Effect of cobalt as a chemical modifier for the determination of lead by electrothermal atomic absorption spectrometry using a tungsten furnace

The effectiveness of cobalt as a chemical modifier was investigated for the determination of lead by electrothermal atomic absorption spectrometry using a tungsten furnace. A 10 mu l aliquot of the 0.1% m/v cobalt modifier (CoCl2 in 1 M HCl) was dropped onto a tungsten metal board and preheating was carried out at 1200 degrees C. After the addition of a solution containing lead, followed by charring at a temperature of 1000 degrees C, the absorbance of lead was measured at an atomization temperature of 2400 degrees C. The loss of lead by volatilization could be suppressed at charring temperatures up to 1250 degrees C by the addition of the cobalt modifier. The relative standard deviation at the 0.06 mg l(-1) lead level was less than 3% (n=5) and the detection limit (S/N=3) was 0.07 ng.