Preparative scale thin-film dialysis apparatus

A thin-film dialysis apparatus capable of processing large volumes of material is described. Dialysis casing, of defined molecular weight cutoff, is stretched on a compact frame producing a thin-film configuration. The dialysis unit is rotated by a variable speed motor with the direction of rotation periodically alternated by an electronic reversing control. This device utilizes the entire membrane area, eliminates solution stratification, and minimizes viscosity effects; membrane clogging is minimized should gelation or precipitation occur. The solutions are in contact only with the dialysis membrane; the construction materials are Teflon and polymethylmethacrylate (Plexiglas). At a load factor of 0.5 ml/cm of dialysis casing the half-time for solute removal, t1/2, for 8 M urea was 7 +/- 1 min; over 99% of the denaturant was removed in 1.5 h. The following operational factors are discussed: load capacity, rotation rate, membrane, ratio of internal to external solutions and solute contributions.