page_title: Gel permeation chromatography
section_title: Detector
hierarchical_section_title: Gel permeation chromatography / Material and methods / Detector
caption_attribution_description: English: A generic example of what a GPC separation would look like
context_page_description: Gel permeation chromatography is a type of size exclusion chromatography, that separates analytes on the basis of size, typically in organic solvents. The technique is often used for the analysis of polymers. As a technique, SEC was first developed in 1955 by Lathe and Ruthven. The term gel permeation chromatography can be traced back to J.C. Moore of the Dow Chemical Company who investigated the technique in 1964 and the proprietary column technology was licensed to Waters Corporation, who subsequently commercialized this technology in 1964. GPC systems and consumables are now also available from a number of manufacturers. It is often necessary to separate polymers, both to analyze them as well as to purify the desired product.
  When characterizing polymers, it is important to consider the dispersity as well the molecular weight. Polymers can be characterized by a variety of definitions for molecular weight including the number average molecular weight, the weight average molecular weight, the size average molecular weight, or the viscosity molecular weight. GPC allows for the determination of Đ as well as Mᵥ and based on other data, the Mₙ, Mw, and Mz can be determined.
context_section_description: In GPC, the concentration by weight of polymer in the eluting solvent may be monitored continuously with a detector.  There are many detector types available and they can be divided into two main categories.  The first is concentration sensitive detectors which includes UV absorption, differential refractometer (DRI) or refractive index (RI) detectors, infrared (IR) absorption and density detectors.  The second category is molecular weight sensitive detectors, which include low angle light scattering detectors (LALLS) and multi angle light scattering (MALLS).  The resulting chromatogram is therefore a weight distribution of the polymer as a function of retention volume. 
  The most sensitive detector is the differential UV photometer and the most common detector is the differential refractometer (DRI). When characterizing copolymer, it is necessary to have two detectors in series.  For accurate determinations of copolymer composition at least two of those detectors should be concentration detectors.  The determination of most copolymer compositions is done using UV and RI detectors, although other combinations can be used.
caption: GPC Chromatogram; Vo= no retention, Vt= complete retention, A and B = partial retention
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