1. Chemistry Department, Jomo Kenyatta University of Agriculture and Technology, Nairobi P.O. Box 62000-00200, Kenya
2. Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, FI-40014 Jyvaskyla, Finland
3. Department of Physical Science, University of Kabianga, Kericho P.O. Box 2030-20200, Kenya