Microfluidic pervaporation of ethanol from radiopharmaceutical formulations

A pervaporation process was implemented into microfluidic chips to purify radiopharmaceuticals for Positron Emission Tomography in continuos-flow. The chip consists of a serpentine microreactor interfaced to a polydimethylsiloxane (PDMS) 10 mu m thick membrane. Thanks to different volatility of the components present in the radiopharmaceutical matrix, ethanol (EtOH) is readily removed under gentle heating and nitrogen flow conditions. Three classes of chips with different membrane surface areas (S) and internal volumes (V) have been produced and quantified their pervaporative efficiency at different residence times (R-t) and temperatures. Higher S/V chips (70 mm(-1)) apperared the most efficient at a very low residence time (R-t similar to 10s) allowing reduction of 67% at 80 degrees C. Chips of intermediate S/V ratios (30 mm(-1)) decreased the EtOH amount up to 90% at longer residence time (R-t >= 26 s). The halving of EtOH concentration in a solution of a radiotracer was obtained at 50 degrees C with R-t of 25 s. After the pervaporation treatment, the EtOH content in the final radio pharmaceutical formulation was demonstrated to be reduced below 10% v/v as required by the European Pharmacopea current edition.