Determination of volatile halogenated organic compounds in soils by purge-and-trap capillary gas chromatography with atomic emission detection

Nine volatile halogenated organic compounds (VHOCs), including four trihalomethanes (THMs), were determined in soils by capillary gas chromatography with microwave induced-plasma atomic emission spectrometry (GC-AED), using a purge-and-trap system (PT) for sample preconcentration. Analytes were previously extracted from the soil sample in methanol and the extract was preconcentrated before being chromatographed. Element-specific detection and quantification were carried out monitoring two wavelength emission lines, corresponding to chlorine (479 nm) and bromine (478 nm). Each chromatographic run took 21 min, including the purge step. The method showed a precision of 1.1–7.2% (R.S.D.) depending on the compound. Detection limits ranged from 0.05 to 0.55 ng ml−1, for chloroform and dichloromethane, respectively, corresponding to 3.3 and 36.0 ng g−1 in the soil samples. The chromatographic profiles obtained showed no interference from co-extracted compounds. Low levels of dichloromethane and chloroform ranging from 0.04 to 1.13 μg g−1 were found in samples obtained from small gardens irrigated with tap water. The method is reliable and can be used for routine monitoring in soil samples.