Determination of 1,2,4-and 1,3,5-trichlorobenzenes in water samples by solid-phase extraction and gas-chromatography coupled to electron capture

Gas chromatography of 1,2,4-trichlorobenzene and 1,3.5-trichlorobenzenes in water samples has been performed after adsorption from 80-mt sample on to a cartridge containing 200 mg cyanopropyl-bonded porous silica. The two trichlorobenzenes are desorbed with 500 muL carbon disulfide or pentane, which is concentrated and analysed by gas chromatography with electron-capture detection (GC-ECD). The recovery of 1-15 ppb trichlorobenzenes from distilled water and from Aniene and Tiber river water samples is greater than or equal to 90% (standard deviation less than or equal to 5.5). The limit of detection is 0.02 ng mL(-1) and 0.03 ng mL(-1) for 1,2,4-trichlorobenzene and 1,3,5-trichlorobenzene (standard deviation less than or equal to 9), respectively. The method described is fast. simple and reproducible.