| Abstract: | The chemical stability of the soman antidotes HGG-12 and HI-6 was studied over the pH range 2–9 at various temperatures. Maximum stability for both oximes was found at pH 2. From Arrhenius plots the predicted shelf life (10% decomposition) was 2.6 years at 25° C and 60 years at 4 °C for both oximes. The apparent energy of activation was 113kJ/mol. The decay rate of both oximes apparently was not influenced by oxime concentration, buffer composition, light, and oxygen. By ion-pair HPLC the following degradation products were indentified: pyridine-2-carbaldoxime, pyridine-2-carbonitrile, 2-pyridone, formaldehyde and 3-benzoylpyridine (for HGG-12) or isonicotinamide and isonicotinic acid (for HI-6). Two additional pyridinium compounds have not yet been identified. The pattern of degradation products varied considerably with pH. |
