Determination of Cu and Cd content of groundwater colloids by solid sampling graphite furnace atomic absorption spectrometry

Cu and Cd content of standard reference materials (SRMs), minerals (quartz, calcite, kaolinite, and bentonite), and samples of aquifer colloids, obtained under natural gradient flow conditions, were analyzed by solid sampling graphite furnace atomic absorption spectrometry (GFAAS). Pyrolytically coated tubes, designed for the analysis of liquid samples, were successfully used. Recovery of analytes by solid sampling was 106-112% of the certified values of SRMs. Cu concentration in clay minerals, obtained by solid sampling, was about 9-fold (in kaolinite) and 3-fold (in bentonite) higher than that obtained by nitric acid extraction, indicating that Cu is partially incorporated into the crystal lattice of the minerals. Analysis of aquifer colloids shows that within a 6-month period the average content of Cu and Cd decreased by about 87%. Solid sampling GFAAS was demonstrated to be a convenient method for the study of metal content in small (5 mg) samples of groundwater colloids.