Abstract
A solid sorbent sampling and analytical method for chlorine (Cl2) and bromine (Br2) in air, based on the reaction of halogen gases with silver to form silver halides, has been developed. The sampler uses an opaque, 25-mm cassette containing a Zefluor™ or polyester prefilter and a cleaned silver membrane filter. The silver halides are complexed with thiosulfate, releasing the halide ion, which is determined by ion chromotography. The method was laboratory evaluated using generated test atmospheres (room temperature, 20% and 80% relative humidities, and concentration levels of 0.1 to 2 times the Permissible Exposure Limit [PEL] set by the U.S. Occupational Safety and Health Administration [OSHA]), and field evaluated at a chlorine-containing industrial environment. Precision of the method was 7.2 percent, and the bias was insignificant (-1.3%). High humidity (∼80%) dramatically increased the capacity of the silver filter for Cl2 and Br2. Hydrogen chloride is a minor positive interference; however, hydrogen bromide presents a more significant interference. The method has the sensitivity to monitor Cl2 at the current OSHA time-weighted average (TWA) PEL of 0.5 ppm and short-term exposure limit (STEL) of 1 ppm, as well as the TWA for Br2 of 0.1 ppm and the STEL of 0.3 ppm.