Determinação de clorobenzenos em lodo de esgoto por cromatografia Gasosa Aclopada a Espectrometria de Massas (CG-EM)

Abstract

Chlorobenzenes are volatile, organic and toxic compounds, persistent in the environment, with the ability to bioaccumulate in living organisms. They are present in several environmental matrices, among them the sewage sludge. The extraction of these contaminants in the sludge is commonly performed by sohxlet extraction technique, which is standardized for analysis of organic compounds. This technique is satisfactory; however, it is laborious with high solvent consumption. Thus, this work performed the optimization, validation and application of the solid-liquid extraction with purification at low temperature technique for the analysis of nine chlorobenzenes in sewage sludge. This extraction method is promising because it is practical and economical. Analyses were performed by gas chromatography coupled with mass spectrometer detector. After univariate optimization of the extraction phase, which consisted of acetonitrile, ethyl acetate and dichloromethane, a factorial design was used to evaluate the influence of pH, ionic strength and homogenization time. Then, heating time for the extraction of the compounds was optimized. During the validation step, the method proved to be selective, with limits of detection and quantification lower than 4.1 g kg-1 and 12.5 g kg-1, respectively. Extraction percentages were about 70% with relative standard deviation inferior to 12.97% for all chlorobenzenes analyzed. The results obtained after optimization of the method were efficient if compared to the reference techniques (soxhlet extraction). The SLE-PLT was applied to real samples of sludge to monitor chlorobenzenes for a period of 11 months. During this period, two types of chlorobenzenes were detected in most samples.