Analysis of interactions between pharmaceuticals and humic acid: Characterization using entrapment and...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Water Quality

Background:

• Pharmaceuticals are emerging microcontaminants of concern in water due to increased water reuse.
• Interactions with dissolved organic matter, like humic acid, influence pharmaceutical bioavailability and environmental impact.
• Understanding these interactions is crucial for assessing risks associated with pharmaceutical pollution.

Purpose of the Study:

• To investigate the binding strength and interactions between humic acid and common pharmaceutical microcontaminants.
• To evaluate the utility of high-performance affinity microcolumns for studying these binding processes.
• To determine the influence of environmental factors (temperature, ionic strength, pH) on pharmaceutical-humic acid interactions.

Main Methods:

• Development and use of high-performance affinity microcolumns with entrapped and immobilized humic acid.
• Examination of binding interactions for tetracycline, carbamazepine, ciprofloxacin, and norfloxacin.
• Systematic variation of temperature, ionic strength, and pH to study interaction mechanisms.

Main Results:

• Binding constants determined using Aldrich humic acid showed good agreement with literature values.
• The affinity microcolumn technique allowed for the assessment of electrostatic vs. non-polar interactions and hydrogen bonding.
• The method demonstrated rapid (minutes) and efficient quantification of pharmaceutical binding using minimal humic acid (∼10 mg).

Conclusions:

• Affinity microcolumns provide a powerful tool for screening and quantifying pharmaceutical binding to humic acid.
• This technique facilitates the study of binding mechanisms and the relative importance of different interaction types.
• The method is adaptable for a broad range of microcontaminants and binding agents in environmental research.