This is a working overview of HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-01-16. Anything still debated is marked as such rather than presented as settled.
Routine HPLC testing compares a sample result with a calibration curve prepared from known reference standards. Peak area or peak height is plotted against concentration, and the curve is used to estimate unknown amounts. Retention time supports tentative identification when compared with a standard, though mass spectrometry or another confirmatory method may be needed for definitive identification. Pre-run checks verify repeatability, resolution, and peak symmetry before sample analysis. Limits of detection and quantification describe the smallest amounts that can be reliably observed or measured. Sample preparation, filtration, and degassing help prevent column damage and inconsistent results.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample. A pump moves a liquid mobile phase through a column packed with a solid stationary phase. Compounds interact differently with both phases and travel at different rates, leaving the column at distinct retention times. A detector records these arrivals as peaks on a chromatogram. The resulting pattern supports identification and quantification of substances in mixtures. Modern instruments use high pressure to force solvent through small particles, which improves speed and resolution compared with older low-pressure liquid chromatography methods.
Separation in HPLC depends on the chemistry of the stationary phase, the composition of the mobile phase, and the physical properties of the column. Reverse-phase separations use a nonpolar stationary phase and a polar mobile phase, and they are common for many organic compounds. Ion-exchange, size-exclusion, and normal-phase modes serve other classes of analytes. Gradient elution changes solvent strength over time, while isocratic elution holds it constant. Flow rate, temperature, particle size, and column length all influence peak shape and resolution. Detection may use ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry, depending on the analyte and the required sensitivity.
Most routine HPLC testing uses reversed-phase columns, where the stationary phase is nonpolar and the mobile phase is a polar mixture such as water with an organic solvent. Analytes partition between the two phases according to polarity, size, and charge. Gradients that change solvent composition over time can separate compounds with broad retention ranges. Isocratic conditions keep solvent composition constant and suit simpler mixtures. The choice of column chemistry, pH, and temperature affects selectivity and peak shape.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. UV detection is widely used because many organic compounds absorb light, but it requires a chromophore. Mass spectrometry provides mass-based identification and high sensitivity for trace analytes. Each detector has trade-offs in selectivity, cost, and compatibility with mobile phases. Quantification typically uses calibration curves prepared from reference standards. Results are reported as concentration, purity, or presence above a limit.
| Property | Value | Notes |
|---|---|---|
| Common abbreviation | HPLC | High-performance liquid chromatography |
| Separation basis | Differential partitioning | Between liquid mobile phase and solid stationary phase |
| Common mode | Reverse phase | Nonpolar column, polar mobile phase |
| Typical detector | UV-Vis absorbance | Widely used for compounds with chromophores |
| Typical column particle size | 2–5 µm | Smaller particles can improve resolution |
HPLC testing is an analytical technique used to separate, identify, and quantify components in a liquid sample. It relies on a pressurized mobile phase that carries the sample through a column packed with stationary phase. Different compounds travel at different rates because of interactions with the stationary and mobile phases. The resulting signal versus time is a chromatogram. Peak position indicates identity under specified conditions, while peak area or height relates to amount.
Laboratories apply HPLC testing across pharmaceutical, food, environmental, and industrial chemistry. The method can measure active ingredients, impurities, additives, preservatives, and degradation products. Sample preparation often includes dilution, filtration, and sometimes extraction or derivatization. The choice of column, mobile phase, pH, temperature, and detector depends on the analytes and matrix. Results are compared with reference standards to assign identity and concentration. Method suitability is judged by resolution, precision, and accuracy.
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 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.
However, in prostate cancer, mutations and overexpression of the AR can accumulate in prostate gland cells which can convert bicalutamide from an antagonist of the AR into an agonist. This can result in paradoxical stimulation of prostate cancer growth with bicalutamide and is responsible for the phenomenon of the antiandrogen withdrawal syndrome, where antiandrogen discontinuation paradoxically slows the rate of prostate cancer growth. In transgender women, breast development is a desired effect of antiandrogen or estrogen treatment. Breast development and gynecomastia induced by bicalutamide is thought to be mediated by increased activation of the ER secondary to blockade of the AR (resulting in disinhibition of the ER in breast tissue) and increased levels of estradiol. In addition to fat deposition, connective tissue growth, and ductal development, bicalutamide has been found to produce moderate lobuloalveolar development of the breasts. However, full lobuloalveolar maturation necessary for lactation and breastfeeding will not occur without progestogen treatment. Bicalutamide monotherapy seems to have minimal effect on testicular spermatogenesis, testicular ultrastructure, and certain aspects of male fertility. This seems to be because testosterone levels in the testes (where ~95% of testosterone in males is produced) are extremely high (up to 200-fold higher than circulating levels) and only a small fraction (less than 10%) of the normal levels of testosterone in the testes are actually necessary to maintain spermatogenesis.
=== Conversion to esters, amides, anhydrides === Widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, acid anhydrides, and alcohols. Their conversion to esters is widely used, e.g. in the production of polyesters. Likewise, carboxylic acids are converted into amides, but this conversion typically does not occur by direct reaction of the carboxylic acid and the amine. Instead esters are typical precursors to amides. The conversion of amino acids into peptides is a significant biochemical process that requires ATP. Converting a carboxylic acid to an amide is possible, but not straightforward. Instead of acting as a nucleophile, an amine will react as a base in the presence of a carboxylic acid to give the ammonium carboxylate salt. Heating the salt to above 100 °C will drive off water and lead to the formation of the amide. This method of synthesizing amides is industrially important, and has laboratory applications as well. In the presence of a strong acid catalyst, carboxylic acids can condense to form acid anhydrides. The condensation produces water, however, which can hydrolyze the anhydride back to the starting carboxylic acids. Thus, the formation of the anhydride via condensation is an equilibrium process. Under acid-catalyzed conditions, carboxylic acids will react with alcohols to form esters via the Fischer esterification reaction, which is also an equilibrium process. Alternatively, diazomethane can be used to convert an acid to an ester.
The United Kingdom was represented by its 1st Armoured Division known as the Desert Rats. The British 1st Armoured Division fielded approximately 176 Challenger 1 tanks. British infantry rode into battle on the Warrior tracked armoured vehicle. It had reasonable armour protection and a 30mm gun. Modified versions of the vehicle included mortar carriers, MILAN antitank systems, and command and control vehicles; and the British possessed a variety of excellent light armoured vehicles built on their FV101 Scorpion chassis. British artillery was primarily American made M109 howitzers (155mm), M110 howitzers (203mm), and M270 MLRS which were compatible with American systems. Their air support consisted of Gazelle helicopters, used for reconnaissance, and the Lynx helicopter which was comparable to the American AH-1 Cobra. The British had their full contingent of engineer, logistics, and medical units. The British 1st Armoured Division was responsible for protecting the right flank of VII Corps. It was assumed by the Corps' planners the Iraqi 52nd Armored Division would counterattack VII Corps once their penetration into Iraqi defenses was discovered. The British 1st Armoured Division had two brigades (the 4th and 7th) which participated in Operation Granby, the name given to the British military operations during the 1991 Gulf War. The British 1st Armoured Division had traveled 217 miles in 97 hours. The British 1st Armoured Division had captured or destroyed about 300 Iraqi tanks and a very large number of armored personnel carriers, trucks, reconnaissance vehicles, etc.
== Toxicity == Tertiapin is a compound of the honey bee venom (apitoxin) that causes pain and signs of inflammation around the sting, but a great number of stings can be lethal (LD50 is 18-22 stings per kg for humans). An anaphylactic shock can develop if a person has an allergy to the venom. In that case even one sting can be lethal.
Sources: en.wikipedia.org
Nancy's bottom-half finish proved a false dawn as the club finished 18th in the 1985–86 season, which meant they had to win a play-off match to avoid relegation. They retained their league status with a 3–2 aggregate win against Mulhouse. The club however sold several of their best players to avoid financial predicament and provided Wenger with little funds to work with. In Wenger's final season in charge, Nancy finished 19th and were relegated to Ligue 2. Despite the setbacks, he was contacted by Monaco over their vacant managerial job. Talks had begun during the summer of 1986, but Nancy chairman Gérard Rousselot refused to release Wenger from his contract, and Monaco were not prepared to offer compensation. Once Nancy's relegation was confirmed, Wenger was permitted to leave the club by mutual consent and was confirmed as Monaco manager in 1987. Before joining Monaco, Wenger had identified several players to build his desired team. Tottenham Hotspur midfielder Glenn Hoddle, granted a free transfer, and Patrick Battiston, out of contract at Bordeaux, were signed. Striker Mark Hateley left Milan to join Monaco and was "encouraged to learn" that his fellow Englishman Hoddle would play in the same side as him. Monaco won the league in Wenger's debut season, six points ahead of runners-up Bordeaux. Although the team scored more goals in 1988–89 due to the purchase of Liberian striker George Weah, Monaco failed to retain the league and finished third behind Marseille and Paris Saint-Germain.
After the US revoked his existing B1/B2 visa in 2005 and refused to accept his application for an A2 visa, the US State Department affirmed that the visa policy remained unchanged : "(Mr Modi) is welcome to apply for a visa and await a review like any other applicant". Exploring opportunities on how to move the relationship out of a state of morose, Lisa Curtis, senior research fellow for South Asia in the Asian Studies Center of The Heritage Foundation, says that, "the U.S. must first signal its willingness and commitment to collaborating with the new government—and that it will not dwell on the controversy of the 2002 Gujarat riots, which led the U.S. to revoke Modi's visa in 2005." In 2009, the U.S. Commission for International Religious Freedom (USCIRF) report after ignoring the views and decision of independent body (SIT) set up by India's highest judiciary vehemently alleged that there was "significant evidence" linking Narendra Modi to communal riots in the state in 2002 and asked the Obama administration to continue the policy of preventing him from travelling to the United States of America . The Obama administration maintained the 2005 decision taken by the George W. Bush administration to deny Narendra Modi entry into the United States of America. The US Government says that Modi can circumvent the USCIRF sanctions regime by visiting Washington on a Heads of government A1-visa as long as he is the Prime Minister of India.
=== Cell production and degradation === In vertebrates, the various cells of blood are made in the bone marrow in a process called hematopoiesis, which includes erythropoiesis, the production of red blood cells; and myelopoiesis, the production of white blood cells and platelets. During childhood, almost every human bone produces red blood cells; as adults, red blood cell production is limited to the larger bones: the bodies of the vertebrae, the breastbone (sternum), the ribcage, the pelvic bones, and the bones of the upper arms and legs. In addition, during childhood, the thymus gland, found in the mediastinum, is an important source of T lymphocytes. The proteinaceous component of blood (including clotting proteins) is produced predominantly by the liver, while hormones are produced by the endocrine glands and the watery fraction is regulated by the hypothalamus and maintained by the kidney. Healthy erythrocytes have a plasma life of about 120 days before they are degraded by the spleen, and the Kupffer cells in the liver. The liver also clears some proteins, lipids, and amino acids. The kidney actively secretes waste products into the urine.
Sources: en.wikipedia.org
=== Control of oxidative stress === Cysteine residues from MTs can capture harmful oxidant radicals like the superoxide and hydroxyl radicals. In this reaction, cysteine is oxidized to cystine, and the metal ions which were bound to cysteine are liberated to the media. As explained in the Expression and regulation section, this Zn can activate the synthesis of more MTs. This mechanism has been proposed to be an important mechanism in the control of the oxidative stress by MTs. The role of MTs in reducing oxidative stress has been confirmed by MT Knockout mutants, but some experiments propose also a prooxidant role for MTs. In mammalian cells, spontaneous mutagenesis is caused to a large extent by oxidative DNA damage, and the occurrence of such damage can be blocked by metallothionein. Metallothionein also plays a role in hematopoietic cell differentiation and proliferation, as well as prevention of apoptosis of early differentiated cells. Induced MT levels were adversely associated with sensitivity to etoposide-induced apoptosis, signifying that MT is a potential negative controller of apoptosis.
Gindilis, there are two criteria for a signal to be called artificial: one related to the artificial nature of the source and the other related to a particular radiation, intentionally designed to ensure communication and facilitate detection. Only Type II or III civilizations can communicate using isotropic transmissions that allow omnidirectional reception. In a 1 MHz band (which requires about 1024 watts), detection of signals from a Type II civilization is possible up to 1,000 light-years away, while signals from a Type III civilization are detectable virtually throughout the observable Universe. However, building an omnidirectional transmitter powerful enough to transmit over a range of 1,000 light years would take several million years. According to V.S. Troitsky, the energy required and the limitations in its production would be two obstacles to completing this project in a reasonable time. For Zoltan Galántai, we would not be able to distinguish between an intelligent extraterrestrial signal and a signal of natural origin. Therefore, he does not believe that Type II, III or even IV civilizations can be detected. Even if humanity reaches Type IV, it will not be able to detect another supercivilization of a similar level, and we will consider their changes in the universe to be the result of natural causes. Thus, there may be many Type IV civilizations in the universe, but none of them will be able to detect the others. Moreover, the dimensions of the universe make these supercivilizations like islands far from the others, which Dyson defines as a "Carroll Universe".
== Clinical Significance == Deficiency of glutaryl-CoA dehydrogenase causes glutaric acidemia type 1, an autosomal recessive metabolic disorder.In this disorder, impaired metabolism of glutaryl-CoA is associated with elevated levels of organic acids, including glutaric acid and 3-hydroxyglutaric acid .
Blended Scotch whisky constitutes about 90% of the whisky produced in Scotland. Blended Scotch whiskies contain both malt whisky and grain whisky. Producers combine the various malts and grain whiskies to produce a consistent brand style. Notable blended Scotch whisky brands include Ballantine's, Bell's, Chivas Regal, Cutty Sark, Dewar's, Grant's, J&B, Johnnie Walker, Teacher's Highland Cream, The Famous Grouse, Vat 69, Whyte and Mackay and William Lawson's. Most Blended Scotch Whiskies are made from the produce of at least two distilleries as the majority of distilleries produce only malt or grain whiskies; however a few distilleries such as Loch Lomond produce both malt and grain whisky at the same site.
Sources: en.wikipedia.org
HPLC testing measures the presence and amount of one or more compounds in a liquid sample. It separates mixture components and records detector responses as peaks, which are compared with reference standards. Results are usually reported as concentrations or relative percentages.
Retention time is the interval between sample injection and the detector response for a given compound. It depends on the compound's interactions with the stationary and mobile phases under set conditions. Matching a retention time to a standard supports tentative identification but is not always unique.
HPLC alone can separate unknown compounds and provide retention times, but it often cannot identify them with certainty. Coupling HPLC to mass spectrometry gives mass information that improves identification. Confirmation usually requires comparison with reference standards or complementary techniques.
It separates components in a liquid sample and measures their amounts using a detector. Results can indicate concentration, purity, or identity based on retention time and detector response. The technique works for mixtures that can be dissolved and filtered.