Partitioning and Accumulation of Selected Basic Pharmaceuticals in Natural Organic MatricesEPA Grant Number: F07E10138
Title: Partitioning and Accumulation of Selected Basic Pharmaceuticals in Natural Organic Matrices
Investigators: Fallert, Kari L.
Institution: Oklahoma State University
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2007 through January 1, 2010
RFA: STAR Graduate Fellowships (2007) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Aquatic Systems Ecology , Aquatic Ecology and Ecosystems
Although partitioning coefficients such as water-sediment and octanol-water are commonly used to evaluate environmental fate of chemical contaminants, limited previous research has examined differential partitioning between various types of organic matter found in streams. This study will examine the partitioning of a series of environmental contaminants, with specific emphasis on basic pharmaceuticals, to various natural matrices, including fine particulate organic matter (FPOM), coarse particulate organic matter (CPOM), sediment, periphyton, and aquatic biofilm. If differential partitioning occurs, potential implications include: matrices which have the highest degree of partitioning could be used as biomarkers during environmental assessments, remediation techniques could be improved, and assessment of exposure may be enhanced. In addition, the mechanism of differential sorption will be examined including the possibility that a combination of sorption mechanisms, such as cation exchange and hydrophilic-hydrophobic interactions, are responsible.
A series of basic pharmaceuticals, that are potential environmental contaminants, will be evaluated including propranolol, ciprofloxacin, sertraline, and nicotine. Partitioning of the compounds between water and environmental matrices will be determined utilizing batch experiments with a variety of matrices that occur in aquatic systems. Initial studies will utilize leaf discs for the CPOM, amphipod processed leaf material for FPOM, and biofilm collected on glass beads placed within natural aquatic systems. Secondary studies will collect matrices from stream and wetland sites.
Radiolabeled compounds (14C and 3H), when available, will be used to quantify the amount of analyte in both aqueous and solid matrices. Otherwise, extraction and chromatographic analysis will be conducted. Partitioning coefficients will then be calculated. Several secondary factors such as the influence of concentration and pH will be evaluated. In order to determine the primary mechanism of sorption and if mixed mechanisms of sorption increase partitioning, the affinity of each compound to cation exchange resins and octanol (KOW) will be determined.
Based on preliminary data, it appears differential sorption among matrices is likely. Our hypothesis is that the effect will be greatest for weak organic bases, moderate for polar organics, and limited for nonpolar organics. Since many pharmaceuticals are weak bases, differential partitioning is likely to be a major factor in the fate assessment of many classes of pharmaceuticals. Overall, this research will provide an initial assessment of the degree of differential partitioning that may occur among aquatic matrices and whether more detailed partitioning estimates are necessary to adequately assess the risk of organic contaminants.