Electrothermal atomizers tungsten

Zhou, Y., Parsons, P. J., Aldous, K. M., Brockman, P., and Slavin, W. (2001). Atomization of lead from whole blood using novel tungsten filaments in electrothermal atomic absorption spectrometry. Journal of Analytical Atomic Spectrometry 16 82-89. 

Flame methods are the conventional atomization sources used in MS for industrial hygiene (Table I). Air/acetylene at 2150-2400°C is used for the easily atomized elements like lead, cadmium, and zinc. Refractory metals such as tungsten or vanadium require hotter nitrous oxide/acetylene atomization at 2600-2800 C. The need for greater sensitivity and multielement analysis from a single filter has increased the use of electrothermal atomization for tin, vanadium, nickel, and other difficult elements. Formation of hydrides combined with flame atomization has been used in some cases to increase sensitivity. 

Vyskocilova O., Hlavac R. and Puschel P. (1979) Electrothermal atomization from metallic surfaces. Part 1. Design and performance of a tungsten-tube atomizer, Anal Chim Acta 105 263-270. 

Krivan V., Barth P. and Schnurer-Patschan C. (1988) An electrothermal atomic absorption spectrometer using semiconductor diode lasers and a tungsten coil atomizer design and first applications, Anal Chem 70 3625-3632. 

Berndt H. and Schaldach G. (1988) Simple low-cost tungsten-coil atomiser for electrothermal atomic absorption spectrometry, J Anal At Spectrom 3 709-713. 

Hornung D. and Krivan V. (1999) Solid sampling electrothermal atomic absorption spectrometry for analysis of high-purity tungsten trioxide and high-purity tungsten blue oxide, Spectrochim Acta, Part B 54 1177— 1191. 

During the last decade a number of investigations have been directed towards direct analysis of air particulate matter without using sampling on filters. This approach includes either direct injection of air or use of impactor directly in the furnace to be applied as atomizer in electrothermal atomic absorption spectrometry (ETAAS) or electrostatic precipitation of metals in aerosols on a tungsten collecting electrode which afterwards is put in the electrothermal atomizer (Cresser et al., 1988 1992). 

Carbon furnaces and cups have been utilized as electrothermal atomizers but these tend to be rather complex and most work has been with metal strips or filaments of platinum, tantalum, or tungsten. 

S. Xiao-Quan, B. Radziuk, B. Wetz, and O. Vyscocilova. Determination of manganese in river and seawater samples by electrothermal atomic absorption spectrometry with a tungsten atomizer. Journal of Analytical Atomic Spectrometry 8 409-414,1993. 

Electrothermal atom cells have changed radically since their inception in the late 1950s. The majority of electrothermal devices have been based on graphite tubes that are heated electrically (resistively) from either end. Modifications such as the West Rod Atomizer (a carbon filament) were also devised but were later abandoned. Tubes and filaments made from highly refractory metals such as tungsten and tantalum have also been made, but they tend to become brittle and distorted after extended use and have poor resistance to some acids. Their use continues, however, in some laboratories that need to determine carbide-forming elements. For example, silicon reacts with the graphite tube to form silicon carbide, which is both very refractory and very stable. The silicon is therefore not atomized and is lost analytically. Use of a metal vaporizer prevents this. 

Several research groups have designed atomizers with the purpose of separating the analyte from interfering species, to permit simple atomic absorption. While some appear to be effective, none are commercially available. It was shown some years ago that a 150 W tungsten filament from a light bulb could be used as an electrothermal atomizer. More recently, this concept has been used to develop very small portable instruments for onsite measurement of lead in blood. Excellent results have been reported but a commercial model is still awaited. 

Krivan,V, andTheimer, K. H. (1997). Trace characterization ofh h-purity molybdenum and tungsten by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spectrometry involving analyte-matrix separation. Spectrochim.Acta, Part B 52(14), 2061. 

With electrothermal evaporation from a tungsten filament and quartz fiber optics, detection limits are at the 50-100 pg level for many elements, except for Fe which is subjected to spectral interferences from tungsten lines. This was established from the use of different working gases and especially from experiments with the addition of H2 to the argon. In the case of coupling with graphite furnace atomization Cu, Mg and Fe can be determined in serum samples without dilution for Fe and Cu and with a 1 100 fold dilution for Mg [434]. 

Lucic M. and Krivan V. (1999) Analysis of aluminium-based ceramic powders by electrothermal vaporization inductively coupled plasma atomic emission spectrometry using a tungsten coil and slurry sampling, Fresenius J Anal Chem 363 64-72. 

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