Electrophoresis in fused salts

This category of separations is done on glass fibre asbestos or quartz papers, on thin layers or in columns [80-84]. In any case the support and equipment used must withstand high temperature. All materials must be purified before electrophoresis in order to remove impurities and to ensure better wettability by the melted salt  

The procedure itself is materialized in a special tank made of Pyrex glass (Fig. 

The whole apparatus is placed into a thermostatted furnace which is being washed with neutral gas in order to remove products of electrolysis. The electrodes are made of metals which can withstand the drastic conditions of the procedure, platinum for the anode and tungsten, nickel, copper or graphite for the cathode. The impregnated support (fibreglass paper) is equilibrated for about 1 h with the molten salt before the actual electrophoresis. The sample is applied from a capillary that can be moved from the outside of the furnace. 

The electrolytes used here are mainly nitrates and chlorates of alkaline metals or their eutectics in order to achieve low melting points. The procedure is applied mostly to the estimation of electrophoretic mobilities of inorganic anions and cations and for the separation of isotopes. Of theoretical interest is the fact that electro-osmotic flow in molten salts is practically negligible because of the small electric double layer at the temperatures used. 

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Fig. 6.8. Cross-sectional view of apparatus for electrophoresis in fused salts, (a) Electrophoresis chamber (b) Pyrex glass plate (c) Pyrex vessels (d) glass fibre paper (e) capillary with a screw to move it in all directions (0. furnace with heating and temperature regulating system g.i., gas inlet tube g.o., gas outlet tube.

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