Five organophosphorus pesticides (dichlorvos, parathion-methyl, malathion, chlorpyrifos and chlorfenvinphos) were added to crude soybean oil and the oil was refinined by degumming, alkali-refining, bleaching and deodorization. The amount of the organophosphorus pesticides in the oil were determined immediately after each process. The results are as follows :
(1) By degumming treatment, each of organophosphorus pesticides in crude oil decreased slightly.
(2) By alkali treatment, dichlorvos in the degummed oil decreased obviously, though other organophosphorus pesticides remained about 80% or more.
(3) By bleaching treatment with the absorbent, the decreased rate of dichlorvos and chlorfenvinphos was about 70% and 60%, respectively, while the decreased rate of malathion and chlorpyrifos was 30% and 5%, respectively. Parathion-methyl reduced remarkably with absorbent containing activated carbon.
(4) Each of organophosphorus pesticides were completely removed by the deodorization processing at 260°C.
(5) It was confirmed that the organophosphorus pesticides (dichlorvos, parathion-methyl, malathion, chlorpyrifos and chlorfenvinphos) in crude soybean oil were completely removed by usual refining treatment.