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

Abstract

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 μl 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 1200°C. Then a sample solution containing bismuth was added to the board, charred at a temperature of 1200°C, and the absorbance of bismuth was measured at an atomization temperature of 2400°C. The vaporization loss of bismuth during the charring stage could be suppressed up to 1450°C 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 (3σ) 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.