Gel Permeation Chromatography (GPC), also known as Size Exclusion Chromatography (SEC), is a liquid chromatography technique used to separate molecules based on their size. Unlike other chromatographic methods that rely on chemical interactions, GPC/SEC separates compounds physically: larger molecules pass quickly through the column because they cannot enter the pores of the stationary phase, while smaller molecules penetrate the pores and take longer to elute. This makes the technique particularly useful for determining molecular weight distribution and studying the structure of polymers, proteins, and other macromolecules. GPC/SEC is widely applied in polymer research, biopharmaceutical development, protein analysis, and quality control testing, providing valuable insights into molecular size, shape, and purity.