1 Trichloromethane
The examination method is the same as that of carbon tetrachloride in Chapter 1 of GB/T 5750.8-2006.
2 Bromoform
The examination method is the same as that of carbon tetrachloride in Chapter 1 of GB/T 5750.8-2006.
3 Dichloromonobromomethane
The examination method is the same as that of carbon tetrachloride in Chapter 1 of GB/T 5750.8-2006.
4 Chlorodibromomethane
The examination method is the same as that of carbon tetrachloride in Chapter 1 of GB/T 5750.8-2006.
5 Dichloromethane
5.1 Headspace gas chromatography
5.1.1 Scope
This Standard specifies headspace gas chromatography for determination of dichloromethane, 1,1-dichloroethane and 1,2-dichloroethane in drinking water and its source water.
The method is applicable to determination of dichloromethane, 1,1-dichloroethane and 1,2-dichloroethane in drinking water and its source water.
Minimum detectable mass concentration of this method: 9μg/L for methylene chloride, 8μg/L for 1,1-dichloroethane and 13μg/L for 1,2-dichloroethane. The minimum detectable mass concentration of the method: 9μg/L for dichloromethane, 8μg/L for 1,1-dichloroethane and 13μg/L for 1,2-dichloroethane.
Under the operation conditions of the method, other halohydrocarbons do not interfere.
5.1.2 Principle
In sealed headspace bottle, volatile halocarbon molecule escapes into the gas above the liquid surface from liquid phase; under certain temperature, halocarbon molecule reaches dynamic balance between gas and liquid phases; in this case, the concentration of halocarbon in gas phase is in direct proportion to that in liquid phase, and so the mass concentration of halocarbon in water sample may be calculated through the determination of concentration of halocarbon in gas phase.
