Calibration graphs for lead, cadmium and copper have been obtained in natural water, in centrifuged natural water and. in distilled water. These calibration graphs were repeated in each medium one time when acidified to PH 2.2 and another time when buffered to pH 7.4. The shape of the calibration graphs obtained in the various types of media has been explained with reference to adsorption of metal ions on the suspended particles of the natural water and on the container surfaces. An equation describing the adsorption process has been applied on the calibration graphs obtained for lead, cadmium and copper in natural water samples. The effect of time on the shape of calibration graphs has been also looked into.

Journal of Environmental Science and Health, Part A, Volume 22, Issue 2 February 1987 , pages 125 - 139