Thirteenth International Conference on Food Studies

Abstract

Paddy field trials were conducted in reversed decline study approach in the main rice production area of Thailand (Suphanburi and Pathumthani provinces) during August to November, 2018. Two paddy field trials were assigned into two controlled plots and two treated plots. Fosetyl-Al 80WG, as recommended rate incorporated with foliar fertilizer, was applied on the treated plots. The samples were collected on the zero-day, the 7th, 14th, 21st, 30th, 45th and 60th days after the last application. The samples were then analyzed for the residues of fosetyl and phosphonic acid in various parts of the rice which as paddy rice, white rice, husked rice, rice bran and hush and calculate expressed as fosteyl. In-house modified-QuPPe method used for the extraction step and then analysis by HPLC equipped with tandem mass spectrometer (LC-MS/MS). The analysis method had been validated for all rice matrices. The limits of quantitation of this method were 0.01 and 0.1 mg/kg for fosetyl and phosphonic acid respectively. The results showed that there was no residue detected in the controlled plots. The residues in the treated plots continuously increased from the last application and then declined after the 14th day. The high concentration of the residues was mostly found in rice bran than others. Phosphonic fertilizer overuse can increase the amount of phosphonic acid residue in the analyzed samples. Thus, the study of phosphonic acid pathway requires more further studies to confirm the farmers’ fertilizer use pattern and to avoid the blocking of concerned products in international trade.