A new (limit) test for heavy metals

Summary

A simple test for heavy metals in aqueous solutions has been developed, which yields a measure for the overall amount of heavy metals present as well as the identity of the contaminating ions. To evaluate the method, known concentrations of standard ion solutions were treated with diethyldithiocarbamic acid and the complexes extracted into ethyl acetate. In one part of the extract the complexed ions were replaced by Cu(II). The absorbance of the yellow Cu(II)-complex was measured at 430 nm and a calibration curve was determined for each investigated ion. In this way it was possible to detect down to 0.5–3 μg ion, depending on the atomic mass and the valency of the ion. As this method gives only an unspecific measure for the total amount of the ions present, the other part of the extract was evaporated and the residue examined by TLC, which in most cases allowed to identify the ions either as such or by the use of a reference ion.