other literature data, definitely rule out the hypothesis of 'nascent hydrogen' as a possible mechanism of chemical vapor generation by borane complex derivatization.

Amineboranes of the type L-B[H.sub.3] (L = N[H.sub.3]; tert-BuN[H.sub.2]; [Me.sub.2]NH; [Me.sub.3]N) and sodium cyanotrihydroborate(III) (NaB[H.sub.3]CN) 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 NaB[H.sub.4] reduction. Under reaction conditions giving maximum sensitivity for hydride generation with NaB[H.sub.4], 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 NaB[H.sub.4] > [H.sub.3]N-B[H.sub.3] > tert-BuN[H.sub.2]-B[H.sub.3] > NaB[H.sub.3]CN [greater than or equal to] [Me.sub.2]HN-B[H.sub.3] > [Me.sub.3]N--B[H.sub.3]. In comparison with THB, amineboranes and NaB[H.sub.3]CN 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.