FACTORS AFFECTING SOLID-PHASE EXTRACTION OF SEMIVOLATILE ORGANIC POLLUTANTS FROM ACIDIC INDUSTRIAL EFFLUENT FOR ANALYSIS BY GAS-CHROMATOGRAPHY

A method was developed for the solid-phase extraction of toluene, chlorobenzene, xylene, dichlorobenzene and trichlorobenzene from acidic, aqueous industrial effluent, prior to quantification by gas chromatography (GC). A variety of sorbent-solvent systems were investigated and the highest analyte recoveries were obtained with a C18 sorbent and chloroform. Dichloromethane can also be used as an alternative eluent. Up to 100 ml of effluent were passed through the cartridges, containing 500 mg of C18 sorbent, without degradation of the analyte recoveries. As the analytes were completely eluted with 1 ml of chloroform, preconcentration factors of up to 100-fold were achieved. To obtain close to quantitative (100%) recovery of the analytes from samples it is necessary to prevent evaporative losses which occur (a) during storage and sampling, if a headspace is created above the liquid, (b) when sorbent drying times >2 min are used and (c) if there is a significant delay (e.g., 45 min) between drying and elution of the analytes. Accordingly, each cartridge should be loaded and eluted in series to achieve maximum recoveries. The GC method detection limits (without preconcentration) were 0.18-0.33 mug ml-1, which are adequate for the determination of the analytes at concentrations typical of the effluent studied.