Hydride generation reagents

Compounds of Types I-III are most easily formed when a hydridocation of the type [PtH(solvent)L2] (L = tertiary phosphine) is allowed to react with a hydride-generating reagent such as [BH4] " or formate. In the former case an intermediate complex containing the coordinated ligand is formed. In the latter case, the formato-complex intermediate decomposes with loss of CO2 and formation of the dihydrido species. When mono-dentate ligands are used, the formation of complexes of Types I or II depends on reaction conditions and on the known equilibration trans-[PtH2L2] =icis-... 

When using the batch generation system, which involves producing the hydride compound from a fixed volume of sample, by the addition of the hydride-generating reagents in a reaction vessel, the analyte vapor is... 

Treatment of trimethyloxosulfonium iodide with sodium hydride generates dimethyloxosulfonium methylide according to the reaction. This reagent has the remarkable... 

Hydride generation techniques for the volatilization and separation of alkyl leads have been infrequently used as the organolead hydrides are not very stable. The commonest derivatization reagents are NaBtC IRR or Grignard reagents. The normal separation systems and methods of detection are used. 

Hydride generation (HG) systems make use of a gas-liquid separator to separate the gaseous hydrides from the liquid reagents prior to introduction... 

Reductant A solution of 1% w/v sodium borohydride (NaBHJ should be freshly prepared in 0.1 M sodium hydroxide (NaOH), and placed in the reductant reagent compartment of the PS Analytical continuous flow hydride generator. 

Previous work (48) with homogeneous analogues showed that Si-H oxidative additions yield cis products. A cis geometry of hydride and silyl may be allowed in catalytic hydrosilation. Because the industral homogeneous hydrosilation catalyst (62) is h PtClg we tested the activity of our surface generated reagent for the reaction of Equation 24. A suspension of the catalyst was irradiated in 1-... 

Some metals, for example, arsenic and selenium, are difficult to analyze by atomic absorption because their analytical wavelengths are subject to considerable interference. These metals, however, are readily converted to gaseous hydrides by treatment with strong reducing reagents such as sodium borohydride. Since the hydrides can be readily separated from the sample matrix, interferences are much reduced. A typical hydride generation AAS is... 

The element may be determined at 196.0 nm by A AS, using a nitrous oxide-acetylene flame (which is more transparent than air-acetylene at this low wavelength), or by AFS in a variety of flames.46,47 The detection limit of both techniques for selenium is around 1 mg 1 1, too low to be useful for environmental analyses. The element is therefore invariably determined by hydride generation techniques, coupled to AAS or AFS detection, as discussed in Chapter 6, section 2, or by furnace AAS, or occasionally by solution spectrofluorimetry using 2,3-diaminonaphthalene as a reagent. If direct flame AAS or AFS are to be used for some reason, then pre-concentration by solvent extraction is necessary.1 However, this approach is rarely used nowadays. 

The reagent most commonly used for hydride generation is sodium tetrahydroborate, in an acid (HCl) medium for inorganic analytes but in the presence of an organic solvent such as hexane [13] or isooctane [14] when organometals are involved. The generic reaction can be written as follows ... 

In a flow injection system the sample flow and a reagent flow are continuously brought together so as to allow a chemical reaction to take place. This reaction produces a gaseous compound, which has to be separated off as in hydride generation, or forms a complex, which can be adsorbed onto a solid phase to be isolated and preconcentrated. In the latter case, elution with a suitable solvent is carried out and the analytes are led on-line into the AAS system. 

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