Hydrides generation

Advantages include a very acceptable method for the elements listed when other techniques for these elements fail. Sensitivity for these elements is also very good. 

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This experiment describes a fixed-size simplex optimization of a system involving four factors. The goal of the optimization is to maximize the absorbance of As by hydride generation atomic absorption spectroscopy using the concentration of HCl, the N2 flow rate, the mass of NaBH4, and reaction time as factors. 

Numerous methods have been pubUshed for the determination of trace amounts of tellurium (33—42). Instmmental analytical methods (qv) used to determine trace amounts of tellurium include atomic absorption spectrometry, flame, graphite furnace, and hydride generation inductively coupled argon plasma optical emission spectrometry inductively coupled plasma mass spectrometry neutron activation analysis and spectrophotometry (see Mass spectrometry Spectroscopy, optical). Other instmmental methods include polarography, potentiometry, emission spectroscopy, x-ray diffraction, and x-ray fluorescence. 

FLOW INJECTION ELECTROCHEMICAL HYDRIDE GENERATION ATOMIC ABSORPTION SPECTROMETRY EOR THE DETERMINATION OE ARSENIC... 

A flow-injection system with electrochemical hydride generation and atomic absorption detection for the determination of arsenic is described. This technique has been developed in order to avoid the use sodium tetrahydroborate, which is capable of introducing contamination. The sodium tetrahydroborate (NaBH ) - acid reduction technique has been widely used for hydride generation (HG) in atomic spectrometric analyses. However, this technique has certain disadvantages. The NaBH is capable of introducing contamination, is expensive and the aqueous solution is unstable and has to be prepared freshly each working day. In addition, the process is sensitive to interferences from coexisting ions. 

Arsenic is both toxic and cai cinogenic element. It is necessary to have a fast, reliable and accurate method for determination of ai senic in water. The hydride-generation atomic fluorescence spectrometry (HG AFS) is one of the simple and sensitive techniques for the determination of this element in various types of waters. 

Lab method using continuous flow or flow injection analysis hydride generation and atomic absorption spectrometry... 

BS ISO 11041 Particulate arsenic and arsenic Hydride generation and atomic... 

Treatment of dimethylsulfoxide (DMSO) with sodium hydride generates methylsulfinyl carbanion (dimsyl ion), which acts as an efficient base in the production of ylides. The Wittig reaction appears to proceed more readily in the DMSO solvent, and yields are generally improved over the reaction with -butyl lithium (i). Examples of this modification are given. 

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

This apparatus may also be adapted for what are termed hydride generation methods (which are strictly speaking flame-assisted methods). Elements such as arsenic, antimony, and selenium are difficult to analyse by flame A AS because it is difficult to reduce compounds of these elements (especially those in the higher oxidation states) to the gaseous atomic state. 

Although electrothermal atomisation methods can be applied to the determination of arsenic, antimony, and selenium, the alternative approach of hydride generation is often preferred. Compounds of the above three elements may be converted to their volatile hydrides by the use of sodium borohydride as reducing agent. The hydride can then be dissociated into an atomic vapour by the relatively moderate temperatures of an argon-hydrogen flame. 

It should be noted that the hydride generation method may also be applied to the determination of other elements forming volatile covalent hydrides that are easily thermally dissociated. Thus, the hydride generation method has also been used for the determination of lead, bismuth, tin, and germanium. 

The use of the hydride generation method (Section 21.6) is far more sensitive for the determination of the listed elements. 

The procedure followed describes methods for the determination of total levels, and in certain cases, available amounts of trace elements in soils. The determination of arsenic in soil by hydride generation AAS is included. 

Procedure. Follow the conditions recommended by the instrument manufacturers for the determination of arsenic by hydride generation. Typical instrumental... 

Rainer, D., et al., HI-V Transient Hydride Generation, Solid State Technology, pp. 35 0 (June 1993)... 

Vol. 130. Hydride Generation Atomic Absorption Spectrometry. By Jiri Dedina and Dimiter L. Tsalev... 

A different mechanism for reduction processes by [Fe]-hydrogenase 56 is assumed. The hydride generated by splitting dihydrogen is directly transferred to an electrophilic organic center in methenyltetrahydrocyanopterin. As no electrons need to be transferred this reaction requires only one metal center. Due to its structure the center of [Fe]-hydrogenase 56 does not count to the class of ferrates. 

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

Zhang X, Cornelis R, De Kimpe J, and Mees L (1996) Arsenic speciation in serum of uraemic patients based on liquid chromatography with hydride generation atomic absorption spectrometry and on-line UV photo-oxidation digestion. Anal Chim Acta 319 177-185. 

Method abbreviations D-AT-FAAS (derivative flame AAS with atom trapping), ETAAS (electrothermal AAS), GC (gas chromatography), HGAAS (hydride generation AAS), HR-ICP-MS (high resolution inductively coupled plasma mass spectrometry), ICP-AES (inductively coupled plasma atomic emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), TXRF (total reflection X-ray fluorescence spectrometry), Q-ICP-MS (quadrapole inductively coupled plasma mass spectrometry)... 

Munoz O, Velez D, Montoro R (1999) Optimization of the solubilization, extraction and determination of inorganic arsenic [As(III) i- As(V)] in seafood products by acid digestion, solvent extraction and hydride generation atomic absorption spectrometry. Analyst 124 601-607. 

The most frequently used methods for elemental analysis in plastics (certainly in the past) deal with digestions of some kind. Also, some derivatisation methods (e.g. hydride generation for element analysis, or the equivalent TMAH treatment for molecular analysis) may be used to generate volatile species which are more easily separated from each other by chromatography. Derivatisation reactions are often far from being well controlled. 

In ICP-AES and ICP-MS, sample mineralisation is the Achilles heel. Sample introduction systems for ICP-AES are numerous gas-phase introduction, pneumatic nebulisation (PN), direct-injection nebulisation (DIN), thermal spray, ultrasonic nebulisation (USN), electrothermal vaporisation (ETV) (furnace, cup, filament), hydride generation, electroerosion, laser ablation and direct sample insertion. Atomisation is an essential process in many fields where a dispersion of liquid particles in a gas is required. Pneumatic nebulisation is most commonly used in conjunction with a spray chamber that serves as a droplet separator, allowing droplets with average diameters of typically <10 xm to pass and enter the ICP. Spray chambers, which reduce solvent load and deal with coarse aerosols, should be as small as possible (micro-nebulisation [177]). Direct injection in the plasma torch is feasible [178]. Ultrasonic atomisers are designed to specifically operate from a vibrational energy source [179]. 

Other techniques used for organotin speciation comprise GC-FAAS, GC-GFAAS, GC-ICP-MS, HPLC-FAAS, HPLC-GFAAS, HPLC-DCP (after continuous on-line hydride generation), HPLC-ICP-AES, HPLC-ICP-MS, etc. [555], Whereas ICP-AES does not provide an adequate response for ng levels of tin, ICP-MS can detect sub-ng to pg levels. GC-ICP-ToFMS... 

HG-AAS Hydride generation AAS HT-SEC, HTSEC High-temperature size-exclusion... 

Air (particulate lead) Collection of sample onto cellulose acetate filter dissolution in HN03 with heat addition of HCI / H202 and reaction in hydride generator with sodium borohydride to generate lead hydride AAS 8 ng/L 100-101 Nerin et al. 1989... 

Aroza I, Bonilla M, Madrid Y, et al. 1989. Combination of hydride generation and graphite furnace atomic absorption spectrometry for the determination of lead in biological samples. J Anal Atmos Spectra 4 163-166. 

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