For over 50 years, Waters has been the market leader in LC-based GPC and SEC analysis, providing the highest quality columns and applications support for both organic- and aqueous-based size separations. The names gel-permeation chromatography (GPC), size-exclusion chromatography (SEC), and gel filtration chromatography (GFC) are commonly used terms to describe a liquid chromatographic technique that separates compounds based on their relative different sizes in solution. This isocratic-based separation is performed by injecting sample onto a carefully packed column(s) containing particles of defined pore size with the larger molecular weight species eluting before those compounds of smaller molecular weight (i.e., larger sized species elute prior to smaller sized compounds). Chromatographers with different backgrounds and application needs tend to refer to these same size-based separations by different terms. In general, the term GPC is used for those analyzing plastics or synthetic polymers (organic or water-soluble) using either organic or aqueous containing eluents. By comparison, SEC is more commonly used to describe size-based separations of biological compounds such as peptides and proteins.