Hexachlorobenzene (HCB) is a chlorinated organic compound with moderate volatility. It is practically insoluble in water, but is highly lipid-soluble and bioaccumulative. Technical grade HCB contains up to 2% impurities, most of which is pentachlorobenzene. The remainder includes the higher chlorinated dibenzo- p-dioxins, dibenzofurans and biphenyls. Analysis of HCB in environmental media and biological materials generally involves extraction of the sample into organic solvents, often followed by a clean-up step, to produce organic extracts for gas chromatography/mass spectrometry (GC/MS) or gas chromatography with electron capture detection (GC/ECD).