Analysis of chlorobenzenes in sewage sludge by capillary gas chromatography

Abstract

An analytical method has been developed to investigate the occurrence of chlorobenzenes in sewage sludge. Sewage sludge was centrifuged, dewatered, Soxhlet extracted, cleaned and analysed by capillary gas chromatography using two columns with different polarity, DB Wax and Ultra-2. The effects on the recovery of chlorobenzenes were examined using different solvents, drying techniques and Soxhlet extraction times. All of the chlorinated benzenes eluted within thirty minutes from both of the capillary columns. Recoveries of these compounds by this procedure were all greater than eighty percent (except for monochlorobenzene) at two concentrations while the coefficient of variation, %C.V., is less than 10%. The detection limits of this method are 5–10 μg/kg (dichlorobenzenes), 0.6–1 μg/kg (trichlorobenzenes), 0.5 μg/kg (tetrachlorobenzenes) and 0.3–0.4 μg/kg (penta- and hexachlorobenzene) when using approximately 1 gram (dry weight) sample. Sewage sludges from municipal and industrial areas have been analysed by this method and the significance of these compounds in sewage sludge discussed.