The knowledge of the behavior and fate of pesticides after their application to environmental systems is very important from the environmental, human health and economical points of view. One of the major applications is the definition of safety intervals. This is particularly important for pesticides applied to vegetables and fruits near the collecting period. The use of additives that can enhance the degradation of pesticides with known behavior is an alternative and also important way to solve the problem. The citrate ammoniacal iron (III) show good catalytic properties in comparison test, have commercial formulation, is cheap and has alimentary index E381 which allow to use citrate ammoniacal iron (III) as catalyst in agriculture and food technology. For analysis we choose procymidone in view of prevalence of diseases which demand application of procymidone near harvest. Investigation was performed using LC-MS,GSMS, HPLC chromatography technique in liquid (methanol, acetonitril, hexan) and solid state (silica and cellulose). Before investigation with additive it is necessary to study phototransformation without addition of citrate ammoniacal iron (III) for comparison of phototransformation pathway. Procimidone give one major product in all solvents and in silica – 3,5 dichlorphenyl isocyanat and this is main product in phototransformation with and without addition of citrate ammoniacal iron (III) . Main product can be easy transformed in 3,5dichloroaniline under influence of water or UV irradiation. With addition of [2C6H5O7FeIII·C6H6O7(NH4)2·nH2O] we have essential degradation of procimydone on silica support . After carrying out investigation in liquid and solid state we can say that metabolic pathway with additive is equal to pathway in natural conditions (in silica and organic solvents).