Dm. Santos et al., Thermogravimetric investigations on the mechanism of decomposition of Pb compounds on a tungsten surface, THERMOC ACT, 362(1-2), 2000, pp. 161-168
Tungsten coils are used as electrothermal atomizers in atomic absorption sp
ectrometry (ETA-W), but despite successful applications the atomization mec
hanism is still obscure. The use of the thermogravimetry (TG) can bring som
e information on decomposition pathways for atom formation, simulating the
drying and pyrolysis steps employed in typical heating program cycles. Ther
mogravimetric curves of Pb salts with and without chemical modifiers, such
as ascorbic, oxalic, tartaric acids, and glucose, or interferents (e.g. NaN
O3) were obtained using a lab-made tungsten sample holder in an 90% Ar plus
10% H-2 atmosphere usually employed in ETA-W. Intermediaries and residues
of the pyrolysis step were characterized by X-ray diffraction. These data a
llows a better establishment of parameters for ETA-W and can help to find p
roper conditions to decrease interferences. It was showed that the general
decomposition route is the formation of PbO by heating, oxide reduction by
H-2 in the purge gas followed by volatilization of Pb. (C) 2000 Elsevier Sc
ience B.V. All rights reserved.