1. Department
of Chemistry, Higher Teachers’ Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon
2. Institute
of Environmental Research (INFU) of the Faculty of Chemistry and Chemical
Biology, Chair of Environmental Chemistry and Analytical Chemistry, Otto-Hahn-Straße 6, D-44221 Dortmund, Germany
3. Inorganic
Chemistry, Department of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Straße 6, D-44221 Dortmund, Germany