Investigating the atomization mechanisms in an electrothermal atomizer and vaporizer is important to improve the detection limit, sensitivity, and accuracy in various atomic spectrometries. Electrothermal atomic absorption spectrometry (ETAAS) is a highly sensitive analytical technique that extensively used in the direct determination of numerous elements because of its versality, speed, and specificity. Substantial losses of As due to the vaporization loss of gaseous oxides and As dimers have been reported, particularly when using a pyrolytically coated graphite (PG) furnace.McAllister reported that As4O6(g) is likely to be lost from the graphite furnace during prolonged drying of As samples at relatively low temperatures.
1The As2O3(s) is reduced with carbon:The reaction is endthermic and is carried out at 500 -800˚C. 2 Robinson et al. reported that the formation of gaseous As2 and As4 accounted for some of the analyte loss associated with molecular absorption in radiofrequency carbon atomization cells.3 Koreckova et al. observed absorption bands for As2(g) when samples were introduced on a tungsten wire into a hot graphite furnace, but did not observe the bands when As was introduced on graphite species. 4 Slaverykova and Tsalev carried out a kinetic investigation for analyte losses, such as As, Pb, Sb, and Sn, during a pre-atomization thermal treatment in the range 673 -1073 K. 5 The hold time for the pretreatment was varied between 5 -60 s at different fixed pretreatment temperatures. From the slopes of the linear regression plots, ln A/A0 versus t, the rate constants for the analyte loss process were evaluated. From the slopes of the Arrhenius plots, the apparent activation energies of the analyte loss process were derives. The apparent activation energies (Eas) were evaluated only for the initial stage of the loss process (<40 s). These values were 12±2, 16±2, 58±5, and 175±13 kJ mol -1 , observed for As, Pb, Sb, and Sn, respectively, being ranged in the approximate order of decreasing volatility of the analyte.It is proposed with mass and atomic absorption spectrometry by Styris et al. that As2O3 thermally decomposes, forming As monoxide, higher As oxides, and condensed phase As, which polymerizes and then sublimates as the dimer. 6 Atomization occurs by dissociative adsorption of the oxide and desorption of the resulting As. The following mechanisms were proposed:(1) It was found that Arrhenius plots were composed of two straight portions for As deposited on the PG and NPG furnace walls and of one straight portion for that on active carbon formed from the pyrolysis of ascorbic acid at a low-temperature pyrolysis. To correct the absorbance of the first peak for that of the second peak, the absorbance corresponding to the second peak in the period of the first peak was evaluated by extrapolating the straight line for the second peak to each atomization time. The activation energy (Ea) for the first peak depended on the ratio of the edge carbon species in graphite as the condensed phase based on Raman spec...