Salts and small molecules can be removed from protein samples by gel filtration chromatography. When added to the column, small molecules have to travel through the extensive pores of the resin beads, while large macromolecules like proteins can't fit and therefore travel around them. This allows the larger molecules to flow through the column at a faster rate than smaller molecules that have to traverse through the resin. Thus, the desalted proteins can be separated and collected.