I have used up to 20 mM MnCl2 in acidic buffers without visible changes in the color of the solution. Unfortunately it changes quite dramatic above pH of 7- Probably due to the formation of Mn(OH)2, which Arthur already mentioned. It might be further oxidized to a Mn3+ species. During a purification the manganese ist quite stable in Bis Tris at pH7.2 up to 10 mM for some days, but than it starts to become slightly orange. If it is due to oxidation the incorporation of small amounts of a reducing substance might further stabilize the manganese, but I didnt check this carefully.
Christian -- Christian Roth Institut für Bioanalytische Chemie Biotechnologisch-Biomedizinisches Zentrum Fakultät für Chemie und Mineralogie Universität Leipzig Deutscher Platz 5 04103 Leipzig Telefon: +49 (0)341 97 31316 Fax: +49 (0)341 97 31319
