Hydride generation-electrothermal

M. Grotti, P. Rivaro and R. Frache, Determination of butyltin compounds by high-performance liquid chromatography-hydride generation-electrothermal atomisation atomic absorption spectrometry, J. Anal. At. Spectrom., 16(3), 2001, 270-274. 

C. Moscoso-Perez, J. Moreda-Pineiro, P. Lopez-Mahia, S. Muniategui, E. Fernandez-Fernandez and D. Prada-Rodriguez, Bismuth determination in environmental samples by hydride generation-electrothermal atomic absorption spectrometry, Talanta, 1(5), 2003, 633-642. 

Olson, L.K., Vela, N.P. and Caruso, J.A. (1995) Hydride generation, electrothermal vaporisation and liquid-chromatography as sample introduction techniques for inductively-coupled plasma-mass spectrometry. Spectrochim. Acta B, 50, 1095-1108. 

Ringmann, S., Boch, K., Marquardt, W., Schuster, M., Schlemmer, G., Kainrath, P. Microwave-assisted digestion of organoarsenic compounds for the determination of total arsenic in aqueous, biological, and sediment samples using flow injection hydride generation electrothermal atomic absorption spectrometry. Anal. Chim. Acta 452, 207-215 (2002)... 

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. 

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)... 

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]. 

There are several sample introduction methods that are used in conjunction with ICP, including nebulization, electrothermal evaporation, gas chromatography, hydride generation, and laser ablation [30]. Laser ablation combined with ICP (LA-ICP) is useful for analysis of solids. In such a source the sample is positioned in a chamber prior to the ICP source, the ablation cell. Argon gas at atmosperic pressure flows through the cell towards the ICP source. The sample is irradiated by a laser beam and... 

Various efficient devices have been utilized for sample introduction into an inductive plasma source, for example the application of several nebulizers, hyphenated techniques, hydride generation, laser ablation and electrothermal vaporization. The role of the solution introduction system in an inductively coupled plasma source is to convert the liquid sample into a suitable form (e.g.,... 

The determination of arsenic by atomic absorption spectrometry with thermal atomisation and with hydride generation using sodium borohydride has been described by Thompson and Thomerson [29], and it was evident that this method couldbe modified for the analysis of soil. Thompson and Thoresby [30] have described a method for the determination of arsenic in soil by hydride generation and atomic absorption spectrophotometry using electrothermal atomisation. Soils are decomposed by leaching with a mixture of nitric and sulfuric acids or fusion with pyrosulfate. The resultant acidic sample solution is made to react with sodium borohydride, and the liberated arsenic hydride is swept into an electrically heated tube mounted on the optical axis of a simple, lab oratory-constructed absorption apparatus. 

Kimbrough and Wakakuwa [276,330] reported on an interlaboratory comparison study involving 160 accredited hazardous materials laboratories. Each laboratory performed a mineral acid digestion on five soils spiked with arsenic, cadmium, molybdenum, selenium and thallium. The instrumental detection methods used were inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry and hydride generation atomic absorption spectrometry. At most concentrations, the results obtained with inductively coupled plasma atomic emission spectrometry... 

Spectrometric techniques based on atomic absorption or the emission of radiation flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and cold vapor (CV)/hydride generation (HG), mainly for trace and ultratrace metal determinations. 

Donard, O.F.X., S. Rapsomanikis, and J.H. Weber. 1986. Speciation of inorganic tin and alkyltin compounds by atomic absorption spectrometry using electrothermal quartz furnace after hydride generation. Anal. Chem. 58 772-777. 

The role of the sample introduction system is to convert a sample into a form that can be effectively vaporized into free atoms and ions in the ICP. A peristaltic pump is typically used to deliver a constant flow or sample solution (independent of variations in solution viscosity) to the nebulizer. Several different kinds of nebulizers are available to generate the sample aerosol, and several different spray chamber designs have been used to modify the aerosol before it enters the ICP Gases can be directly introduced into the plasma, for example, after hydride generation. Solids can be introduced by using electrothermal vaporization or laser ablation. 

We have already seen in Chapter 2 that choice of atomizer system to be used may have a dramatic effect upon sensitivity, and thus upon signal-to-noise ratio. It is necessary to choose not only between flames, electrothermal atomization (ETA), and cold vapour and hydride generation techniques (which are discussed in Chapter 6), but sometimes also between different flames. Those elements which tend to form thermally stable oxides, such as Al, Ti, Si, Zr, may only be determined in a hotter, reducing nitrous oxide-acetylene flame. They cannot be determined with useful sensitivity in the air-acetylene flame. Some elements, Ba and Cr for example, may be determined in air-acetylene, but are more efficiently atomized in nitrous oxide-acetylene. 

The most suitable techniques for the rapid, accurate determination of the elemental content of foods are based on analytical atomic spectrometry, for example, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), and mass spectrometry, the most popular modes of which are Game (F), electrothermal atomization (ET), and hydride generation (HG) AAS, inductively coupled plasma (ICP), microwave-induced plasma (MIP), direct current plasma (DCP) AES, and ICP-MS. Challenges in the determination of elements in food include a wide range of concentrations, ranging from ng/g to percent levels, in an almost endless combination of analytes with matrix speci be matrices. 

H. Matusiewicz, M. Mikolajczank, Determination of As, Sb, Sn, and Hg in beer and wort by direct hydride generation sample introduction - electrothermal AAS, J. Anal. Atom Spectrom., 482 (2001), 652-657. 

W. A. Maher, Determination of selenium in marine organisms using hydride generation and electrothermal atomic absorption spectroscopy, Anal. Lett, A16 (1983), 801-809. 

Hydride generation atomic absorption spectrometry and electrothermal atomisation atomic absorption spectrometry may also be employed for the measurement of selenium in biological samples. A comparison was made (MacPherson et al., 1988) of these methods with the fluorimetric method described here and all three methods were found to give accurate, reproducible results when samples of plasma and urine with certified selenium contents were analysed. 

Chamsaz, M., Arbab-Zavar, M.H., Nazari, S. Determination of arsenic by electrothermal atomic absorption spectrometry using headspace liquid phase microextraction after in situ hydride generation. J. Anal. At. Spectrom. 18, 1279-1282 (2003)... 

Bermejo-Barrera, P., Moreda-Pineiro, J., Moreda-Pineiro, A., Bermejo-Barrera, A. Selective medium reactions for the arsenic(III), arsenic(V), dimethylarsonic acid and mono-methylarsonic acid determination in waters by hydride generation online electrothermal atomic absorption spectrometry with in situ preconcentration on Zr-coated graphite tubes. Anal. Chim. Acta 374, 231-240 (1998)... 

Two Perkin Elmer hydride generation systems are used i.e. the MHS-1 (Mercury/Hy-dride System) electrothermal system and the MHS-10 flame-heated tube system, the latter being applied only for the tin determinations to avoid memory effects. 

---