title: The relation between phosphine sorption and terminal gas concentrations in successful fumigation of food commodities.
abstract: Owing to increased tolerance and the development of resistance in stored product insects to the fumigant phosphine, in recent years there has been a shift in the target terminal concentration from 100 ppm (100 mL m(-3)) to a higher level of 1000 ppm to achieve 100% insect mortality in 7 day commodity treatments. Therefore, there is a need to investigate whether the revised target concentration could be achieved for food commodities fumigated with phosphine at the standard dose of 2 g m(-3) for 7 days under airtight conditions at > or = 25 degrees C. When different types of food commodity (total 74) were fumigated (300 g per replicate) with phosphine at 2 g m(-3) for 7 days, the terminal gas concentrations in the free space of the commodities varied from 0 to > 2000 ppm. In chambers containing no substrate, a 1417 ppm concentration was recorded. Paddy rice, most of the oilseeds, shelled tree nuts, butter beans, cardamom, green gram splits, coriander powder, rice bran and cocoa powder were more sorptive (> or =60%), such that the target concentration of 1000 ppm was not achieved at the end of 7 days. For these commodities, increased doses of 3-6 g m(-3) were required to attain 1000 ppm. In-shell almonds, green cardamom, in-shell peanuts, leaf tea, tamarind pulp and sunflower seeds were exceptionally sorptive (>90%), so that 0, 41, 112, 168, 203 and 217 ppm respectively were noted at the end of 7 days; the dose must exceed 6 g m(-3) for effective fumigation of these commodities.
authors.affiliation: Food Protectants and Infestation Control Department, Central Food Technological Research Institute, Mysore 570 020, India.
authors.forename: Palvai Vanitha
authors.initials: PV
authors.lastname: Reddy
authors.forename: Yellappa
authors.initials: Y
authors.lastname: Rajashekar
authors.forename: Khamrunissa
authors.initials: K
authors.lastname: Begum
authors.forename: Bhadravathi Chandrappa
authors.initials: BC
authors.lastname: Leelaja
authors.forename: Somiahnadar
authors.initials: S
authors.lastname: Rajendran
mesh_terms: D000327:Adsorption; D005504:Food Analysis; D016266:Food Parasitology; D005651:Fumigation / Q000592:standards*; D007306:Insecticides / Q000032:analysis*; D010571:Pest Control / Q000592:standards; D010573:Pesticide Residues / Q000032:analysis*; D010720:Phosphines / Q000032:analysis*
chemical_list: D007306:Insecticides; D010573:Pesticide Residues; D010720:Phosphines; C044646:phosphine