What method can be employed to separate proteins based on size after SDS-PAGE?

The method that effectively separates proteins based on size following SDS-PAGE is gel filtration chromatography. This technique relies on the use of porous beads within a column, allowing smaller molecules to enter and be temporarily retained within the beads, while larger molecules pass through more quickly. Therefore, as the mixture is eluted from the column, proteins elute in order of size, with the largest ones showing up first.

Western blotting, while it is a crucial technique for detecting specific proteins after they have been separated by SDS-PAGE, does not involve the separation of proteins based on size. Instead, it focuses on transferring the proteins to a membrane and probing for specific antigens using antibodies.

Total protein quantification measures the overall concentration of proteins in a sample but does not separate them based on size.

Isoelectric focusing is a method that separates proteins based on their isoelectric point rather than their size. While it is a valuable technique in protein analysis, it does not relate to the size-based separation that follows SDS-PAGE.

Thus, for separation by size specifically after SDS-PAGE, gel filtration chromatography is the appropriate method.