In this paper, the technique of solid-liquid extraction with purification at low temperature for the determination of nine chlorobenzenes (CB) in sewage sludge was optimized, validated and applied. Analyses were carried out by using gas chromatography coupled with mass spectrometry. After univariate optimization of the extraction phase, a factorial design was used in order to evaluate the influence of pH, ionic strength (NaCl) and homogenization time. The method proved to be selective, with detection and quantification limits less than 4.1 and 12.5 µg kg-1, respectively. Recoveries were about 70% and the relative standard deviation was less than 13% for the chlorobenzenes analyzed. During the monthly monitoring of sewage sludge samples 1,4-CB, 1,2,4-CB and 1,2,3-CB were detected. Only 1,2,3-CB was quantified in concentrations higher than the maximum acceptable limit for chlorobenzenes in agricultural soils amended with sewage sludge disregarding the dilution effect of the sludge on soil.
biosolids; chlorobenzenes; extraction methods
