A Diffusive Sampler for Gaseous Chlorine Utilizing an Aqueous Sulfamic Acid Collection Medium and Specific Ion Electrode Analysis

Abstract

A diffusive sampler for chlorine gas which uses microporous membranes and a liquid collection medium was developed. The device is constructed from a 37-mm, polystyrene aerosol filter cassette and uses two Teflon® filters in series, 11 mm apart, as diffusion membranes. The inner filter is in contact with approximately 7 ml of aqueous 0.1 percent sulfamic acid solution. The outer filter acts as a wind screen. Collected chlorine is determined with a residual chlorine-specific ion electrode. The mass transfer constant of the sampler for chlorine is 9.38 μg/ppm-hour at 25°C, with the mass transfer rate being linear up to at least 20 ppm-hour of exposure dose. The lower limit of detection for the monitor is estimated to be 0.1 ppm-hours, less than 3 percent of the current Occupational Safety and Health Administration Permissible Exposure Limit of 0.5 ppm for 8 hours of exposure. Sampler response becomes essentially constant at wind speeds above 12.7 cm/s. The response is independent of humidity while the collection rate decreases with temperature at a rate of 0.05 μg/ppm-hour per degree Celsius. The simplicity and performance of the device make it particularly suited to large-scale surveys of exposure to chlorine in the workplace.