Evaluation of head space technique for the determination of trihalomethanes in water

Results are presented from studies on the effects of temperature, pH value, and presence of reducing agents on the determination of several trihalomethanes (THM) in water by the headspace method. In general, recovery of the compounds increased with increase in temperature up to 60C, and was reduced when sulphur compounds (sodium thiosulphate or sodium sulphite) were used to pressure the samples. The optimal pH value was 7.0. Quality-control samples were used to assess the precision and recovery of the technique, and confirmed that the head-space procedure was sensitive and simple to use, requiring no pre-concentration of the sample. The mean standard deviation for all samples was in the range 6-9 per cent, with recovery in the range 89-104 per cent.