Sorption and desorption dynamics of ethyl formate and propylene oxide as fumigants in durable agricultural commodities

Abstract

Ethyl formate (EF) and propylene oxide (PPO) are promising alternative fumigants for stored products. Sorption and desorption behaviors of EF and PPO were studied in five commodities. EF and PPO were highly and moderately sorptive, respectively, into the treated commodities. Pinto beans, wheat flour and corn were highly sorptive compared to wheat kernels and tobacco leaves. The headspace concentrations of EF decreased after 24 h of fumigation by the average percentages of 93.5, 65.0, 78.9, 98.6 and 52.6% fumigated at 50 mg/L, while similar percentages of 93.5, 61.1, 78.7, 98.0, and 52.3 fumigated at 100 mg/L were found for wheat flour, wheat kernels, corn, pinto beans and tobacco leaves, respectively. Declines in percentages for headspace concentrations of PPO by wheat flour, wheat kernels, corn, pinto bean and tobacco leaves were 90.7, 43.5, 77.6, 97.6, and 77.0 at 50 mg/L, and were 90.3, 41.9, 77.8, 96.6 and 78.7% at 100 mg/L, respectively, by the end of the 24-h exposure period. Sorption rates of EF (mg/kg commodity) in wheat flour, wheat kernels, corn, pinto bean and tobacco leaves were 280.4, 192.2, 233.0, 295.6, 525.8, at 50 mg/L and were 560.2, 361.3465.1, 588.2, and 1046.4 at 100 mg/L, respectively after 24 h of fumigation. Sorption rates of PPO (mg/kg commodity) were 271.9, 128.6, 229.5, 292.8, 770.7 at 50 mg/L and were 541.6, 247.8, 459.9, 579.7, 1573.2 at 100 mg/L for wheat flour, wheat kernels, corn, pinto bean and tobacco leaves, respectively. Pinto beans were the most sorptive commodity for EF and PPO and wheat kernels were the lowest. EF and PPO desorbed from all commodities except pinto beans 24 h after ventilation. These results may improve understanding of sorption and desorption of EF and PPO for commercial fumigations.