Graphite furnace, temperature profile

Figure 21-10 Reduction of interference by using a matrix modifier, (a) Graphite furnace temperature profile for analysis of Mn in seawater, (b) Absorbance profile when 10 xL of 0.5 M reagent-grade NaCl is subjected to the temperature profile in panel a. Absorbance is monitored at the Mn wavelength of 279.5 nm with a bandwidth of 0.5 nm. (c) Reduced absorbance from 10 nl of 0.5 M NaCl plus 10 of 50 wt% NH4NO3 matrix modifier. [From M. N. Quigley and F. Vernon, "Matrix Modification Experiment lor Electrothermal Atomic Absorption Spectrophotometry." J. Chem. Ed. 1996, 73. 980.]...

Graphite furnace temperature profile for analysis of Mn in seawater. ib) Absorbance profile when 10 jjiL of 0.5 M reagent grade NaCl are subjected to the temperature profile. Absorbance is monitored at the Mn wavelength of 279.5 nm with a bandwidth of 0.5 nm. 

Figure 21-8 (a) Transversely heated graphite furnace maintains nearly constant temperature over its whole length, thereby reducing memory effect from previous runs. The i vov platform is uniformly heated by radiation from the outer wall, not by conduction. The platform is attached to the wall by one small connection that is hidden from view. [Courtesy Perkin-Bmer Corp., Norwalk, Cl] (to) Heating profiles comparing analyte evaporation from wall and from platform. [From W. Slavin, Atomic Absorption Spectroscopy, Anal. Chem. 1982,54,685A.]... 

Figure 11.14 A typical time-temperature profile for graphite-furnace atomic absorption spectroscopy 1, drying 2, ashing 3, atomization 4, cleaning 5, cooling. From Dean, J. R., Atomic Absorption and Plasma Spectroscopy, ACOL Series, 2nd Edn, Wiley, Chichester, UK, 1997. Reproduced with permission of the University of Greenwich.

Normal graphite furnaces have a temperature profile and thus differences in the spreading of the analyte over the graphite surface may lead to changes in the volatilization behavior from one sample to another. This effect can be avoided by using a transversally-heated furnace, where the temperature is constant over the whole tube length (Fig. 84). The latter furnace, which has been proposed by Freeh et al. 

Fig. 190. Near-wall gas temperature profile for silica-lined graphite furnace at 1500 0 dial.

Pellets of the polymer sample are introduced into the graphite furnace of an atomic absorption spectrometer and heated to temperatufes between 300 and 900°C. The UV absorption bands occuring are examined in the atomic absorption specbrometer and the thermal ultraviolet profiles characteristic of the pigment obtained. Each pigment has a characteristic thermal UV profile at a particular temperature. 

Figure 6 shows the emission and absorption spectral profiles of the lead 283.3 nm resonance line computed for the conditions of graphite furnace AAS using Equation [8]. The line consists of five hyperfine components that are clearly seen in the emission profile. Because of higher temperature and much higher pressure, the absorption profile is wider and shifted towards the longer wavelengths. 

---