US Patent 7790025 External gradient chromatofocusing

The invention provides novel methods for the separation of charged molecules such as proteins according to the isoelectric points (pI's) and includes the systems and buffering compositions employed for isolating charged molecules. The invention further provides for modifications to the above described chromatographic methods that enable the separation of charged molecules exhibiting virtually identical pI's by shifting both the buffer's pKa and the pI's of the eluted charged molecules while they are traversing the ion exchange column.