Improvements in cobalt determination by thermospray flame furnace atomic absorption spectrometry using an on-line derivatization strategy

An on-line derivatization strategy was developed for improving cobalt sensitivity using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) as the analytical technique. This strategy involves the generation of a volatile cobalt compound, providing better sample vaporization efficiency. The effect of sodium diethyldithiocarbamate (DDTC) as complexing agent on the integrated absorbance signal was evaluated. Parameters including the pH of complex formation, complex concentration and volume, sample volume, flame gas composition and tube atomization configuration were optimized. A wide linear range (from 23 μg L−1 to 3 mg L−1; r2 = 0.9786) was obtained, with the best one (r2 = 0.9992) attained from 23 to 400 μg L−1 with a sample throughput of 30 h−1. The improvement in the detection power was 17-fold when compared to FAAS, which provides 7 μg L−1 as the limit of detection when considered TS-FF-AAS technique. A relative standard deviation (n = 10) of 4% for a cobalt solution containing 50 μg L−1 was attained, and the accuracy of the procedure was evaluated through certified reference materials (IAEA-SL-1, lake sediment; and ISS-MURST-A1, Antarctic marine sediment). Good agreement between the results at the 95% confidence level was observed.