Complex Mixtures Methods for In Vivo Toxicity Testing (1988) / Chapter Skim
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4. Sampling and Chemical Characterization
4. Sampling and Chemical Characterization
Pages 65-98
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From page 65... ...
Once the mixture has been partially defined, sampling techniques, bioavailability, and chemical characterization can be considered. In light of the understanding that complex mixtures can vary widely from combustion and distillation products of fossil or synthetic fuels, to pyrolysis products of tobacco or synthetic materials in buildings, to components leaking from waste-dump sites some criteria must be identified for the mixture, re65
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From page 66... ...
If one knows the origin of a sample, one can deduce qualitative and quantitative information about the mixture in question, even if physical characterization and chemical characterization are minimal. Extensive information on chemical characterization of a series of fossilfuel-related materials has been published (e.g., Wright and Dauble, 19861.
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From page 67... ...
, a carcinogenic polycyclic aromatic hydrocarbon (PAH) , from particles collected during high-volume atmospheric sampling (De Wiest and Rondia, 19761.
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From page 68... ...
Spatial Considerations Inclusion of spatial considerations in the sampling design requires the advice of experts, including industrial hygienists, engineers, and biostatisticians. The primary consideration should be the relevance of the sample site to potential human exposure.
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From page 69... ...
The population or study site is divided into as many strata as appropriate, and simple random sampling is applied to each stratum. Another technique is multistage subsampling, which involves division of the site or population into primary units (Cochran, 19771.
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From page 71... ...
The location of each sample is then chosen by applying a grid of fixed dimensions over the chosen area, and two random coordinate numbers are drawn to fix the location of the original point. Each sample site is then fixed in relation to this original point.
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From page 72... ...
(19841. Gases and Aerosols Vapor-phase organic chemicals have been collected from ambient air, combustion exhaust gases, cigarette smoke, and indoor spaces for chemical characterization and bioassay (Hanson et al., 1981 , 1984; Griest et al., 1982; Higgins et al., 1983; Pellizzari et al., 1976; Pellizzari, 1982; Hughes et al., 1980; Krost et al., 1982~.
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From page 73... ...
, whereas other chemical transformations reportedly have increased mutagenicity (Clark et al., 19811. Point-source sampling for air particles includes use of impactors (Cheng and Yeh, 1979)
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From page 74... ...
Altering the pH of a mixture of materials, however, also results in changing its chemical composition or biologic activity. Aqueous samples with large amounts of suspended solids are generally best prepared by separation ofthe phases.
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From page 75... ...
Solvents used for extracting materials from soil matrices for chemical analysis have included the following: benzene, ethyl acetate, and benzene-methanol-acetone (2: 1: 1) for humic substances (Ogner and Schnitzer, 1970; Cifrulak, 19691; n-pentane, carbon tetrachloride, and methylene chloride for oil (Jobson et al., 1974; Jensen, 1975; McGill and Rowell, 1980~; and hexane-isopropanol (3:1)
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From page 76... ...
Mechanisms must be instituted at each step of sample handling to ensure that the material collected is the material tested. Balanced against this need to maintain sample integrity is the need to deliver the sample to the bioassay appropriately.
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From page 77... ...
For less complex mixtures of similar substances, such solvents as dimethyl sulfoxide, ethanol, methanol, acetonitrile, or methylene chloride might be adequate for most chemical or toxicologic studies. More complex mixtures (coal tar or liquids derived from coal liquefaction)
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However, these internal standards should be carefully selected, because they might interfere with the anticipated bioassay. ANALYSIS The following discussion on chemical characterization of complex mixtures presents highlights of past and current analytic strategies and techniques.
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From page 79... ...
Although this type of chemical classification limits the number of classes, irrespective of the degree of complexity of the mixture in question, it permits the chemical and toxicologic aspects of the research to be interactive, in that only one chemical nomenclature needs to be used. GENERAL CONSIDERATIONS IN FRACTIONATION OF COMPLEX MIXTURES Many approaches have been used for analyzing complex mixtures.
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From page 80... ...
or to predict toxicity, some fundamental information is needed in designing chemical characterization experiments. Consideration should be given first to the total quantity of material (mass)
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From page 81... ...
Separation and purification of the constituents are necessary because it is rarely possible to identify the constituents of a mixture directly. Separation of the constituents of a mixture should be quantitative for both bioassay and chemical characterization.
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From page 82... ...
Adsorption Solvent-solvent; solvent-acid/base Partition Molecular exclusion Ion-exchange High-performance liquid (HPLC) Adsorption Partition Molecular exclusion Ion-exchange Organic solvents of different polarity; aqueous acid/base solutions Aluminum, silica gel, polyamide, Florisil Cellulose Porous polymers, gels Ion-exchange resins (anionic, cationic)
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From page 83... ...
There might tee a lack of additivity in a fractionated complex mixture, because of the loss of toxic analyses, because chemical reactions transform toxic analyses to nontoxic substances (or vice versa) , or because of the nature of the assay itself.
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From page 84... ...
Chromatography with alumina, Florisil, XAD-2, Ambersorb, and silica gel has been evaluated for separating organic substances from drinking water
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From page 85... ...
, diesel particulate extracts (Pederson and Siak, 1981; Pederson, 1983) , and other complex mixtures.
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From page 86... ...
High-resolution gasliquid chromatography is often used in combination with a detector that yields molecular information (e.g., mass spectrometer and Fourier-transform infrared spectroscopy)
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From page 87... ...
Detectors that have been successfully coupled to SFC include ultraviolet-absorption, fluorescence, flame-ionization, and nitrogen thermoionic detectors, as well as mass spectrometry. The available methods of separating complex mixtures are HPTLC, SFC, field-flow fractionation, electrophoresis, electroosmosis, and isoelectric focusing.
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From page 88... ...
Extreme caution should be exercised when one is comparing chemical data bases derived from different complex mixtures, because the separation techniques introduce uncertainty as to whether structural elucidation is unequivocal or merely postulative or tentative. For structural analysis, these modern methods are used most efficiently if they are combined, because they can provide complementary information that increases their overall effectiveness.
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From page 89... ...
The exquisite sensitivity of GC/FT-IR with matrix isolation rivals that of mass spectrometer; these two methods can also be combined to provide simultaneous and complementary information during chromatography of a complex mixture. The gas chromatograph is the most commonly used inlet system for analysis of complex mixtures with mass spectrometry (Watson and Throck, 19851.
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From page 90... ...
1984. Toxicological and chemical characterization of the process stream materials and gas combustion products of an experimental low-Btu coal gasifies.
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From page 91... ...
1984. Development and Evaluation of Supercritical Fluid Chromatography/Mass Spectrometry for Polar and High Molecular Weight Coal Components.
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From page 92... ...
1983. Summary of chemical characterization methodologies with future directives, pp.
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1980. Chemical characterization of polynuclear aromatic hydrocarbons in airborne effluents from an experimental fluidized bed combustor, pp.
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1980. Ambient air pollutants: Collection, chemical characterization and mutagenicity testing.
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1984. Capillary column gas chromatographic separation of amino polycyclic aromatic hydrocarbon isomers.
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1984. Chemical transformations during ambient air sampling for organic vapors.
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From page 97... ...
1983. Biodirected chemical characterization of synfuel materials, pp.202-214.
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From page 98... ...
1984. Approaches and applications of supercritical fluid chromatography and supercritical fluid chromatography-mass spectrometry techniques.
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