A method for quality screening is suggested to detect volatile impurities in inorganic coagulants that are used for drinking water treatment. Static headspace gas chromatography with mass spectrometry detection (HS-GCMS) is sensitive and selective to detect volatiles in low concentrations. This study has discovered that volatile organic impurities are detectable in ferric and aluminium-based coagulants which are used for drinking water treatment. For ferric chloride, 2-propanol was detected at a level of 17-24 microg ml(-1), acetone at 0.7-1.7 microg ml(-1), 1,1,1-trichloroacetone at 0.02-0.04 microg ml(-1), trichloromethane at 0.01-0.02 microg ml(-1) and toluene at 0.01-0.12 microg ml(-1). For ferric chloride sulfate, acetone was detected at a level of 0.12 microg ml(-1), 1,1,1-trichloroacetone at 0.06-0.08 microg ml(-1), trichloromethane at 0.13-0.23 microg ml(-1), bromodichloromethane at 0.04-0.06 microg ml(-1) and dibromochloromethane at 0.04-0.05 microg ml(-1). For aluminium hydroxide chloride, only trichloromethane was detectable, but below the method detection limits (MDL). Although the concentrations of these impurities in commercial coagulants are low, this observation is important and should have impact on water industries for them to pay attention to the chemicals they are using for drinking water production.