Session: Advances in Separations:

There is an urgent need for the development of methods that can examine the reversible chemical interactions which exist between antibiotics and dissolved organic matter in environmental water samples to help understand the transportation, solubility, and activity of antibiotics in the water samples. This study focuses on the development of a chemical analysis method based on flow-through humic acid columns to study the interactions of antibiotics and the dissolved organic matter, humic acid. The stationary phase was prepared by immobilizing humic acid on a porous HPLC support such as diol-bonded silica which has dihydrazide groups on its surface using a non-covalent entrapment method in presence of mildly oxidized glycogen. A pH 7.4 potassium phosphate buffer was employed as the application and elution buffer for all the chromatographic studies to mimic the binding conditions for the system under investigation. The interaction between humic acid and tetracycline was studied by injecting a small amount of the drug onto the humic acid column and the retention time and peak variance of the drug inside the column was monitored using an on-line absorbance detector. Experimental parameters such as the concentration of humic acid and humic acid-to-silica weight ratio were optimized and the effect of these parameters on the association equilibrium constant, K_a, and dissociation rate constant, k_d for the tetracycline-humic acid interactions was studied. The information obtained from this method can be useful in understanding how drugs interact with humic acid when they are circulated in environmental waters.

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