**2.2. Chemicals and reagents**

All the solutions were prepared in double-distilled water and the reagents were of analytical grade. Metal standard stock solution of 1000 mg/L was prepared by dissolving 1.00 g of the respective metal in one litre of 0.1 M sodium acetate. It was from this solution that subsequent working solutions were prepared from. Separate solutions of 0.01 M nitric acid and 0.01 M sodium hydroxide were prepared and used to adjust the pH of the working solutions to the desired value. The above chemicals and tetramethylethylenediamine (TMEDA) were supplied by Kobian Kenya Ltd. which is Sigma-Aldrich's outlet in Kenya.
