Degradation of pyrazophos and methidathion in fortified red and white wine under conditions of light and darkness

The decomposition of the pesticides methidathion and pyrazophos in red and white wine stored under different conditions was studied. Samples of red and white wine were fortified with 3.25 mg/kg of each of the pesticides. One lot was stored under diffuse daylight and the other in a dark closet. Both lots were stored at the same temperature. Their degradation was followed for 80 days. Half-lives of the pesticide methidathion in white and red wine stored in diffuse daylight were 20.1 and 20.0 days, respectively, and 21.1 and 24.2 days for those stored in conditions of darkness. Corresponding half-lives for pyrazophos were 29.7 and 29.1 days for storage in daylight conditions and 31.1 and 34.5 days in darkness conditions. Photodegradation was not found to play any important role in the decomposition of these pesticides under the conditions used.