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appears to be suitable for this purpose, due to its affinity to phosphates, however it was used only in conventional (liquid
sampling) ETAAS [17].
To verify this assumption, molecular absorption at 217.0 nm and atomic absorption at 213.6 nm lines, by which
presence of PO molecule and phosphorus atoms, respectively were indicated, was measured during atomization (using fixed
atomization temperature 2000°C) of 0.25 ng Pb in presence of 5 g P (both in solution) without and with the addition of 10
g La as La(NO3)3 at various pyrolysis temperatures. This temperature was selected to achieve the best separation of the Pb
atomic absorption from the background signal and was used for all investigations. From Fig. 1 it can be seen, that in the
absence of La(NO 3) 3 the formation of PO have been observed for whole investigated temperature range (400-1200 °C) and
only a small amount of phosphorus was left in the graphite furnace. From the figure also follows, that in the presence of
La(NO 3) 3 the formation of PO have been observed already at the lowest investigated temperature (400 °C). Unfortunately, at
the temperature over 600 °C an increase of absorbance at the 213.6 nm line was observed indicating the increasing amounts
of atomic phosphorus. Over 1000 °C this effect is, however, less pronounced.
Fig. 1a.: Effect of pyrolysis temperature on Pb and P
vaporization in absence of modifier (atomization
temperature 2000°C)
Fig. 1c.: Effect of pyrolysis temperature on Pb and P
vaporization in presence of 10g Pd + 10 g La
(atomization temperature 2000°C)
Fig. 1b.: Effect of pyrolysis temperature on Pb and P
vaporization in presence of 10 g La (atomization
temperature 2000°C)
Lanthanum nitrate has only minor effect on thermal stabilization of Pb, hence the using of another modifier with
analyte stabilization effect is necessary. If La(NO3)3 is used together with Pd, pyrolysis temperature up to 900°C can be
Zborník príspevkov
z 18. medzinárodnej vedeckej konferencie
"Analytické metódy a zdravie loveka", ISBN 978-80-969435-7-9
- 72 -
hotel Falkensteiner, Bratislava
11. - 14. 10. 2010