Gas-phase sorption-desorption of propargyl bromide and 1,3-dichloropropene on plastic materials.

ABSTRACT

The goal of this research was to provide information for choosing appropriate materials for studying gas-phase concentrations of propargyl bromide (3BP) and 1,3-dichloropropene (1,3-D) in laboratory experiments. Several materials were tested and found to sorb both gas-phase chemicals in the following order stainless steel (SS) < Teflon polytetrafluoroethylene (PTFE-FEP) approximately flexible polyvinyl chloride (PVC) approximately acrylic < low-density polyethylene (PE) < vinyl approximately silicone < polyurethane foam (PUF). Sorption of SS was insignificant and PUF sorbed all the fumigant that was applied. For the other materials, linear sorption coefficients (Kd) for 3BP ranged from 3.0 cm3 g(-1) for PVC to 215 cm3 g(-1) for silicone. Freundlich sorption coefficients for 1,3-D ranged from 11.5 to 371 cm3 g(-1). First-order desorption rate constants in an open system ranged from 0.05 to 1.38 h(-1) for 3BP and from 0.07 to 1.73 h(-1) for 1,3-D. In a closed system, less than 2% of sorbed fumigant desorbed from vinyl while up to 99% desorbed from PVC within 24 h when equilibrated at the highest headspace concentration. Sorption of both fumigants was linearly related to the square root of time except for vinyl and silicone. This may indicate non-fickian diffusion of fumigant into the polymer matrix. Vinyl, silicone, PE, and PUF should be avoided for quantitative study of organic gases, except possibly as a trapping medium. Use of PTFE, PVC, and acrylic may require correction for sorption-desorption and diffusion.