The short version of mobile phase fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-17. Anything still debated is marked as such rather than presented as settled.
Separation performance depends on particle size, pore size, column length, and the chemistry of the stationary phase. Smaller particles generally improve efficiency but require higher pressure and suitable instrumentation. The mobile phase often contains buffers and organic solvents that influence retention and selectivity. Testing labs select conditions based on the analytes, sample matrix, and required sensitivity. Method development frequently involves screening several columns and solvent mixtures before a final set of conditions is chosen.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample by passing them through a packed column under pressure. A pump delivers a mobile phase at a controlled flow rate, and an injector introduces the sample into the stream. Differences in how analytes partition between the mobile phase and the stationary phase cause them to exit the column at different times. Detection then records a signal proportional to the amount of each separated substance. The resulting chromatogram provides retention times and peak areas for identification and quantification.
Instrumentation includes a solvent delivery system, an autosampler, a column oven, and one or more detectors. Reversed-phase columns with chemically modified silica are widely used, but normal-phase, ion-exchange, size-exclusion, and affinity modes exist for specific separations. Detectors may rely on ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry. Column temperature, mobile phase composition, and flow rate are adjusted to improve resolution. System pressure is monitored because rising pressure can indicate column blockage or deteriorating packing.
Separation modes differ by the chemistry of the stationary phase and the composition of the mobile phase. Reversed-phase testing uses a nonpolar column and polar solvents, making it common for pharmaceutical, environmental, and food analytes. Normal-phase testing uses a polar column and nonpolar solvents for compounds that are poorly retained in reversed-phase systems. Ion-exchange and ion-pair methods separate charged species, while size-exclusion methods sort molecules by hydrodynamic volume. Gradient elution changes solvent strength over time to resolve complex mixtures, and isocratic elution holds solvent composition constant for simpler assays.
Key performance measures include retention time, peak area, peak height, resolution, tailing factor, and plate count. Retention time helps identify a peak under fixed conditions, but confirmation often requires a second method or detector. Peak area and height relate to concentration through calibration curves, which may be linear or nonlinear depending on the detector response. Resolution describes separation between adjacent peaks, while tailing factor and plate count describe peak shape and column efficiency. Performance checks verify these values before and during a run to confirm that the instrument is performing within limits.
| Property | Value | Notes |
|---|---|---|
| Separation principle | Differential partitioning | Analytes distribute between mobile and stationary phases. |
| Mobile phase | Liquid solvent mixture | Composition controls retention and selectivity. |
| Stationary phase | Packed column particles | Often chemically bonded silica. |
| Typical detector | UV-Vis or photodiode array | Mass spectrometry is also common. |
| Common synonym | High-performance liquid chromatography | Abbreviated as HPLC. |
Method validation establishes that an HPLC procedure is suitable for its intended use. Key parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Accuracy measures agreement with a true or accepted value, while precision describes repeatability and intermediate precision. Specificity confirms that the method measures the analyte without interference from impurities, degradants, or excipients. Validation is documented in a protocol and report, and acceptance criteria are set before experiments begin. Regulatory guidance varies by region, but the general principles are widely harmonized.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Common checks include retention time, peak area, resolution between critical pairs, tailing factor, and theoretical plate count. Results are compared with predefined limits, and a failed check requires investigation before sample results are reported. Quality control samples at low, middle, and high concentrations are injected at intervals to monitor accuracy and precision. Blank injections detect carryover and contamination, while control charts track performance over time.
Validation demonstrates that a method is suitable for its intended use. Typical performance characteristics include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Regulators and standards organizations provide frameworks, but specific requirements depend on the application and jurisdiction. System suitability tests are run before sample analysis to confirm resolution, peak symmetry, retention time repeatability, and sensitivity. A validated method is not permanently fixed; changes may require partial or full revalidation.
Routine HPLC testing depends on controlled reagents, calibrated instruments, and documented procedures. Columns degrade over time, so retention times and peak shapes are monitored for drift. Mobile phases are filtered and degassed to prevent pump damage and detector noise. Reference standards must be traceable and stored under suitable conditions. Data handling systems record injections, calculations, and audit trails. Quality control samples interspersed with unknowns help detect errors during a run.
Developing an HPLC method begins with defining the purpose, such as quantifying a main component, measuring impurities, or confirming identity. Analysts select separation mode, column, mobile phase, detection, and sample preparation based on analyte properties and matrix. Experiments vary solvent strength, pH, buffer type, and temperature to achieve resolution between critical peaks. The goal is a robust method that produces reliable results across instruments and operators. Method development often involves trial runs and statistical optimization.
=== Supercritical fluid in power generation === The efficiency of a heat engine is ultimately dependent on the temperature difference between heat source and sink (Carnot cycle). To improve efficiency of power stations the operating temperature must be raised. Using water as the working fluid, this takes it into supercritical conditions. Efficiencies can be raised from about 39% for subcritical operation to about 45% using current technology. Many coal-fired supercritical steam generators are operational all over the world. Supercritical carbon dioxide is also proposed as a working fluid, which would have the advantage of lower critical pressure than water, but issues with corrosion are not yet fully solved. One proposed application is the Allam cycle. Supercritical water reactors (SCWRs) are proposed advanced nuclear systems that offer similar thermal efficiency gains.
Light sources such as fluorescent lamps, high-intensity discharge lamps and LED lamps have higher luminous efficiency. These devices produce light by luminescence. Their light has bands of characteristic wavelengths, without the "tail" of invisible infrared emissions, instead of the continuous spectrum produced by a thermal source. By careful selection of fluorescent phosphor coatings or filters which modify the spectral distribution, the spectrum emitted can be tuned to mimic the appearance of incandescent sources, or other different color temperatures of white light. When used for tasks sensitive to color, such as motion picture lighting, these sources may require particular techniques to duplicate the appearance of incandescent lighting. Metamerism describes the effect of different light spectrum distributions on the perception of color.
HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq) Neutralization is the basis of titration, where a pH indicator shows equivalence point when the equivalent number of moles of a base have been added to an acid. It is often wrongly assumed that neutralization should result in a solution with pH 7.0, which is only the case with similar acid and base strengths during a reaction. Neutralization with a base weaker than the acid results in a weakly acidic salt. An example is the weakly acidic ammonium chloride, which is produced from the strong acid hydrogen chloride and the weak base ammonia. Conversely, neutralizing a weak acid with a strong base gives a weakly basic salt (e.g., sodium fluoride from hydrogen fluoride and sodium hydroxide).
=== Impact of Coronavirus and CARES Act of 2020 === The COVID-19 pandemic in the United States impacted the economy significantly beginning in March 2020, as businesses were shut-down and furloughed or fired personnel. About 16 million persons filed for unemployment insurance in the three weeks ending April 9. It caused the number of unemployed persons to increase significantly, which is expected to reduce tax revenues while increasing automatic stabilizer spending for unemployment insurance and nutritional support. As a result of the adverse economic impact, both state and federal budget deficits will dramatically increase, even before considering any new legislation. To help address lost income for millions of workers and assist businesses, Congress and President Trump enacted the Coronavirus Aid, Relief, and Economic Security Act (CARES) on March 18, 2020. It included loans and grants for businesses, along with direct payments to individuals and additional funding for unemployment insurance. Some or all of the loans may ultimately be paid back including interest, while the spending measures should dampen the negative budgetary impact of the economic disruption. While the law will almost certainly increase budget deficits relative to the January 2020 10-year CBO baseline (completed prior to the Coronavirus), in the absence of the legislation, a complete economic collapse could have occurred. CBO provided a preliminary score for the CARES Act on April 16, 2020, estimating that it would increase federal deficits by about $1.8 trillion over the 2020-2030 period.
Sources: en.wikipedia.org
From this revolution, the 1950s also saw the advent of paper chromatography, reversed-phase partition chromatography (RPC), and hydrophobic interaction chromatography (HIC). The first gels for use in LC were created using cross-linked dextrans (Sephadex) in an attempt to realize Synge's prediction that a unique single-piece stationary phase could provide an ideal chromatographic solution. In the 1960s, polyacrylamide and agarose gels were created in a further attempt to create a single-piece stationary phase, but the purity of and stability of available components did not prove useful for implementation in the HPLC. In this decade, affinity chromatography was invented, an ultra-violet (UV) detector was used for the first time in conjunction with LC, and, most importantly, the modern HPLC was born. Csaba Horvath led the development of modern HPLC by piecing together laboratory equipment to suit his purposes. In 1968, Picker Nuclear Company marketed the first commercially available HPLC as a “Nucleic Acid Analyzer.” The following year, the first international symposia on HPLC was held, and Kirkland at DuPont was able to functionalize controlled porosity pellicular particles for the first time. The 1970s and 1980s witnessed a renewed interest in separations media with reduced interparticular void volumes. Perfusion chromatography showed, for the first time, that chromatography media could support high flow rates without sacrificing resolution. Monoliths aptly fit into this new class of media, as they exhibit no void volume and can withstand flow rates up to 9mL/minute.
Warden III, who largely planned the USAF attacks; within ten minutes of the attacks by 21 F117 aircraft on 38 targets, Iraq had lost its communications and radar; Lt-Col David Deptula; in the first wave were 4 Saudi Arabian Tornado aircraft, 4 Grumman A-6 Intruder and SEAD McDonnell Douglas F-4G Wild Weasel V aircraft, 5 Northrop Grumman EA-6B Prowler aircraft to provide electronic jamming of the Iraq airspace, and 21 McDonnell Douglas F/A-18 Hornet aircraft, each which dropped the AGM-88 HARM anti-radiation missile, to destroy the Iraq surface to air missile capability; Tomahawk missiles were fired from battleships in the Gulf and submarines in the Red Sea; the General Dynamics F-111 had around four thousand gallons of fuel; before advanced guidance systems for munitions, munitions would land according to the circular error probability, which was around a half-mile for a B-17 in World War II; the first laser-guided munitions were the Pave Tack system, which debuted on the F-111 in 1982, first deployed by F-111 aircraft from RAF Lakenheath; Duncan Lennox, editor of Jane's Strategic Weapon Systems; Theodore Postol; on one evening, twenty-eight MIM-104 Patriot missiles were launched against five ballistic missiles, which had broken up on re-entry to the earth's atmosphere - hitting any of these fractured ballistic missiles was almost impossible, due to the unforeseen changing aerodynamics; Lt-Col George Cusimano, deputy director of the USAF joint; the joint also deployed synthetic-aperture radar, to give a fuller view of ground forces, from the AN/APG-76 Doppler radar; the ground picture could be relayed to ground forces, such as in the Battle of Khafji on 29 January 1991; Royal Scots 1st Battalion, with GKN Warrior tracked armoured vehicles and Major John Potter; the experimental Ferranti TIALD laser-guided munitions were deployed by RAF Panavia Tornado aircraft to destroy Iraq hardened aircraft shelters in February 1991; 39th Regiment Royal Artillery deployed the M270 Multiple Launch Rocket System (MLRS); the land battle began on 24 February 1991, watched by the DOAE in Surrey; the land war did not last long, and on 26 February 1991 retreating Iraqi vehicles and tanks were systematically destroyed by AGM-114 Hellfire missiles, launched from undetected Boeing AH-64 Apache helicopters, resulting in total destruction; the USS Wisconsin battleship fired at Failaka Island, with surveillance provided by its AAI RQ-2 Pioneer drone. Narrated by Edward Hardwicke, directed by Chris Haws, produced by Richard Melman, made by InCA Productions 18 August The Healing Mind, about the field of psychoneuroimmunology; psychiatrist Janice Kielcolt-Glaser of Ohio State University College of Medicine; psychologist Barrie R. Cassileth; chemical pathologist Malcolm Carruthers takes a blood sample from a candidate, who has been driven around Brands Hatch at 115 mph; Theodore Melnechuk of the University of California; the body's immune system - the phagocytes destroy foreign bacteria, the natural killer cells destroy the body's own cells that are too damaged, and the lymphocyte T cells and B cells remember pathogens, with a corresponding antibody; experimental psychologist Robert Ader of the University of Rochester Medical Center conducted research on rats in 1975, with cyclophosphamide, which weakens the immune system, and immunologist Nicholas Cohen; prolonged secretion of endogenous opioid peptides may lower the immune function; neuroscientist David L. Felten of the University of Rochester; psychoimmunologist Nick Hall of the University of South Florida College of Medicine and an experiment with drama students, where lowering of T cells was found; Kathleen Dillon of Western New England College, where an experiment measured Ig A of candidates who watched types of television content, and found that Ig A temporarily increased with amusing content; psychiatrist Fawzy Fawzy of the University of California; psychiatrist Margaret Kemeny of UCLA. Narrated by Geoff Watts (of Radio 4's former Science Now series, produced by Geoff Deehan in the 1970s), directed by Yavar Abbas, produced by Geoff Deehan, made by Sandlin Productions 25 August Spacesuit, the spacesuits that astronauts wore during the Apollo missions to the Moon, and whether such spacesuits would be advanced enough to be worn for future missions to Mars; by 2020, NASA expected to have landed on Mars; at sea-level, air pressure is 14 PSI; ILC Dover in Newark, Delaware has made all NASA spacesuits since the late 1960s; medical research at the Ames Research Center; Joe Kosmo, head of NASA spacesuit design; the invention of the defecation-mitten by Matthew Radnofsky; Bruce Webbon of the Ames Research Centre; the Johnson Space Center also worked on suit design. Directed by Patrick Uden, made by Uden Associates 1 September The Falls, about the Niagara Falls. Produced by Clare Odgers, made by the National Film Board of Canada and Primitive Features 8 September Re-inventing Japan, looking at Japan's success in applied science, contrasted with less success in pure science and whether Japan could enhance its pure science industry enough, which has connections with a country's own cultural values and outlook, and how Britain has excelled in pure science, but how much that university funding cuts could erode Britain's prowess in pure science; Japan few Nobel prizes, but excelled at applied science and exploiting others' research by reverse engineering; Canon had £6bn of sales, of which 40% were photocopiers, such as the L5; Hajime Mitarai, research director of Canon, and how Canon had eight product divisions, with their own engineering staff in each division, with process physicists and inorganic chemists; with Western science innovations, it often came from a set of individuals, whereas Japan's innovation culture revolved around much intense group cooperation, not individuals; Japan had only won five Nobel prizes since the 1950s - the US had won 135; a youthful Matt Ridley of The Economist; Fujitsu was the world's second-largest manufacturer of computers, and had bought ICL (which had been Ferranti) in 1990, and sold £10bn a year; Naoki Yokoyama and Takahiko Misugi of Fujitsu; Japan could not rely on other countries research anymore, and had to conduct more in-house research; Japan's culture was not greatly known for originality or taking risks, or being surprised; pathologist Sir Anthony Epstein and how Japan greatly revered tradition, and conformity, possibly viewing anyone who didn't likewise confirm as troublesome; electrical engineer Hiroya Fujisaki, of Tokyo University and known for the Fujisaki model, and that he thought that Japan's culture had historically eroded originality; the national research organisation Riken was formed in 1917, and made great progress, with a large cyclotron, and visited by Einstein in December 1922, but the US was suspicious after the war, and destroyed Riken's cyclotron; Minoru Oda, head of Riken from 1988 to 1993; the US distrusted Japan, and preferred Japan to work on mainly applied science; physicist Akira Tonomura at the Hitachi Advanced Laboratory, which had the world's largest electron microscope; Shojiro Asai of Hitachi; the Canon Advanced Research Laboratory; the Tsukuba Science City and the University of Tsukuba, built by the Japanese government for £6bn, and home of the Japanese ERATO science innovation agency; Genya Chiba, director of ERATO; Michio Nagai, former minister of education in the mid-1970s. Directed by Bob Bee, produced by Michael Wills (later Labour MP from 1997 to 2010 for North Swindon), and made by Juniper Productions 13 September Theme Park Heaven, Walt Disney; Sylvère Lotringer of Columbia University; Arrow Dynamics of California, with Dal Freeman Ron Toomer; David Lewis; Cedar Point, built by Custom Coasters International of Cincinnati; Eric Westin of Walt Disney Imagineering, and the Big Thunder Mountain Railroad ride; Marc Davis, who drew Tinkerbell in Peter Pan, and who worked on the Pirates of the Caribbean ride, which opened in 1967; Larry Lester and David Codiga of Universal Studios, and their earthquake Studio Tour and Backdraft rides; Dreamland in 1912; psychologist Timothy Leary; Douglas Trumbull and the Back to the Future: The Ride and Luxor Las Vegas; Stan Kinsey of SimEx-Iwerks; Michael Ryder and Thom Dickeson of Evans & Sutherland, and texture mapping onto polygons, a main feature of transportation simulations; Bob Stone of the Advanced Robotics Research Centre at the University of Salford. Narrated by Richard O'Brien, produced by Jerome Kuehl, directed by Graham Moore, made with WGBH and Open Media 22 September The Professor's New Clothes, a re-broadcast of an Australian documentary about Professor Vishwa Jit Gupta of Panjab University and his fraudulent work about paleontology of the Himalayas. Directed by Stephen Ramsey, produced by Janet Bell, and made by Film Australia 29 September The Gambler's Guide to Winning, the ways of deploying mathematical techniques to win in gambling, with probability theory methods developed by Prof Edward O. Thorp of University of California, Irvine; the disastrous 1967 Grand National, where nearly all the horses fell at the 23rd fence; Frank Honywill George of Brunel University; Ralph Abraham of University of California, Santa Cruz; Peter A. Griffin of California State University, Sacramento; the gambler's fallacy; J. Doyne Farmer of the Santa Fe Institute. Narrated by Andrew Burt, directed by Julian Nott (son of the Conservative former defence secretary Sir John Nott, who later composed the music for Wallace and Gromit films such as The Wrong Trousers), produced by Jenny Barraclough, made by Peninsula Films 6 October Superpowers?, with Ray Hyman, about the international group of sceptics Committee for Skeptical Inquiry, who dispute topics such as UFOs, made by Open Media 13 October The Lean Burn Machine, about the development of catalytic converters for automotive engines, and how they cause more fuel to be burned than before, and the British engineer Geoffrey West who has produced an alternative, but faced restrictions from EC (EU) legislation; Europe introduced pollution legislation in July 1992; California had the worst vehicle pollution in the US, notably LA; the Clean Air Act; Rob Searles of Johnson Matthey; German environment minister Bernd Schmidbauer - Germany had over two-thirds of European car exports to the US; French physicist Hubert Curien, Minister of Higher Education, Research and Innovation from 1988 to 1993; chemistry graduate Margaret Thatcher being interviewed on 2 March 1989 on the BBC, and lean-burn engines; Bernard Bertrand, head of engine development of Peugeot; Shillington of BL; the new EC legislation in 1992 would outlaw lean-burn powered cars; Dutch automotive writer Gerard Sauer. Narrated by Nick Ross, directed by Nick Abson and Simon Broom, produced by Michael Blakstad (Editor from 1974 of Tomorrow's World), made by Workhouse 20 October The Elements, the poet Roger McGough narrates poetry for each element and how the Periodic Table came to be formed; 5% of the Earth's crust is iron; xenon is found in strobe lights; argon is in domestic incandescent light bulbs; the light bulb filament is tungsten, but reserves of tungsten are low. Directed by Ian Duncan, produced by David Dugan, made by Windfall Films (part of Argonon). Shown on 25 November 1992 on The Nature of Things in Canada 27 October The Strange Case of Crop Circles, an update to the documentary made in 1990, looking at why the 250 crop circles that appeared in the summer, that around 50% of the circles appeared in Wiltshire; the phenomenon took off after a circle near Westbury was pictured in a local newspaper in 1980; Tim Carson charged £1 per visitor to a circle in 1990, and 7,000 visited the Eastfield Pictogram at Alton Barnes, near Milk Hill; Steve Woolgar; Sir Francis Graham-Smith of the Royal Society, who dismissed those people interested in crop circles as mixed company who talked a lot of rubbish and it was a profit-less business to get involved with people who were completely hooked on the unknown; Serena Roney-Dougal; a youthful-looking Matt Ridley of The Economist said that since episodes with nuclear power in the 1970s, people had questioned evidence that scientists had told them; physicist Terence Meaden, who founded TORRO; Yoshi-Hiko Ohtsuki of Waseda University, who researched ball lightning. Narrated by Gavin Weightman, directed by Jill Freeman, and produced by her husband Michael Wills, made by Juniper Productions 3 November Human Waste, new ways of treating excrement such as dry compost toilets, oxidation pools and greenhouses. Directed by Kate Woods (Australian), made by John Blake Associates
Darshan Ranganathan (4 June 1941 – 4 June 2001) was an organic chemist from India who was known for her work in bio-organic chemistry, including "pioneering work in protein folding." She was also recognized for her work in "supramolecular assemblies, molecular design, chemical simulation of key biological processes, synthesis of functional hybrid peptides and synthesis of nanotubes."
Sources: en.wikipedia.org
=== Gray hair === Low levels of catalase may play a role in the graying process of human hair. Hydrogen peroxide is naturally produced by the body and broken down by catalase. Hydrogen peroxide can accumulate in hair follicles and if catalase levels decline, this buildup can cause oxidative stress and graying. These low levels of catalase are associated with old age. Hydrogen peroxide interferes with the production of melanin, the pigment that gives hair its color.
The Bellagio Center operates both a conference center and a residency program. Numerous Nobel laureates, Pulitzer winners, National Book Award recipients, Prince Mahidol Award winners, and MacArthur fellows, as well as several acting and former heads of state and government, have been in residence at Bellagio.
Morpholino Also phosphorodiamidate Morpholino oligomer. A synthetic nucleic acid analogue connecting a short sequence of nucleobases into an artificial antisense oligomer, used in genetic engineering to knockdown gene expression by pairing with complementary sequences in naturally occurring RNA or DNA molecules, especially mRNA transcripts, thereby inhibiting interactions with other biomolecules such as proteins and ribosomes. Morpholino oligomers are not themselves translated, and neither they nor their hybrid duplexes with RNA are attacked by nucleases; also, unlike the negatively charged phosphates of normal nucleic acids, the synthetic backbones of Morpholinos are electrically neutral, making them less likely to interact non-selectively with a host cell's charged proteins. These properties make them useful and reliable tools for artificially generating mutant phenotypes in living cells.
Romania has a democratic, multi-party system, with legislative power vested in the government and the two chambers of the Parliament, more specifically the Chamber of Deputies and the Senate. The judiciary is independent of the executive and the legislature. The latter is elected by popular vote for a maximum of two terms of five years and appoints the prime minister who in turn appoints the Council of Ministers. The legislative branch of the government, collectively known as the Parliament (residing at the Palace of the Parliament), consists of two chambers (Senate and Chamber of Deputies) whose members are elected every four years by simple plurality. The justice system is independent of the other branches of government and is made up of a hierarchical system of courts with the High Court of Cassation and Justice being the supreme court of Romania. There are also courts of appeal, county courts and local courts. The Romanian judicial system is strongly influenced by the French model, is based on civil law and is inquisitorial in nature. The Constitutional Court (Curtea Constituțională) is responsible for judging the compliance of laws and other state regulations with the constitution, which is the fundamental law of the country and can be amended only through a public referendum. Romania's 2007 entry into the EU has been a significant influence on its domestic policy, and including judicial reforms, increased judicial cooperation with other member states, and measures to combat corruption. The Economist Intelligence Unit rated Romania as a "flawed democracy" in 2025.
Sources: en.wikipedia.org
HPLC separates and detects individual compounds in a liquid sample, producing peaks at characteristic retention times. Peak area or height can be used to estimate concentration when calibrated with known standards. It does not identify unknown compounds with certainty unless additional detectors or reference materials are used.
Pressure drives the liquid mobile phase through a column packed with small particles. Without pressure, flow would be very slow or stop because the packed bed resists liquid movement. Modern pumps maintain a steady flow despite the resistance.
A chromatogram is a plot of detector signal against time after sample injection. Each peak represents a compound or group of compounds eluting from the column. Retention time and peak area are the main measurements read from the plot.
It measures the amounts and identities of compounds in liquid samples by separation and detection. Depending on the detector and reference standards, results can be qualitative or quantitative. The technique is used in fields such as pharmaceutical analysis, food safety, and environmental monitoring.