Carbon nanotube mediated microscale membrane extraction.

We demonstrate that functionalized carbon nanotubes can be readily immobilized into the pore structure of a polymeric membrane, which can dramatically improve its performance in analytical scale membrane extraction. This was accomplished by injecting an aqueous dispersion of the nanotubes through a polypropylene hollow fiber under pressure. The nanotubes were trapped and held within the pores and served as sorbents facilitating solute exchange from the donor to the acceptor phase. The effectiveness of this carbon nanotube mediated process was studied by direct solvent enrichment of nonpolar organics, and also by selective extraction of organic acids via a supported liquid membrane. In both cases, the enrichment factor measured as the ratio of concentrations in the acceptor to the donor phases could be increased by more than 200%.