Gel permeation chromatography GPC and size exclusion chromatography SEC are essentially the same technique, with the primary difference being the type of sample being analyzed. GPC is typically used for the analysis of synthetic polymers, while SEC is used for the analysis of biological macromolecules such as proteins and nucleic acids. Both techniques are based on the separation of molecules according to their size hydrodynamic volume in solution.The main principle behind GPC/SEC is that smaller molecules can penetrate the pores of the stationary phase usually a porous gel more easily than larger molecules. As a result, larger molecules elute from the column earlier than smaller ones. This allows for the separation of molecules based on their size, which is often correlated with their molecular weight.GPC/SEC can be used to characterize polymers with different molecular weights and distributions by providing information on the following parameters:1. Molecular weight MW : The average molecular weight of a polymer sample can be determined by comparing its elution time with those of known standards. This is typically done using a calibration curve, which plots the elution time against the molecular weight of the standards.2. Molecular weight distribution MWD : The width of the elution peak in a GPC/SEC chromatogram provides information on the molecular weight distribution of the sample. A narrow peak indicates a narrow MWD i.e., the polymer chains have similar molecular weights , while a broad peak indicates a wide MWD i.e., the polymer chains have a range of molecular weights .3. Polydispersity index PDI : The PDI is a measure of the heterogeneity of a polymer sample and is calculated as the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn . A PDI of 1 indicates a monodisperse sample i.e., all polymer chains have the same molecular weight , while a PDI greater than 1 indicates a polydisperse sample i.e., the polymer chains have a range of molecular weights .By analyzing these parameters, GPC/SEC can provide valuable information on the molecular weight and distribution of a polymer sample, which can be used to assess its physical properties, performance, and suitability for various applications.