1. Analytical Chemistry Division, MINTEK, 200 Malibongwe Drive, 2155 Randburg, South Africa
2. School of Chemistry, University of the Witwatersrand, Private Bag 3,
P.O. WITS, 2050 Johannesburg, South Africa
3. Hydrometallurgy Division, MINTEK, 200 Malibongwe Drive, 2155 Johannesburg, South Africa