Hydrocarbons highly volatile halogenated

ISO 10381-2 (1994) Soil quality - Sampling - Part 2 Guidance on the design of sampling techniques. ISO 10381 (1997) Water quality - Determination of highly volatile halogenated hydrocarbons - Gas-chromatographic methods. 

For the determination of highly volatile halogenated hydrocarbons, the GC-MS technique has not been included explicitly in the principles of EN ISO 10301 (EN/ISO, 1997d), so reference is made to the ECD-technique. 

Systematic determination of highly volatile halogenated hydrocarbons (HHC) in water samples using gas chromatography... 

Fig. 134. Chromatograms of highly volatile halogenated hydrocarbons on two columns with different polarity 1) = Dichloromethane 2) = Chloroform 3) = Carbon tetrachloride 4) = 1,1,1-trichloroethane 5) = Trichloroethene ...

The electron capture detector is especially suitable for halogen, sulfur, and nitro-compounds, i.e., compounds that are able to capture electrons. Because of its high selectivity and sensitivity, it is much used for residue analysis, e.g. for volatile halogenated hydrocarbons and plant protection agents. Figure 4-2 shows the design of an ECD. 

Volatile organic compounds (VOC) contribute to the formation of tropospheric ozone (summer smog). Certain halogenated hydrocarbons (e.g. CFCs) also destroy the stratospheric ozone layer. Chlorinated solvents are hazardous to water and, if disposed of incorrectly (e.g. burning), may emit highly toxic substances (e.g. dioxins). 

The uncontrolled spread (dispersion) of organic chemicals results from their mobility (determined by their chemical structure), the nature of their applications and the physicochemical conditions at the place where they are used. Increasing concentrations of halogenated hydrocarbons in the atmosphere would be impossible without the high volatility (vapour pressure) of these substances. Similarly, bioaccumulation factors of up to 100 000 (PCBs in oysters) (Fbrstner, 1995) can only occur because the chemicals concerned are highly lipophilic and the equilibrium of their distribution between water and fat is very much on the side of the solution in fat. 

Colorless liquid with a sharp, unpleasant smell highly volatile bp 39°C (102°F) mp -80°C(-112 F) density0.96at20°C(68°F) soluble in hexane, isooctane, chloroform, methylene chloride, and other hydrocarbons or halogenated hydrocarbons it decomposes in water. 

For the general separation of volatile heilogenated hydrocarbons a column should be used with a high retention. Since the halogenated hydrocarbons do not have a bonded group capable of hydrogen-bond formation, they can be analyzed on virtually siny type of stationary phase giving symmetrical peeiks. The most favored phases are the chemically bonded methylphenylsiloxanes with a film thickness of 1 -3 urn. 

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