1 Carbon Tetroxide
1.1 Packed column gas chromatography
1.1.1 Scope
This Standard specifies the packed column gas chromatography for the determination of trichloromethane, carbon tetrachloride, trichloroethylene, dichloromonobromomethane, tetrachloroethylene, chlorodibromomethane and bromoform in drinking water and its source water.
This method is applicable to determination of trichloromethane, carbon tetrachloride, trichloroethylene, dichloromonobromomethane, tetrachloroethylene, chlorodibromomethane and bromoform in drinking water and its source water.
The minimum detectable mass concentrations in this method are respectively: trichloromethane, 0.6μg/L; carbon tetrachloride, 0.3μg/L; trichloro ethylene, 3μg/L; Bromodichloromethane, 1μ/L;tetrachloroethylene, 1.2μg/L; Chlorodibromomethane, 0.3μg/L; bromoform, 6μg/L.
1.1.2 Principles
Put the to-be-tested water sample in a sealed headspace bottle; after certain time of balance under certain temperature, halohydrocarbon in water escape to the headspace and reaches dynamic balance in gas-liquid phase. On this occasion, concentration of halohydrocarbon in gas phase is proportional to that in liquid phase. By determining the concentration of halohydrocarbon in gas phase, the content of halohydrocarbon in water sample may be calculated.
1.1.3 Reagents and materials
1.1.3.1 Gas carrier
High purity nitrogen (99.999%).
1.1.3.2 Reagents and materials used in preparation of standard sample and sample pretreatment
1.1.3.2.1 Pure water: fresh deionized water, no determined component in the chromatogram examination.
1.1.3.2.2 Ascorbic acid.
1.1.3.2.3 Methanol: top grade pure, no determined component in the chromatogram examination.
1.1.3.2.4 Chromatogram reference materials: trichloromethane (99.92%), Bromodichloromethane (97.3%), chlorodibromomethane (98.1%), bromoform (99.73%), carbon tetrachloride (99.92%), Chlorodibromomethane (99.73%), trichloroethylene (99.53%) are all chromatographically pure.
1.1.3.3 Reagents and materials used in preparation of chromatographic column
1.1.3.3.1 Chromatographic columns and fillers: see the relevant content in 1.1.4.1.3.
1.1.3.3.2 Solvent used in coating stationary liquid: acetone.
1.1.4 Apparatuses
1.1.4.1 Gas chromatograph.
1.1.4.1.1 Electron capture detector.
1.1.4.1.2 Recorder or workstation.
1.1.4.1.3 Chromatographic column
A Type of chromatographic column: U-shaped or spired glass column. Length: 2m; inner diameter: 2 or 3mm.
B Filler:
a Carrier: Chromosorb AW or DMCS 60 meshes ~ 80meshes or 80 ~100meshes. Sieved prior to use and then baked for 2h at 120℃.
b Stationary liquid and its content: 15% DC -550(polymethyl siloxane with 25% of phenyl)
c Coating stationary liquid method: calculate chromatographic column volume, measure off carrier slightly more than the calculated volume and measure its mass. Accurately weigh a given amount of stationary liquid accordingto the mass of carrier, dissolve it in the acetone solvent, after fully dissolved, add it into carrier, and by this time liquid level shall totally immerse the carrier.At room temperature, naturally volatilize the solvent to dry (never by means of stirring with glass rod), packing may be conducted after the solvent is totally volatilized to dry and without acetone odor.
d Packing method: connect column outlet end to the vacuum pump (note : the cotton shall be plugged in the column tube), Terminate small funnel at column inlet, put in the stationary phase therefrom, carry out the column filling by air exhaust while uniform column knocking.
e Aging of chromatographic column: terminate the column inlet to the chromatographic system, empty the end at the column outlet, fill in nitrogen (flow rate: 30mL /min).Age 16h after column temperature ascends to 150℃ at the heating speed of 10℃/30min from 60℃.
