A simple microtechnique for isoelectric focusing on a density gradient.

Isoelectric focusing in a density gradient can be performed on chromatographic columns of 10–15-ml volume. A polyacrylamide salt bridge was used to make electrical contact between the density gradient tube and the electrode compartment. An appropriate gradient mixer can easily be made from two 10-ml syringes. The small column permits a resolution of isoenzymes which is comparable to the separation with a commercial 110-ml column.With the described apparatus one uses ten times less Ampholine and biological sample. The time of isoelectric focusing is reduced three to four times.