Heated Graphite Atomizers

Belsel, W. R. "The Direct Determination of Serum Chromium by an Atomic Absorption Spectrophotometer with a Heated Graphite Atomizer". Anal. Blochem. (1974), 283-292. 

Nowka R, Muller H (1997) Direct analysis of solid samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer and D2-background correction system (SS GF-AAS). Fresenius J Anal Chem 359 132-137. 

Using a newly developed, transversely heated graphite atomizer and D2-back-ground correction (for details see Sections 2.2 and 4.3), Cd, Pb and Cr were determined in cement and river sediment samples. Of the various calibration approaches applied the best results, also in comparison with wet chemical procedures, were achieved with calibration curves constructed by means of different BCR CRMs with different analyte concentrations and usually n = to individual intakes (Nowka and Muller 1997). 

Several types of atom cell have been used for AAS. Of these, the most popular is still the flame, although a significant amount of analytical work is performed using various electrically heated graphite atomizers. This second type of atom cell is dealt with at length in Chapter 3, and the material here is confined to flames. 

In the final step of the multistep process, the carbon in the fiber is converted to graphite by heating at 1400-2500°C. Similarly, silicon carbide fiber can be made by heating fibers that contain long-chain molecules with alternating silicon and carbon atoms ... 

Note that these calculations of the heat of formation of methanol are not purely ab initio (quite apart from the empirical correction terms in the multistep high-accuracy methods), since they required experimental values of either the heat of atomization of graphite (atomization and formation methods) or the heat of formation of methane (formation method). The inclusion of experimental values makes the calculation of heat of formation with the aid of ab initio methods a semiempiri-cal procedure (do not confuse the term as used here with semiempirical programs... 

A Perkin Elmer model 503 atomic absorption spectrophotometer, equipped with Perkin Elmer HGA-2100 heated graphite atomizer (Figure 2), a deuterium arc background corrector (12), and a strip chart recorder, was used. The HGA-2100 graphite furnace was purged with argon. Hollow cathode lamps were used except for cadmium for which an electrodeless discharge lamp (Perkin Elmer) was used. 

In the application of atomic emission spectroscopy for quantitative analysis, samples must be prepared in liquid form of a suitable solvent unless it is already presented in that form. The exceptions are solids where samples can be analysed as received using rapid heating electro-thermal excitation sources, such as graphite furnace heating or laser ablation methods. Aqueous samples, e.g. domestic water, boiler water, natural spring, wines, beers and urines, can be analysed for toxic and non-toxic metals as received with... 

Atomic absorption spectrometry (AAS) relies on the atomization of substances in an appropriate medium, like a flame, a plasma, or a graphite tube, and the capability of the free atoms to absorb light of a specific wavelength [89]. One of the usual techniques for the determination of trace elements is the heated graphite atomizer (HGA), which consists of a graphite tube connected as a resistor in a high electrical current circuit (Figure 6.22). 

The dissociation energy of a compound in solid or gas phase plays an important role for the atomization process, and thermodynamic and kinetic relationships have to be taken into account. However, the conditions in a graphite tube heated up to more than 2000 K are so extreme that only few reference data exist. 

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