Application of Tungsten-Rhodium Permanent Chemical Modifier in Slurry Analysis: Determination of Cadmium |
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Authors: | Éder C Lima Francisco J Krug Fernando Barbosa Jr Carlos E C Magalhães |
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Institution: | Centro de Energia Nuclear na Agricultura, Universidade de S?o Paulo Postal Box 96, 13400-970, Piracicaba – SP, Brasil,
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Abstract: | A tungsten-rhodium coating on the integrated platform of a transversely heated graphite atomiser (THGA) was used as a permanent
chemical modifier for the determination of Cd in sediment slurries by electrothermal atomic absorption spectrometry. Slurries
were ultrasonicated during 20 s before being delivered to the previously W-Rh treated platform. The permanent W-Rh modifier
remains stable by approximately 250 measurements when 20 μl of slurries containing up to 1.0% m/v are delivered into the atomiser.
In addition, the permanent modifier increases the tube lifetime up to 720 analytical firings. Also, when the W-Rh permanent
modifier was employed, there was less variation of the slope of the analytical curves during the total atomiser lifetime,
resulting in a decreased need of re-calibration during routine analysis, increasing the sample throughput.
The atomiser lifetime was limited to the THGA wall durability, because the W-Rh treated platform was intact after more than
720 analytical firings.
Detection limits based on integrated absorbance for 1.0% m/v slurries were 1.5 ng g−1 Cd for 250 μg W +200 μg Rh permanent modifier and 11.5 ng−1 Cd for 5 μg Pd +3 μg Mg(NO3)2.
Results for the determination of cadmium in sediment slurries using the W-Rh permanent modifier were in agreement with those
obtained with dissolved sample solutions by using Pd + Mg(NO3)2, since no statistical differences were found by the paired t-test at the 99% level.
Received September 6, 1999. Revision December 1, 1999. |
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Keywords: | : Cadmium sediment slurries tungsten and rhodium permanent modifier electrothermal atomic absorption spectrometry |
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