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In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent called the mobile phase, which carries it through a system on which a material called the stationary phase is fixed. Because the different constituents of the mixture tend to have different affinities for the stationary phase and are retained for different lengths of time depending on their interactions with its surface sites, the constituents travel at different apparent velocities in the mobile fluid, causing them to separate. The separation is based on the differential partitioning between the mobile and the stationary phases. Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase and thus affect the separation.
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify specific components in mixtures. The mixtures can originate from food, chemicals, pharmaceuticals, biological, environmental and agriculture, etc, which have been dissolved into liquid solutions.
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.
Electron ionization is an ionization method in which energetic electrons interact with solid or gas phase atoms or molecules to produce ions. EI was one of the first ionization techniques developed for mass spectrometry. However, this method is still a popular ionization technique. This technique is considered a hard ionization method, since it uses highly energetic electrons to produce ions. This leads to extensive fragmentation, which can be helpful for structure determination of unknown compounds. EI is the most useful for organic compounds which have a molecular weight below 600. Also, several other thermally stable and volatile compounds in solid, liquid and gas states can be detected with the use of this technique when coupled with various separation methods.
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.
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture. In preparative chromatography, GC can be used to prepare pure compounds from a mixture.
Richard Laurence Millington Synge FRS FRSE FRIC FRSC MRIA was a British biochemist, and shared the 1952 Nobel Prize in Chemistry for the invention of partition chromatography with Archer Martin.
Analytical technique is a method used to determine a chemical or physical property of a chemical substance, chemical element, or mixture. There is a wide variety of techniques used for analysis, from simple weighing to advanced techniques using highly specialized instrumentation.
Molecular imprinting is a technique to create template-shaped cavities in polymer matrices with predetermined selectivity and high affinity. This technique is based on the system used by enzymes for substrate recognition, which is called the "lock and key" model. The active binding site of an enzyme has a shape specific to a substrate. Substrates with a complementary shape to the binding site selectively bind to the enzyme; alternative shapes that do not fit the binding site are not recognized.
Liquid chromatography–mass spectrometry (LC–MS) is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry (MS). Coupled chromatography – MS systems are popular in chemical analysis because the individual capabilities of each technique are enhanced synergistically. While liquid chromatography separates mixtures with multiple components, mass spectrometry provides spectral information that may help to identify each separated component. MS is not only sensitive, but provides selective detection, relieving the need for complete chromatographic separation. LC–MS is also appropriate for metabolomics because of its good coverage of a wide range of chemicals. This tandem technique can be used to analyze biochemical, organic, and inorganic compounds commonly found in complex samples of environmental and biological origin. Therefore, LC–MS may be applied in a wide range of sectors including biotechnology, environment monitoring, food processing, and pharmaceutical, agrochemical, and cosmetic industries. Since the early 2000s, LC–MS has also begun to be used in clinical applications.
Field-flow fractionation, abbreviated FFF, is a separation technique invented by J. Calvin Giddings. The technique is based on separation of colloidal or high molecular weight substances in liquid solutions, flowing through the separation platform, which does not have a stationary phase. It is similar to liquid chromatography, as it works on dilute solutions or suspensions of the solute, carried by a flowing eluent. Separation is achieved by applying a field or cross-flow, perpendicular to the direction of transport of the sample, which is pumped through a long and narrow laminar channel. The field exerts a force on the sample components, concentrating them towards one of the channel walls, which is called accumulation wall. The force interacts with a property of the sample, thereby the separation occurs, in other words, the components show differing "mobilities" under the force exerted by the crossing field. As an example, for the hydraulic, or cross-flow FFF method, the property driving separation is the translational diffusion coefficient or the hydrodynamic size. For a thermal field, it is the ratio of the thermal and the translational diffusion coefficient.
Two-dimensional chromatography is a type of chromatographic technique in which the injected sample is separated by passing through two different separation stages. Two different chromatographic columns are connected in sequence, and the effluent from the first system is transferred onto the second column. Typically the second column has a different separation mechanism, so that bands that are poorly resolved from the first column may be completely separated in the second column. Alternately, the two columns might run at different temperatures. During the second stage of separation the rate at which the separation occurs must be faster than the first stage, since there is still only a single detector. The plane surface is amenable to sequential development in two directions using two different solvents.
Capillary electrophoresis–mass spectrometry (CE–MS) is an analytical chemistry technique formed by the combination of the liquid separation process of capillary electrophoresis with mass spectrometry. CE–MS combines advantages of both CE and MS to provide high separation efficiency and molecular mass information in a single analysis. It has high resolving power and sensitivity, requires minimal volume and can analyze at high speed. Ions are typically formed by electrospray ionization, but they can also be formed by matrix-assisted laser desorption/ionization or other ionization techniques. It has applications in basic research in proteomics and quantitative analysis of biomolecules as well as in clinical medicine. Since its introduction in 1987, new developments and applications have made CE-MS a powerful separation and identification technique. Use of CE–MS has increased for protein and peptides analysis and other biomolecules. However, the development of online CE–MS is not without challenges. Understanding of CE, the interface setup, ionization technique and mass detection system is important to tackle problems while coupling capillary electrophoresis to mass spectrometry.
Milton L. Lee is the H. Tracy Hall Professor of Chemistry at Brigham Young University (BYU).
Leslie Stephen Ettre was a Hungarian-American analytical chemist and scientist who was known for his contributions to the field of chromatography, in particular open-tubular gas chromatography, as well as to documentation of the history of chromatography.
The Charged Aerosol Detector (CAD) is a detector used in conjunction with high-performance liquid chromatography (HPLC) and ultra high-performance liquid chromatography (UHPLC) to measure the amount of chemicals in a sample by creating charged aerosol particles which are detected using an electrometer. It is commonly used for the analysis of compounds that cannot be detected using traditional UV/Vis approaches due to their lack of a chromophore. The CAD can measure all non-volatile and many semi-volatile analytes including, but not limited to, antibiotics, excipients, ions, lipids, natural products, biofuels, sugars and surfactants. The CAD, like other aerosol detectors, falls under the category of destructive general-purpose detectors.
Daniel Wayne Armstrong is an American chemist who specializes in separation science, chiral molecular recognition, bioanalytic analysis, mass spectrometry and colloid chemistry. He is the Robert A. Welch Distinguished Professor at the University of Texas at Arlington. He has authored ~ 750 publications including 35 book chapters, a book, and holds over 35 patents on separation technologies. He was an associate editor for the prestigious American Chemical Society journal Analytical Chemistry. He is a fellow of the American Chemical Society, Royal Chemical Society (UK), and the National Academy of Inventors. Armstrong has given over 560 invited seminars worldwide at international conferences, universities and corporations. His research and patents formed the basis for two companies: Advanced Separation Technologies, Inc; which was acquires by Sigma-Aldrich Corporation in 2006 and AZYP, LLC in Arlington, TX. His published work has been cited over 50,000 times and his h-index is 115. He is believed to have mentored more graduate level analytical chemists than any living scientist.
Milos Vratislav Novotny is an American chemist, currently the Distinguished Professor Emeritus and Director of the Novotny Glycoscience Laboratory and the Institute for Pheromone Research at Indiana University, and also a published author. Milos Novotny received his Bachelor of Science from the University of Brno, Czechoslovakia in 1962. In 1965, Novotny received his Ph.D. at the University of Brno. Novotny also holds honorary doctorates from Uppsala University, Masaryk University and Charles University, and he has been a major figure in analytical separation methods. Novotny was recognized for the development of PAGE Polyacrylamide Gel-filled Capillaries for Capillary Electrophoresis in 1993. In his years of work dedicated to analytical chemistry he has earned a reputation for being especially innovative in the field and has contributed a great deal to several analytical separation methods. Most notably, Milos has worked a great deal with microcolumn separation techniques of liquid chromatography, supercritical fluid chromatography, and capillary electrophoresis. Additionally, he is highly acclaimed for his research in proteomics and glycoanalysis and for identifying the first mammalian pheromones.
Janusz Boleslaw Pawliszyn is a Polish chemist. He is a Canada Research Chair at the University of Waterloo and Natural Sciences and Engineering Research Council of Canada Industrial Research Chair in New Analytical Methods and Technologies.
Susan M. Lunte is an American chemist who is the Ralph N. Adams Distinguished Professor of Chemistry and Pharmaceutical Chemistry at the University of Kansas. She also works as director of the NIH COBRE Center for Molecular Analysis of Disease Pathways. She was awarded the 2023 ACS Award in Analytical Chemistry.
References
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- 1 2 3 4 5 "September meeting" (PDF). Society for Analytical Chemists of Pittsburgh. September 9, 2015. Retrieved 14 July 2016.
- 1 2 3 4 Cashin-Garbutt, April (January 14, 2016). "Determining ectopeptidase activity: an interview with Professor Stephen Weber, University of Pittsburgh". News Medical. Retrieved 14 July 2016.
- 1 2 3 4 Tsarevsky, Nick (2008). "Dr. Stephen G. Weber Named Recipient of the 2008 Pittsburgh Award" (PDF). The Crucible. XCIV (1): 1. Retrieved 14 July 2016.
- ↑ Weber, Stephen G. (1986). "Chapter 7: Detection based on electrical and electrochemical measurements" . In Yeung, Edward S. (ed.). Detectors for liquid chromatography. New York: Wiley. pp. 229–291. ISBN 9780471821694.
- 1 2 "Steve Weber". University of Pittsburgh. Retrieved 15 July 2016.
- ↑ Ou, Yangguang; Wu, Juanfang; Sandberg, Mats; Weber, Stephen G. (29 August 2014). "Electroosmotic perfusion of tissue: sampling the extracellular space and quantitative assessment of membrane-bound enzyme activity in organotypic hippocampal slice cultures". Analytical and Bioanalytical Chemistry. 406 (26): 6455–6468. doi:10.1007/s00216-014-8067-2. PMC 4184924 . PMID 25168111.
- ↑ "Palmer Award". Minnesota Chromatography Forum. Retrieved 14 July 2016.
- ↑ "Provost's Award for Excellence in Mentoring". University of Pittsburgh. Retrieved 14 July 2016.