Could you please indicate me (strong or weak) anion or cation exchange LC columns that have been used or can potentially been used for protein separation?

Thanks

Columns designed for this purpose usually have a larger pore size distribution. You can check at the website of Waters (www.waters.com). All four packings are available.

Another option is nonporous media. Dionex sells a family of nonporous ion exchange materials (both strong and weak in both anion and cation versions) which provide exceptionally high resolution of proteins. In addition, Amersham, Merck and Tosoh also have products in this arena.