Gel permeation chromatography ( GPC ) is a type of size-exclusion chromatography (SEC), that separates high molecular weight or colloidal analytes on the basis of size or diameter, 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. 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.
50-502: GPC may refer to: Science and medicine [ edit ] Gel permeation chromatography Generalized polynomial chaos Giant papillary conjunctivitis , a disease of the eye Gigaparsec (Gpc), a unit of distance Global Plant Clinic , an agricultural organization Glycophorin C , a sialoglycoprotein Glycerophosphorylcholine , or alpha-GPC Glypican ,
100-637: A college ice hockey arena on the campus of the Rochester Institute of Technology General Polygon Clipper , a graphics library Genuine Parts Company , an American service organization George Pearson Centre , a long-term care facility in Vancouver, Canada Georgia Perimeter College in Georgia, United States Global Privacy Control , a data protection signal for the web Global Product Classification Global Pound Conference ,
150-567: A conference series on international dispute resolution GNU Pascal , a computer program Goldwyn Pictures , an American film studio that eventually merged with other studios Government Procurement Card , a United Kingdom government purchasing card Government Purchase Card , a United States government purchasing program GPC Sport , an auto racing team Putnam County Airport , in Indiana, United States Remington GPC , an American assault rifle GPC (Mystery Science Theater 3000) ,
200-451: A constant flow free of fluctuations is especially important to the precision of the GPC analysis, as the flow-rate is used for the calibration of the molecular weight, or diameter. 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
250-448: A constant monomer and initiator concentration, such that the DP n is constant, the dispersity of the resulting monomer is between 1.5 and 2.0. As a result, reactor type does not affect dispersity for free radical polymerization reactions in any noticeable amount as long as conversion is low. For anionic polymerization, a form of living polymerization , the reactive anion intermediates have
300-470: A mixture. A collection of objects is called uniform if the objects have the same size, shape, or mass. A sample of objects that have an inconsistent size, shape and mass distribution is called non-uniform . The objects can be in any form of chemical dispersion , such as particles in a colloid , droplets in a cloud, crystals in a rock, or polymer macromolecules in a solution or a solid polymer mass. Polymers can be described by molecular mass distribution;
350-534: A more convenient method of determining the molecular weights of polymers. In fact most samples can be thoroughly analyzed in an hour or less. Other methods used in the past were fractional extraction and fractional precipitation. As these processes were quite labor-intensive molecular weights and mass distributions typically were not analyzed. Therefore, GPC has allowed for the quick and relatively easy estimation of molecular weights and distribution for polymer samples There are disadvantages to GPC, however. First, there
400-426: A population of particles can be described by size, surface area, and/or mass distribution; and thin films can be described by film thickness distribution. IUPAC has deprecated the use of the term polydispersity index , having replaced it with the term dispersity , represented by the symbol Đ (pronounced D-stroke ) which can refer to either molecular mass or degree of polymerization. It can be calculated using
450-585: A proteoglycan GPC Biotech , a German biopharmaceutical company Politics [ edit ] General People's Congress (disambiguation) Goa People's Congress , in India Green Party of Canada Group of Cameroonian Progressives Other uses [ edit ] Geiriadur Prifysgol Cymru , the University of Wales Dictionary of the Welsh language Gene Polisseni Center ,
500-481: A robot character from Mystery Science Theater 3000 Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title GPC . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=GPC&oldid=1216101453 " Category : Disambiguation pages Hidden categories: Short description
550-511: A special case of addition polymerization, leads to values very close to 1. Such is the case also in biological polymers, where the dispersity can be very close or equal to 1, indicating only one length of polymer is present. The reactor polymerization reactions take place in can also affect the dispersity of the resulting polymer. For bulk radical polymerization with low (<10%) conversion, anionic polymerization, and step growth polymerization to high conversion (>99%), typical dispersities are in
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#1732765754173600-469: A step-growth polymerization in a CSTR will allow some polymer chains out of the reactor before achieving high molecular weight, while others stay in the reactor for a long time and continue to react. The result is a much more broad molecular weight distribution, which leads to much larger dispersities. For a homogeneous CSTR, the dispersity is proportional to the square root of the Damköhler number , but for
650-500: A universal calibration curve which can be used for any polymer in that solvent. By determining the retention volumes (or times) of monodisperse polymer standards (e.g. solutions of monodispersed polystyrene in THF), a calibration curve can be obtained by plotting the logarithm of the molecular weight versus the retention time or volume. Once the calibration curve is obtained, the gel permeation chromatogram of any other polymer can be obtained in
700-417: Is a limited number of peaks that can be resolved within the short time scale of the GPC run. Also, as a technique GPC requires around at least a 10% difference in molecular weight for a reasonable resolution of peaks to occur. In regards to polymers, the molecular masses of most of the chains will be too close for the GPC separation to show anything more than broad peaks. Another disadvantage of GPC for polymers
750-450: Is a limited range of molecular weights that can be separated by each column, therefore the size of the pores for the packing should be chosen according to the range of molecular weight of analytes to be separated. For polymer separations the pore sizes should be on the order of the polymers being analyzed. If a sample has a broad molecular weight range it may be necessary to use several GPC columns with varying pores volumes in tandem to resolve
800-440: Is a measure of the distribution of molecular mass in a given polymer sample. Đ (PDI) of a polymer is calculated: where M w {\displaystyle M_{\mathrm {w} }} is the weight average molecular weight and M n {\displaystyle M_{\mathrm {n} }} is the number average molecular weight . M n {\displaystyle M_{\mathrm {n} }}
850-509: Is almost taken as unity. Typical dispersities vary based on the mechanism of polymerization and can be affected by a variety of reaction conditions. In synthetic polymers, it can vary greatly due to reactant ratio, how close the polymerization went to completion, etc. For typical addition polymerization , Đ can range around 5 to 20. For typical step polymerization, most probable values of Đ are around 2 — Carothers' equation limits Đ to values of 2 and below. Living polymerization ,
900-438: Is composed of molecules of the same mass. Nearly all natural polymers are uniform. Synthetic near-uniform polymer chains can be made by processes such as anionic polymerization, a method using an anionic catalyst to produce chains that are similar in length. This technique is also known as living polymerization . It is used commercially for the production of block copolymers . Uniform collections can be easily created through
950-420: Is concentration sensitive detectors which includes UV-VIS 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 (MALS). The resulting chromatogram is therefore a weight distribution of
1000-414: Is different from Wikidata All article disambiguation pages All disambiguation pages Gel permeation chromatography When characterizing polymers, it is important to consider their size distribution and dispersity ( Đ ) as well their molecular weight . Polymers can be characterized by a variety of definitions for molecular weight including the number average molecular weight (M n ),
1050-423: Is done using UV and RI detectors, although other combinations can be used. Gel permeation chromatography (GPC) has become the most widely used technique for analyzing polymer samples in order to determine their molecular weights and weight distributions. Examples of GPC chromatograms of polystyrene samples with their molecular weights and dispersities are shown on the left. Benoit and co-workers proposed that
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#17327657541731100-421: Is filled with a microporous packing material. The column is filled with the gel. Since the total penetration volume is the maximum volume permeated by the analytes, and there is no retention on the surface of the stationary phase, the total column volume is usually large, relatively to the sample volume. The eluent (mobile phase) should be the appropriate solvent to dissolve the polymer, should not interfere with
1150-450: Is more sensitive to molecules of low molecular mass, while M w {\displaystyle M_{\mathrm {w} }} is more sensitive to molecules of high molecular mass. The dispersity indicates the distribution of individual molecular masses in a batch of polymers . Đ has a value equal to or greater than 1, but as the polymer chains approach uniform chain length, Đ approaches unity (1). For some natural polymers Đ
1200-421: Is simply referred to as Đ . IUPAC has also deprecated the terms monodisperse , which is considered to be self-contradictory, and polydisperse , which is considered redundant, preferring the terms uniform and non-uniform instead. The terms monodisperse and polydisperse are however still preferentially used to describe particles in an aerosol . A uniform polymer (often referred to as a monodisperse polymer)
1250-400: Is that filtrations must be performed before using the instrument to prevent dust and other particulates from ruining the columns and interfering with the detectors. Although useful for protecting the instrument, there is the possibility of the pre-filtration of the sample removing higher molecular weight sample before it can be loaded on the column. Another possibility to overcome these issues is
1300-429: Is the case of humic acids and fulvic acids , natural polyelectrolyte substances having respectively higher and lower molecular weights. Another interpretation of dispersity is explained in the article Dynamic light scattering (cumulant method subheading). In this sense, the dispersity values are in the range from 0 to 1. The dispersity ( Đ ), also known as the polydispersity index ( PDI ) or heterogeneity index,
1350-452: The CSTR and end up with different concentrations of reactants. As a result, the dispersity of the reactor lies between that of a batch and that of a homogeneous CSTR. Step growth polymerization is most affected by reactor type. To achieve any high molecular weight polymer, the fractional conversion must exceed 0.99, and the dispersity of this reaction mechanism in a batch or PFR is 2.0. Running
1400-467: The GPC. Unfortunately, polystyrene tends to be a very linear polymer and therefore as a standard it is only useful to compare it to other polymers that are known to be linear and of relatively the same size. Gel permeation chromatography is conducted almost exclusively in chromatography systems. The experimental design is not much different from other techniques of High Performance liquid chromatography . Samples are dissolved in an appropriate solvent, in
1450-424: The ability to remain reactive for a very long time. In batch reactors or PFRs, well-controlled anionic polymerization can result in almost uniform polymer. When introduced into a CSTR however, the residence time distribution for reactants in the CSTR affects the dispersity of the anionic polymer due to the anion lifetime. For a homogeneous CSTR, the residence time distribution is the most probable distribution . Since
1500-435: The anionic polymerization dispersity for a batch reactor or PFR is basically uniform, the molecular weight distribution takes on the distribution of the CSTR residence times, resulting in a dispersity of 2. Heterogeneous CSTRs are similar to homogeneous CSTRs, but the mixing within the reactor is not as good as in a homogeneous CSTR. As a result, there are small sections within the reactor that act as smaller batch reactors within
1550-415: The case of GPC these tend to be organic solvents and after filtering the solution it is injected onto a column. The separation of multi-component mixture takes place in the column. The constant supply of fresh eluent to the column is accomplished by the use of a pump. Since most analytes are not visible to the naked eye a detector is needed. Often multiple detectors are used to gain additional information about
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1600-410: The column, hence they elute sooner. Each type of column has a range of molecular weights that can be separated, according to their pores sizes. If an analyte is too large relative to the column's pores, it will not be retained at all and will be totally excluded; conversely, if the analyte is small relative to the pores sizes, it will be totally permeating. Analytes that are totally excluded, elute with
1650-418: The dispersity is often controlled by the proportion of chains that terminate via combination or disproportionation. The rate of reaction for free radical polymerization is exceedingly quick, due to the reactivity of the radical intermediates. When these radicals react in any reactor, their lifetimes, and as a result, the time needed for reaction are much shorter than any reactor residence time. For FRPs that have
1700-417: The equation Đ M = M w / M n , where M w is the weight-average molar mass and M n is the number-average molar mass. It can also be calculated according to degree of polymerization, where Đ X = X w / X n , where X w is the weight-average degree of polymerization and X n is the number-average degree of polymerization. In certain limiting cases where Đ M = Đ X , it
1750-485: The fact that there is a final elution volume for all unretained analytes. Additionally, GPC can provide narrow bands, although this aspect of GPC is more difficult for polymer samples that have broad ranges of molecular weights present. Finally, since the analytes do not interact chemically or physically with the column, there is a lower chance for analyte loss to occur. For investigating the properties of polymer samples in particular, GPC can be very advantageous. GPC provides
1800-535: The free volume outside around the particles (V o ), the total exclusion limit, while analytes that are completely delayed, elute with the solvent, marking the total permeation volume of the column, including also the solvent held inside the pores (V i ). The total volume can be considered by the following equation, where V g is the volume of the polymer gel and V t is the total volume: V t = V g + V i + V o {\displaystyle Vt=Vg+Vi+Vo} As can be inferred, there
1850-523: The hydrodynamic volume, V η , which is proportional to the product of [η] and M, where [η] is the intrinsic viscosity of the polymer in the SEC eluent, may be used as the universal calibration parameter. If the Mark–Houwink–Sakurada constants K and α are known (see Mark–Houwink equation ), a plot of log [η]M versus elution volume (or elution time) for a particular solvent, column and instrument provides
1900-409: The mobile and stationary phases to separate analytes. Separation occurs via the use of porous gel beads packed inside a column (see stationary phase (chemistry) ). The principle of separation relies on the differential exclusion or inclusion of the macromolecules by the porous gel stationary phase. Larger molecules are excluded from entering the pores and elute earlier, while smaller molecules can enter
1950-431: 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
2000-749: The polymer sample. The availability of a detector makes the fractionation convenient and accurate. Gels are used as stationary phase for GPC. The pore size of a gel must be carefully controlled in order to be able to apply the gel to a given separation. Other desirable properties of the gel forming agent are the absence of ionizing groups and, in a given solvent, low affinity for the substances to be separated. Commercial gels like PLgel & Styragel (cross-linked polystyrene-divinylbenzene), LH-20 (hydroxypropylated Sephadex ), Bio-Gel ( cross-linked polyacrylamide ), HW-20 & HW-40 (hydroxylated methacrylic polymer ), and agarose gel are often used based on different separation requirements. The column used for GPC
2050-406: The pores, thus staying longer inside the column. The entire process takes place without any interaction of the analytes with the surface of the stationary phase. The smaller analytes relative to the pore sizes can permeate these pores and spend more time inside the gel particles, increasing their retention time. Conversely, larger analytes relative to the pores sizes spend little if any time inside
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2100-588: The response of the polymer analyzed, and should wet the packing surface and make it inert to interactions with the polymers. The most common eluents for polymers that dissolve at room temperature GPC are tetrahydrofuran (THF), o -dichlorobenzene and trichlorobenzene at 130–150 °C for crystalline polyalkynes and hexafluoroisopropanol (HFIP) for crystalline condensation polymers such as polyamides and polyesters . There are two types of pumps available for uniform delivery of relatively small liquid volumes for GPC: piston or peristaltic pumps. The delivery of
2150-417: The same size but different chemical compositions is possible. Dispersity Đ M = M w / M n where M w is the mass-average molar mass (or molecular weight) and M n is the number-average molar mass (or molecular weight). Pure Appl. Chem. , 2009 , 81(2), 351-353 In chemistry , the dispersity is a measure of the heterogeneity of sizes of molecules or particles in
2200-407: The same solvent and the molecular weights (usually M n and M w ) and the complete molecular weight distribution for the polymer can be determined. A typical calibration curve is shown to the right and the molecular weight from an unknown sample can be obtained from the calibration curve. As a separation technique, GPC has many advantages. First of all, it has a well-defined separation time due to
2250-470: The sample fully. GPC is often used to determine the relative molecular weight of polymer samples as well as the distribution of molecular weights. What GPC truly measures is the molecular volume and shape function as defined by the intrinsic viscosity . If comparable standards are used, this relative data can be used to determine molecular weights within ± 5% accuracy. Polystyrene standards with dispersities of less than 1.2 are typically used to calibrate
2300-517: The separation by field-flow fractionation (FFF). Field-flow fractionation (FFF) can be considered as an alternative to GPC, especially when particles or high molar mass polymers cause clogging of the column, shear degradation is an issue or agglomeration takes place but cannot be made visible. FFF is separation in an open flow channel without having a static phase involved so no interactions occur. With one field-flow fractionation version, thermal field-flow fractionation , separation of polymers having
2350-430: The table below. With respect to batch and plug flow reactors (PFRs), the dispersities for the different polymerization methods are the same. This is largely because while batch reactors depend entirely on time of reaction, plug flow reactors depend on distance traveled in the reactor and its length. Since time and distance are related by velocity, plug flow reactors can be designed to mirror batch reactors by controlling
2400-429: The use of template-based synthesis, a common method of synthesis in nanotechnology . A polymer material is denoted by the term disperse, or non-uniform, if its chain lengths vary over a wide range of molecular masses. This is characteristic of man-made polymers. Natural organic matter produced by the decomposition of plants and wood debris in soils ( humic substances ) also has a pronounced polydispersed character. It
2450-438: The velocity and length of the reactor. Continuously stirred-tank reactors (CSTRs) however have a residence time distribution and cannot mirror batch or plug flow reactors, which can cause a difference in the dispersity of final polymer. The effects of reactor type on dispersity depend largely on the relative timescales associated with the reactor, and with the polymerization type. In conventional bulk free radical polymerization,
2500-550: The weight average molecular weight (M w ) (see molar mass distribution ), the size average molecular weight (M z ), or the viscosity molecular weight (M v ). GPC allows for the determination of Đ as well as M v and, based on other data, the M n , M w , and M z can be determined. GPC is a type of chromatography in which analytes are separated, based on their size or hydrodynamic volume ( radius of gyration ). This differs from other chromatographic techniques, which depend upon chemical or physical interactions between
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