Chemical hydride generation

In addition, traces of heavy metals such as Cu may have a catalytic influence on the formation and dissociation of the hydrides, as investigated by Welz and Melcher (see, e.g., Ref. [185]) in atomic absorption using quartz cuvettes. This effect may also be due to a reaction of the interferent with the NaBH4. The latter can be partly avoided by using fairly high concentrations of acid in the chemical hydride generation, as this was found to be effective for removing interferences of Fe [176]. These interferents can be masked further by complexation with tartaric acid or coprecipitation with La(OH)3. It is advised that calibration should be carried out by standard additions. 

No preconcentration or isolation/separation procedures applied Physico-chemical separation/preconcentration Hydride generation, cold vapor generation (Hg)... 

Efficient Hydrogen Generation from Organic Chemical Hydrides with... 

Removal of thermodynamic restriction through reactive distillation and enhancement of hydrogen generation reactivity due to this concept made it possible to utilize organic chemical hydrides in the field of hydrogen storage from a novel standpoint. 

Catalytic Hydrogen Generation from Organic Chemical Hydrides under Superheated Liquid-Film Conditions by Use of Laboratory-Scale Continuous Reactor... 

To realize efficient hydrogen generation from organic chemical hydrides with the superheated liquid-film-type catalysis in a continuous operation, catalytic dehydrogenation by use of a continuous reactor was investigated on a laboratory scale [13,14]. 

Organic chemical hydrides demand thermal energy at the stage of hydrogen generation in the cyclic reversible system. Notably, the temperature range required for this purpose are so moderate that new roles would be allotted to low-quality thermo-sources such as ICE vehicles. Consumed heat must be larger than an amount of 202.2 kJ/mol-MCH calculated... 

Fig. 12.10 Apparatus for the determination of bismuth by hydride generation Source Reproduced with permission from the American Chemical Society [143]... 

Hydride generation Light absorbed by atoms derived from hydrides that are generated by chemical reaction are measured An excellent technique for a limited number of analytes that are difficult to measure otherwise... 

The hydride generation technique is a technique in which volatile metal hydrides are formed by chemical reaction of the analyte solutions with sodium borohydride. The hydrides are guided to the path of the light, heated to relatively low temperatures, and atomized. It is useful because it provides an improved method for arsenic, bismuth, germanium, lead, antimony, selenium, tin, and tellurium. 

Andrukaitis, E., and Ali R. Sallehy, Chemical Hydride Hydrogen Generator For Military Applications, Proceedings of the NHA Annual Hydrogen Conference 2004, Los Angeles, California, 26-30 April 2004. 

Chemical separation techniques can be used to reduce spectral interferences and concentrate the analyte. These techniques include solvent extraction(39) and hydride generation(39, 46, 47). At Imperial College, the hydride generation technique is being used on a daily basis(46) for the analysis of soils, sediments, waters, herbage, and animal tissue. The solvent extraction technique is ideally suited for automated systems where the increased manipulation is carried out automatically, and a labor intensive step and sources of contamination are avoided. 

For the determination of organotin compounds (tributyltin, triphenyltin, triethyltin, and tetra-ethyltin) a MAE is proposed before the normal phase (NP) HPLC/UV analysis [35], In organotin and arsenic speciation studies, hydride generation is the most popular derivatization method, combined with atomic absorption and fluorescence spectroscopy or ICP techniques [25,36], Both atmospheric pressure chemical ionization (APCI)-MS and electrospray ionization ESI-MS are employed in the determination of butyltin, phenyltin, triphenyltin, and tributyltin in waters and sediments [37], A micro LC/ESI-ion trap MS method has been recently chosen as the official EPA (Environmental Protection Agency) method (8323) [38] it permits the determination of mono-, di-, and tri- butyltin, and mono-, di-, and tri-phenyltin at concentration levels of a subnanogram per liter and has been successfully applied in the analysis of freshwaters and fish [39], Tributyltin in waters has been also quantified through an automated sensitive SPME LC/ESI-MS method [40],... 

To implement an easy and automated means for chemical vapour generation procedures (hydride generation for arsenic, selenium, etc., and cold vapour mercury), which allows for a reduction on the interferences caused by first-row transition metals (such as copper and nickel). FI methods may be readily coupled with almost all the atomic-based spectroscopic techniques (including graphite furnace atomisers). 

A flow injection-hydride generation procedure was defined using experimental designs. Several chemical and ICP operational variables were simultaneously considered, the relevant ones optimised with a central composite design... 

Hydride generation AAS is a well-established technique for the determination of selenium because of its selectivity and sensitivity. The detection limits are improved by concentrating the hydride prior to the transfer to the spectrometer. Cryogenic condensation in a U-tube at liquid nitrogen temperature is a preferred method of pre-concentration. However, selenium hydride is formed essentially only from Se. The selectivity for Se has been combined with various chemical preparation steps to determine the sum of SeIV and Se and the total selenium content of samples. Se concentrations are measured by the difference between the (Se + Se ) and Se contents. The difference between total selenium and (Se + Se ) contents represents the concentrations of Se° and Se2- species. These methods have been used for determinations of selenium species in natural waters. Soluble organic matter in some groundwater samples interferes with the hydride generation determination of selenium. Isolation of humic substances by their adsorption on resins has overcome this problem. 

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