Minimizing Chloride Interferences Produced by Calcium Chloride in the Determination of Cd by Graphite Furnace Atomic Absorption Spectrometry

Cadmium concentrations in CaCl2 extracting solutions at various concentrations were determined by graphite furnace atomic absorption using two background correctors: the deuterium and the high-speed self-reversal background correction systems. Under- and overestimation of the Cd absorbance signals in CaCl2 solutions were observed for concentrations greater than 0.005 M using the deuterium lamp while no important effect was observed using the other background correction system. The analytical performance of the spectrometer for the determination of Cd was studied in 0.01 M CaCl2 solution and single extractions were performed using reference materials and contaminated soil samples. Cadmium was determined using the two background correction systems and a third method, which consists of the use of the deuterium lamp without any chemical modifier, was added to the study. The results showed that the third method was unable to determine Cd concentrations in the CaCl2 solution due to the presence of extractable arsenic and iron. For solutions without any dilution or diluted with a very low dilution factor, the CaCl2-extractable Cd concentrations measured using the deuterium lamp were systematically below those found using the high-speed self-reversal method. These differences were explained by the presence of chloride ions in the atomization step.