Microliter scale electrodialysis apparatus

A non-flowing batch eletrodialysis apparatus comprising:

• a vessel fabricated from electrically insulating material and containing anode and cathode means spaced apart horizontally;
• at least one removable, rigid unit pocket cell between said anode means and said cathode means, said unit cell open at the top and comprising at least two parallel, spaced apart electrolytically conducting barriers oriented substantially parallel to said anode and cathode means, said barriers thereby forming at least one interior liquid holding cavity in said unit cell, said liquid holding cavity being substantially narrower at the bottom than at the top, at least one of said barriers in any adjacent two barriers in said unit being ion-selective, that barrier of said adjacent two barriers having the higher transport number for cations being nearer said cathode means;
• sealing means along at least the lateral and lower edges of said unit cell to inhibit leakage of liquids between the interior of said vessel and said interior fluid holding cavity;
• support means for holding said unit cell in said vessel to orient said barriers substantially vertically and substantially parallel to said anode and cathode means;
• electrically insulating means for inhibiting bypass of electrolytic current around said unit cell when said vessel is filled with electrolyte solution to a level below the top of said unit cell and a direct electric current is applied between said anode means and said cathode means.