Separation of Drug Traces from Water with Particular Membrane Systems

Abstract

The purpose of the present project is to examine the applicability of certain natural biological and liquid membranes for the separation of drugs of environmental concern such as ibuprofen, diclofenac, carbamazepine, and sulfamethoxazol from dilute aqueous solutions. Different types of intestine parts of cattle, sheep, and pig were applied as biological flat sheet membranes after different modes of pretreatment. Best results were obtained with special parts of cattle appendix. The concentration of each drug in the aqueous feed phase was in the range of 0.1–10 mg (cm³)⁻¹, the pH-values adjusted between 8 and 10. Pure water was used as the permeation phase. The influence of experimental parameters such as stirring velocity, temperature, pH-value, salt concentration, and the presence of surfactants as well as humic substances was studied. Under all conditions chosen the combined drugs permeate simultaneously through the natural membranes as the permeation kinetics of the individual compounds are very similar, while humic compounds were retained. Additional treatment of the permeate with liquid or solid phase extraction techniques increases crucially the depletion of the drugs from the feed. The mass transfer of the pharmaceuticals through the liquid membranes was carried out in three-compartment transport cells and supported liquid membrane-chambers. The three-phase liquid bulk membrane systems consisted of an aqueous feed solution, an organic solvent (dihexyl ether, decane, undecane, or decanol) with and without a dissolved sulfonic acid, tertiary amine or Cu(II)-chelate compound as a liquid bulk membrane and an aqueous stripping solutions containing dilute solutiuons of Na₂CO₃, NaOH, HCl, or HClO₄. The transport of the drugs shows some differences, which can be attributed to their acid/base-behavior and partition coefficients log K _ow. High extraction yields were obtained for sulfamethoxazol and carbamazepine by using polar organic solvents. Maximum transport efficiencies were obtained for the acidic compounds ibuprofen and diclofenac. They were completely extracted by using dihexyl ether loaded with octane sulfonic acid. A pH-gradient between feed and strip increases the efficiency of the transport. Certain three-phase compositions were successfully utilized in supported liquid membrane systems (SLM) so that high enrichment factors (˜75) were achieved for traces of diclofenac and ibuprofen. The solid and liquid membrane systems employed aim for technical as well as analytical purposes, such as sample pretreatment prior to HPLC-UV or LC-MS analysis of drug traces.

Keywords:

• Biological flat membranes
• Intestine
• Carrier
• Liquid bulk membranes
• Supported liquid membranes
• Pharmaceuticals
• Water treatment
• Enrichment

Acknowledgments

This work was financially supported by the Ministerium für Umweltschutz und Naturschutz, Landwirtschaft und Verbraucherschutz des Landes NRW, the Ministerium für Schule, Wissenschaft und Forschung des Landes NRW, and the Bundesministerium für Bildung und Forschung.