Membrane pertraction of Lu(III) with di(2-ethylhexyl) phosphoric acid as a carrier

Introduction: In a supported liquid membrane (SLM) extraction, also named pertraction, target analytes are extracted from an aqueous feed sample, the ‘donor phase’, into an organic phase entrapped in micropores of a hydrophobic support membrane, and further transferred into an acceptor phase. Different approaches and applications of SLM extraction are described in scientific literature such as analysis of drugs, pesticides, metal ions, organic pollutants1 etc. Though a number of SLM extraction investigations on metal ion separation have been reported in literature2, very little work has been doneon the application of membrane extraction for radionuclide separation3,4. Radiopharmaceuticals are drugs labeled with radionuclide which are used in various diagnostic and therapeutic applications in nuclear medicine. The interest for the usage of radiolabeled peptides and monoclonal antibodies for therapy is growing in the last decade. Also, radioactive isotope 177Lu and labeled radiopharmaceuticals are being increasingly used as therapeutic agents in nuclear medicine5. Although the percentage of binding the radionuclide to a target molecule is usually very high (~ 98%), there is always a fraction of the free radionuclide. This is very important in the case of radiopharmaceutical for radiotherapy. The single dose for radiotherapy can be very high (up to 30 GBq), thus the absolute amount of free radionuclide can be significant. The free 177Lu(III) accumulates in bones, thus is very important to separate free 177Lu(III) from the labeled compound. The most commonly applied technique for this purification is chromatography. Except that, the application of SLM extraction with flat membrane for separation labeled compound and free 177Lu(III) was proposed and studied in our previous paper4. Recently, SLM extraction has been simplified by introduction of a SLM extraction in a single hollow fiber without any special device6. The SLM extraction in a single hollow fibre can be operated only in a batch mode without any phase flow rate. Apart from common characteristics of membrane extraction such as large interfacial areas, low consumption of organic solution, good opportunity for process automation etc, SLM in a single hollow fibre has additional advantages such as easy to handle equipment, no special device to avoid accidental release of radioactive material and a sample volume as low as 1 cm3. The aim of the present study was to investigate the pertraction of Lu(III) from an aqueous phase by applying miniaturized SLM extraction in a single hollow fibre. The influence of the donor pH, content of the carrier in the organic phase and the time of extraction on lutetium extraction and stripping were investigated.