Abstract: The determination of trichlorobenzenes (TCBs) in water-based cutting fluids and wastewater of machining has been carried out. A gas chromatography/mass spectrometry (GC/MS) method with selected ion monitoring (SIM) mode was employed. The target analyte was extracted from the matrix using dispersive liquid-liquid microextraction. Comparing with gas chromatography/electronic capture detection (GC/ECD) coupled with traditional sample preparation procedures, e.g. head-space extraction, liquid-liquid extraction and solid-phase extraction, the present method was accurate with broader linear range, better enrichment property, better replicability, easier to be operated and less interference. Overall recoveries were 94.7%-104.3% with the relative standard deviations （RSDs） of at 2.3%-7.8%. The detective limits for 1,3,5-, 1,2,4- and 1,2,3-trichlorobenzene were 2.0, 6.0 and 3.0 μg/L, respectively. The parameters, such as the nature and volume of extraction solvent, dispersive solvent, extraction time and salt effect, were studied and optimized. Some important factors, e.g., the concentration of common used additives in water-based cutting fluids, which may affect the recoveries and replicabilities for the determination of trichlorobenzenes, have been investigated. The result showed that no significant effects have been observed when the concentrations of NaNO2 and polyethylene glycol （PEG） were up to 1.0 %. The present method has been applied for the determination of the trichlorobenzenes in 4 real samples. The result showed that two of them were found to contain these trichlorobenzenes. The TCBs in the samples were 0.15-1.67 mg/L.

Key words: gas chromatography/mass spectrometry (GC/MS), trichlorobenzenes (TCBs), wastewater of machining , water-based cutting fluids, dispersive liquid-liquid microextraction