General Methodological Considerations

The general methodological considerations which can be drawn from the present investigation are simple to sum up. 

V. DENSITOMETRIC CHROMATOGRAM EVALUATION A. General, Methodological Considerations... 

The results of these static measurements can then be used to rate the probable usefulness of different adsorbents. However, the isotherm results from static water solutions do not apply to dynamic column situations in which equilibrium conditions may not occur. A better approach is to generate frontal breakthrough curves that can then be used to estimate the use of different polymers for different solutes dissolved in water. Theoretical and experimental reports (97, 143, 181, 286, 319-321, 537) discuss details about affinity measurements. These details are not included in this review because affinity is discussed only qualitatively in the sections on Theoretical Considerations and Generalized Methodology. These qualitative discussions suggest that neutral polymers such as the styrene-divinylbenzenes are efficient for adsorbing neutral hydrophobic solutes from water solutions but have little affinity for polar and ionic solutes. If the polarity of the polymer is increased to that of the acrylates, the affinity for neutral hydrophobic components will suffer but the more polar solutes will be better adsorbed. In the absence of actual test results under dynamic column flow conditions, the simple likes adsorb likes concept is invoked. 

Selection of a health outcome for study depends in part upon the exposure of interest and methodological considerations such as the ability to define, measure, and validate adverse outcomes, especially if self-reported. Operational definitions for outcomes can be general or specific in nature (e.g., all birth defects versus spina bifida, respectively), and will affect the type of statistical analysis which can be performed and the interpretation of results. Statistical power may be limited if restrictive operational definitions are used for rare outcomes, or if other important covariates cannot be fully addressed. 

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