[4] Periodate methods: Determination of compounds oxidized to carbonyl acids

Publisher Summary Periodate oxidations are used for structural analysis, particularly for the study of carbohydrates. Methods are described for estimation of the oxidation products, those most frequently encountered including formic acid, formaldehyde, and carbon dioxide. When carbon dioxide is formed during periodate oxidation of sugars and sugar acids, this product usually arises as a result of oxidation of α-carbonyl acid intermediates. Under conditions of strong acidity, periodic acid will not oxidize α-carbonyl acids. The steps described in the procedure include (1) periodate oxidation, (2) termination of periodate oxidation, (3) formation of p-nitrophenylhydrazones, (4) extraction of p-nitrophenylhydrazones from aqueous phase, (5) extraction of carbonyl acid p-nitrophenylhydrazones, (6) determination of concentration of extracted carbonyl acid, (7) reduction prior to periodate oxidation; and (8) determination of carbonyl acids prior to periodate oxidation. The use of p-nitrophenylhydrazine in place of 2,4-dinitrophenylhydrazine also makes it possible to compare directly results of carbonyl acid determinations with and without prior periodate oxidation. The orbital mixer used for extractions between aqueous and organic solvent phases has proved to be extremely efficient and eliminates the need for an aeration mixing apparatus.