Aliphatic halogen compounds, determination

Aliphatic halogen compounds, determination of 282,283,350,35h 369 Aliphatic hydrocarbons, determination of 273-275 Alkali earths, determination of 40,43, 46, 47,91-94... 

There has been a growing interest in applying high performance liquid chromatography, to the determination of the not only volatile compounds, such as aliphatic and polyaromatic hydrocarbons, saturated and unsaturated aliphatic and polyaromatic hydrocarbons, saturated and unsaturated aliphatic halogen compounds, haloforms and some esters, phenols and others but also non volatile components of water. 

Other applications of gas chromatography to the determination of haloforms and aliphatic halogen compounds in non saline waters are discussed in Table 15.9. 

The compounds are representatives for different types of pollutants. 11 halogenated aliphatic hydrocarbons are determined using capillary GC equipped with electron capture detector. The remaining pollutants, representing both basic/neutral and acidic compounds are determined using GC/MS combined with an automated search computer program. 

S Halogenated Compounds Many halogenated compounds, either because of their extensive use or their persistence are of environmental interest. The smaller, halogenated aliphatics have been used extensively and are common ground water contaminants," while the persistence of the PCBs and chlorinated dibenzo dioxins is well documented. Hydroxyl radicals are the more important oxidants in the vapor phase and the hydrocarbon structure determines the nature of the reaction. Second-order rate constants for some of these compounds are summarized in Table 6.27. 

Kester [191] has reviewed the application of this technique to the determination of a wide range of organic compounds in soil, including ketones, aldehydes, aromatic hydrocarbons, halogenated aliphatic compounds, alcohols and vinyl acetate. 

The application of the displacement of halogen by nickel-aluminum alloy in aqueous alkali to the quantitative determination of halogens in organic compounds (115) is of considerable interest. Many of the above methods, when adapted for analysis, require the use of hydrogen gas, a prepared catalyst, and a hydrogenation apparatus of the conventional type. These requirements are obviated by the use of nickel-aluminum alloy in aqueous alkali, and the method is advantageously used for the quantitative determination of halogen in many aliphatic, aromatic, alicyclic, and heterocyclic compounds. 

The widespread contamination of surface and groundwaters by halogenated aliphatics has prompted efforts to determine pathways for the degradation of these environmental pollutants. Hydrolysis half-lives for halogenated aliphatics range from months to years however, because residence times for these pollutants in groundwater systems are often measured in years, hydrolysis will be an environmentally significant transformation pathway for these compounds. 

Treatment with sulfuric acid or concentrated base offers an alternative solution for the removal of lipids and other interferences. Because PCBs are generally resistant to sulfuric acid, concentrated sulfuric acid treatment is used for degradation of most aliphatic and many aromatic compounds in environmental samples. Sulfuric acid may affect other compounds such as some halogenated pesticides (e.g., dieldrin) that are determined together with PCBs in one extract. 

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