Analytical Sciences

Effect of Cobalt as a Chemical Modifier for Determination of Bismuth by Electrothermal Atomic Absorption Spectrometry Using a Tungsten Furnace

Tomohiro NARUKAWA*, Atsushi UZAWA*, Wataru YOSHIMURA* and Tadao OKUTANI**

*Department of Chemistry, Chiba Institute of Technology, Shibazono, Narashino,Chiba 275-0023, Japan
**Department of Industrial Chemistry, College of Science and Technology, Nihon University, Kanda-Surugadai, Tokyo 101-0062, Japan

The effectiveness of cobalt as a chemical modifier was investigated for the determination of bismuth by electrothermal atomic absorption spectrometry using a tungsten furnace. A 10 ml aliquot of the 0.1% m/v cobalt modifier (CoCl2 in 1 M HCl) was dropped onto a tungsten metal board and pre-heating was carried out at 1200ûÃ. Then a sample solution con-taining bismuth was added to the board, charred at a temperature of 1200ûÃ, and the absorbance of bismuth was measured at an atomization temperature of 2400ûÃ. The vaporization loss of bismuth during the charring stage could be suppressed up to 1450ûÃ by the addition of the cobalt modifier. The relative standard deviation at 0.10 mg dm -3 (in 0.05 M HNO3) was less than 4% (n=6), and the detection limit (3 s) was 0.07 ng. The addition of the cobalt modifier can depress the deviation of the measurements, which usually depends on the concentrations of acid and other concomitant substances in the sample solutions. (Keywords: Bismuth, cobalt modifier, tungsten furnace, electrothermal atomic absorption spectrometry)

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