Collection of Airborne Free Chlorine on a Bromide/2,6-Dimethylphenol-Coated Solid Sorbent with Chromatographic Determination

Abstract

A new solid sorbent has been developed that is suitable for personal monitoring of exposure to chlorine. The sorbent was prepared from silica gel coated with 2,6-dimethylphenol (DMP), sodium bromide, and sulfuric acid. Chlorine oxidizes bromide to bromine, which then brominates DMP to form 4-bromo-2,6-dimethylphenol (BDMP) through electrophilic aromatic substitution. The direct reaction of chlorine with DMP to form 4-chloro-2,6-dimethylphenol was found to be unsuitable due to competing reactions. BDMP was desorbed with methanol and determined by gas chromatography (GC) with flame ionization detection or high-performance liquid chromatography (HPLC) with ultraviolet absorbance detection. Recovery of collected chlorine as BDMP was quantitative from 0.05 to at least 2 ppm for 20-L air samples, and precision and accuracy were within National Institute for Occupational Safety and Health guidelines. Limits of detection for a 20-L air sample were approximately 10 ppb chlorine, when analyzed by either GC or HPLC. Humidity had no effect on recovery of chlorine or capacity of the sorbent. Collected samples were stable at room temperature for up to 7 days with losses of about 9 percent occurring after 14 days. The strong oxidizing agents, ozone and chlorine dioxide, were severe interferants, reacting as equimolar amounts of chlorine. Nitrogen dioxide was a mild positive interferant, reacting as less than 10 percent of an equivalent amount of chlorine. This unique sorbent offers a practical and sensitive method for measuring airborne concentration of chlorine. Rando, R.J.; Poovey, H.G.: Collection of Airborne Free Chlorine on a Bromide/2,6-Dimethylphenol-Coated Solid Sorbent with Chromatographic Determination. Appl. Occup. Environ. Hyg. 8(2):126-133; 1993.