Hydrocarbons, halogenated ionization

A9.6.4.7 The Nordic Council of Ministers issued a report (Pederson et al, 1995) entitled Environmental Hazard Classification, that includes information on data collection and interpretation, as well as a section (5.2.8) entitled QSAR estimates of water solubility and acute aquatic toxicity . This section also discusses the estimation of physicochemical properties, including log Kow For the sake of classification purposes, estimation methods are recommended for prediction of minimum acute aquatic toxicity, for ...neutral, organic, non-reactive and non-ionizable compounds such as alcohols, ketones, ethers, alkyl, and aryl halides, and can also be used for aromatic hydrocarbons, halogenated aromatic and aliphatic hydrocarbons as well as sulphides and disulphides, as cited in an earlier OECD Guidance Document (OECD, 1995). The Nordic document also includes diskettes for a computerized application of some of these methods. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Commonly used methods for the determination of petroleum hydrocarbon contamination in soil are modifications of Environmental Protection Agency method 418.1, which use sonication or a Soxhlet apparatus for analyte extraction and either infrared spectrometry [5] or gas chromatography with flame ionization detection [6-7] for extract analysis. Regardless of the analytical method following the extraction, both modifications use Freon-113, which has been implicated as a cause of ozone depletion. Therefore, alternative methods are being sought for the determination of hydrocarbon contamination in environmental samples that reduce the need for this halogenated solvent. 

Differentiating solvents are solvents in which neither the acidity of acids nor the basicity of bases is limited by the nature of the solvent. These solvents are not self-ionized. The aliphatic hydrocarbons and the halogenated hydrocarbons are such solvents. 

Van Berkel and Zhou first tested (3-carotene with ESI positive in 1994 (van Berkel and Zhou, 1994). In this study, a doubly charged molecular ion of (3-carotene was observed as the primary species when triflur-oacetic acid was present in the solution. Van Breemen was the first to utilize ESI as an interface between HPLC and MS to analyze carotenoids (van Breemen, 1995). In this study, ESI operated in negative mode ionized xanthophylls (astaxanthin, (3-cryptoxanthin, and lutein), but did not ionize hydrocarbon carotenes (lycopene and (3-carotene). In contrast, ESI positive produced only [M" ] for all carotenoids in this study, and the addition of halogenated solvents to the post-column effluent greatly enhanced signal intensity (van Breemen, 1995). A later study by Guarantini et al. demonstrated the ability of ESI positive to produce both [M" "] and [M + H]" " for a number of xanthophylls, and these authors attributed the production of the two species to solvent system... 

G. R. Umbreit (24) has used the gas-equilibration technique to measure several halogenated hydrocarbons, employing both flame ionization detection (FID) and electron capture (EC). Halogenated hydrocarbons included dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,2,2-trichlo-... 

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