Extramural Research
Presentation Abstract
Grantee Research Project Results
Adsorption of Beta-Blocker Anti-Hypertensive Pharmaceuticals to a Range of Mineral Surfaces
Rajiv Paruchuri, David A. Sabatini, and Tohren C.G. Kibbey
University of Oklahoma, Norman, OK
A wide range of pharmaceutical compounds have been identified in the environment, and their presence has been a matter of growing concern both for human and ecological health. The ultimate fate of pharmaceutical compounds in the environment can be strongly influenced by their adsorption to soils and sediments, because adsorption can slow the migration of chemicals, potentially increasing the time for degradation and reducing the potential for exposure. Adsorption behavior varies from compound to compound and can be difficult to predict for pharmaceutical compounds because their behavior is often controlled by interactions with specific functional groups or complex pH-dependent speciation. To date, only a fraction of pharmaceutical compound classes have seen extensive study of their adsorption behaviors in the presence of natural soils or sediments.
Beta-blocker anti-hypertensive pharmaceuticals are important pharmaceutical compounds for which little adsorption data exists. Beta-blockers are pharmaceuticals that are known to affect the heart and circulatory system (arteries and veins) and are used to treat hypertension. They lower the rate at which the heart beats and in turn reduce blood pressure. Beta-blockers exhibit moderately high solubilities in water and have been detected in groundwater and surface waters at μg/L levels.
The research project examines the adsorption of three beta-blockers (i.e., nadolol, propranolol, and metoprolol) to a wide range of mineral surfaces. Whole soils and sediments often are comprised of a substantial number of different minerals or mineral coatings. Adsorption to whole soils and sediments results from interactions between pharmaceutical compounds and each of the individual mineral surfaces in the whole soil, and the resulting adsorption behavior is a composite of the adsorption to each of the surfaces. The presence of multiple surface types in complex sorbents (e.g., whole soils) is one cause of adsorption nonlinearity and can result in differences in behavior as a function of concentration. A detailed understanding of adsorption requires quantitative knowledge of interactions with all of the specific mineral surfaces present. Adsorption to Canadian River Alluvium (CRA), a material collected from the alluvial channel of the Canadian River in Norman, Oklahoma, has been studied. CRA is predominantly quartz sand, with a large number of additional minerals present in small quantities. To better understand adsorption to CRA, studies were conducted on the adsorption to a high purity natural quartz sand, magnetite, hematite, ilmenite, cordierite, tourmaline, and two types of feldspars, all mineral components identified in analyses of CRA.
Results indicate that the magnitude of adsorption of each compound varies considerably from mineral to mineral on a surface-area-normalized basis. In addition, the relative magnitude of adsorption between the three compounds varies from surface to surface. This presentation will discuss the results of adsorption measurements, and implications for modeling adsorption to complex mineral surfaces. In addition, ongoing work examining the effect of surfactants on beta-blocker adsorption will be discussed.