Stability of Standard Solution for Pesticides during Storage

The stability of the standard solutions for 20 organophosphorus, 19 organonitrogen and 7 pyrethroid pesticides during storage under different conditions (solvent, concentration of pesticides, with or without light) was investigated by gas chromatograph (GC). All of the investigated 46 pesticides were stable during twenty days under all conditions except storage under sunlight. It was found that 12 pesticides dissolved in acetone in low concentration decreased under sunlight. Photo-changed compounds of aldicarb, disulfoton, and fensulfothion in acetone were investigated by GC. It was clarified that these pesticides were gradually changed into their oxydative products (sulfoxide and sulfone). Consequently, it is recommendable that the standard solution for pesticides should be dissolved in hexane, in high concentration and kept in the dark.