1. Chemistry Department, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya
2. Natural Science Department, Catholic University of Eastern Africa, P.O. Box 62157-00200, Nairobi, Kenya
3. Chemistry Department, Multimedia University of Kenya, P.O. Box 30305-00100, Nairobi, Kenya
4. Department of Applied Chemistry, University of Johannesburg, P.O. Box 17011, Corner Beit and Nind Street, Doornfontein, Johannesburg 2028, South Africa
5. Department of Chemistry, University of Johannesburg, P.O. Box 17011, Kingsway Campus, Auckland Park 2006, South Africa