The short version of stationary phase fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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 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.
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 |
|---|---|---|
| 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. |
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. A diode array detector records full spectra across a wavelength range, which helps identify co-eluting peaks. Mass spectrometry provides mass-to-charge ratios and can confirm molecular identity at low concentrations. The choice of detector depends on analyte structure, required sensitivity, and whether quantitation or identification is the goal. No single detector works for every compound, and method development often compares responses before selecting one.
High-performance liquid chromatography is an analytical technique that separates components of a liquid sample by passing it 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 interaction with the stationary phase cause analytes to migrate at different rates. Detectors record elution as peaks, and a data system converts signals into a chromatogram. The method is suited to compounds that dissolve in a liquid and are not volatile enough for gas chromatography.
Reversed-phase chromatography dominates modern HPLC testing, using a nonpolar stationary phase such as chemically bonded octadecyl groups and a polar mobile phase of water mixed with organic solvent. Analytes partition between the mobile and stationary phases according to hydrophobicity. Gradient elution changes the mobile phase composition over time to separate compounds with a wide range of retention. Isocratic elution keeps the composition constant and is simpler for routine assays. Column temperature, pH, and flow rate influence selectivity, peak shape, and retention time, so these parameters are controlled during a validated method.
Routine quality control monitors retention time shifts, baseline noise, system pressure, and peak shape. Trends can reveal column aging, mobile phase preparation errors, detector drift, or sample degradation. Corrective actions may include replacing the column, preparing fresh mobile phase, or recalibrating the detector. Stability testing often uses HPLC to measure parent compound loss and degradation product formation. Open questions remain about how accelerated stability results extrapolate to long-term storage under varied conditions.
Quality control for HPLC testing combines scheduled checks, documented procedures, and review of results. Before sample analysis, system suitability testing confirms that the instrument, column, and method meet predefined criteria. Common criteria include resolution between critical peaks, retention time precision, peak tailing, and theoretical plate count. Failure triggers investigation before results are reported. Records link raw data, calculations, instrument logs, and analyst identity to each batch, supporting audits and repeat analysis.
Validation establishes that a method is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, robustness, and stability of standards and samples. Acceptance criteria are defined in advance, and results are documented in a validation report. Regulatory guidance for pharmaceuticals, foods, and environmental testing differs, so the applicable framework must be identified. Ongoing verification uses control samples and trend charts after validation. Method transfer to another laboratory may require partial revalidation.
Routine quality control includes blanks, duplicates, spiked samples, and certified reference materials. Calibration curves are prepared with standards at several concentrations, and the detector response is checked for linearity. Carryover, column aging, mobile phase evaporation, and temperature drift can shift retention times or peak areas. Maintenance such as replacing seals, filters, and columns helps prevent failures. Records of injections, integration, and deviations support traceability. Audits may request raw data and instrument logs for each batch.
Developing an HPLC test begins with defining the analytes, matrix, and required reporting limits. Chemists select a separation mode, column chemistry, mobile phase composition, flow rate, and detection wavelength or mass transition. Experiments then adjust these variables to achieve adequate retention, resolution, and peak shape. System suitability tests confirm that the instrument and method perform consistently before sample analysis. Without suitable resolution, quantitative results may be unreliable. Preliminary runs often use scouting gradients to locate retention windows.
=== Non-accidental === In those hospitalized from scalds or fire burns, 3–10% are from assault. Reasons include: child abuse, personal disputes, spousal abuse, elder abuse, and business disputes. An immersion injury or immersion scald may indicate child abuse. It is created when an extremity, or sometimes the buttocks are held under the surface of hot water. It typically produces a sharp upper border and is often symmetrical, known as "sock burns", "glove burns", or "zebra stripes" - where folds have prevented certain areas from burning. Deliberate cigarette burns are most often found on the face, or the back of the hands and feet. Other high-risk signs of potential abuse include: circumferential burns, the absence of splash marks, a burn of uniform depth, and association with other signs of neglect or abuse. Bride burning, a form of domestic violence, occurs in some cultures, such as India where women have been burned in revenge for what the husband or his family consider an inadequate dowry. In Pakistan, acid burns represent 13% of intentional burns, and are frequently related to domestic violence. Self-immolation (setting oneself on fire) is also used as a form of protest in various parts of the world.
A 2022 study concluded that the practice of rinsing uncooked chicken actually increases the risk of pathogen transfer through the splashing of water droplets, with factors such as faucet height, flow type, and surface stiffness affecting the risk of cross-contamination. The most common bacterial foodborne pathogens are:
Firm tofu (called 老豆腐 lǎodòufu in Chinese; 木綿豆腐, momen-dōfu in Japanese, "cotton tofu"; 모두부, mo-dubu in Korean): Although drained and pressed, this form of fresh tofu retains a high moisture content. It has the firmness of raw meat and bounces back readily when pressed. The texture of the inside of the tofu is similar to that of a firm custard. The skin of this form of tofu retains the pattern of the muslin used to drain it, and the outside is slightly more resistant to damage than the inside. It can be picked up easily with chopsticks. A very firm type of momen-dōfu is eaten in parts of Japan, called ishi-dōfu (石豆腐, "stone tofu") in parts of Ishikawa, or iwa-dōfu (岩豆腐, "rock tofu") in Gokayama in the Toyama Prefecture and in Iya in the prefecture of Tokushima. These types of firm tofu are produced with seawater instead of nigari (magnesium chloride), or using concentrated soy milk. Some of them are squeezed using heavy weights to eliminate excess moisture. These products are produced in areas where traveling is inconvenient, such as remote islands, mountain villages, and heavy snowfall areas.
== See also == 1968 Olympics Black Power salute Apartheid-era South Africa and the Olympics British and Irish Lions Halt All Racist Tours Peter McGregor New Zealand Cavaliers South African rebel tours (cricket) South American Jaguars Sporting boycott of South Africa during the Apartheid era
Sources: en.wikipedia.org
== Metabolism == Levamisole is readily absorbed from the gastrointestinal tract and metabolized in the liver. Its time to peak plasma concentration is 1.5–2 hours. The plasma elimination half-life is fairly quick at 3–4 hours which can contribute to not detecting levamisole intoxication. The metabolite half-life is 16 hours. Levamisole's excretion is primarily through the kidneys, with about 70% being excreted over 3 days. Only about 5% is excreted as unchanged levamisole. Drug testing of racehorse urine has led to the revelation that among levamisole equine metabolites are both pemoline and aminorex, stimulants that are forbidden by racing authorities. Further testing confirmed aminorex in human and canine urine, meaning that both humans and dogs also metabolize levamisole into aminorex, though it is unclear whether plasma aminorex is present at any appreciable level. Blood samples following oral administration of levamisole out to 172 hr post-dose did not demonstrate any plasma aminorex levels above that of the limit of quantification (LoQ). Additionally, in cocaine-positive plasma samples, of which 42% contained levamisole, aminorex was never reported at concentrations higher than LoQ.
=== Molecular biology === Sequencing is used in molecular biology to study genomes and the proteins they encode. Information obtained using sequencing allows researchers to identify changes in genes and noncoding DNA (including regulatory sequences), associations with diseases and phenotypes, and identify potential drug targets.
== Casting choices == Tom Cruise, Johnny Depp, Brad Pitt, Nicolas Cage, Brandon Lee and Leonardo DiCaprio were approached for the role. Will Smith, who turned down the role to make Wild Wild West, later said he regretted the decision. Ewan McGregor was said to have been sent the script to the movie, but later turned it down and moved on to do Star Wars: Episode I – The Phantom Menace. Sandra Bullock was asked by the film's producers to star in the film, thus changing the gender of the character to female, only to receive a negative answer by Bullock.
== General care == The skin is the largest organ in the human body, protecting against pathogens, irritants, ultraviolet light, and mechanical injury, while also regulating temperature and water release as perspiration. Simple habits like washing and applying lotion may provide benefit, but little is known scientifically about the clinical efficacy of these practices. Skin care routines, even in hospitals and medical facilities, may be based on personal beliefs, preferences, and local circumstances rather than current evidence or best practices.
== Challenges == A McKinsey study claims retail productivity in India is very low compared to international peer measures. For example, the labour productivity in Indian retail was just 6% of the labour productivity in United States in 2010. India's labour productivity in food retailing is about 5% compared to Brazil's 14%; while India's labour productivity in non-food retailing is about 8% compared to Poland's 25%. Total retail employment in India, both organised and unorganised, account for about 6% of Indian labour work force currently - most of which is unorganised. This about a third of levels in United States and Europe; and about half of levels in other emerging economies. A complete expansion of retail sector to levels and productivity similar to other emerging economies and developed economies such as the United States would create over 50 million jobs in India. Training and development of labour and management for higher retail productivity is expected to be a challenge.
Sources: en.wikipedia.org
=== Canada === Under the regulation of the Canadian Food Inspection Agency, manufacturers can produce blue cheese with a maximum of 47 percent moisture and minimum of 27 percent milk fat. Salt is allowed to be used as a preservative; however, the amount of the salt or combination of salts shall not exceed 200 parts per million of milk and milk products used to make the cheese. The Canadian Food Inspection Agency does not limit the use of bacterial cultures to aid further ripening and flavoring preparations other than cheese flavoring.
=== Disannexation === In the northern Leribe District, rebel chief Joel Molapo and loyalist chief Jonathan Molapo continued to clash sporadically over the Leribe chieftaincy. Joel continuously attacked local loyalists in an effort to seize power, complicating the settlement of the Gun War. The fighting resulted in a wave of refugees fleeing towards the Orange Free State. A month later, a number of Basuto chiefs including Masopha, failed to appear at a pitso called by Orpen's successor Matt Blyth, thus rejecting Scanlen's new proposal for semi-autonomous rule. Aided by Masopha, Joel Molapo continued to massacre and destroy the properties of his opponents. During one of his raids, his warriors burnt the stone house of his deceased father, which shifted popular opinion against him. In May, Letsie I officially granted Jonathan the Leribe chieftaincy, but despite Letsie's declaration, violence in Leribe did not subside until the end of the year. Facing continued diplomatic protests from the Free State and unable to enforce the law in Basutoland, the Cape Parliament passed the Disannexation Act in September 1883. A pitso held at Maseru on 29 November resulted in most chiefs voting in favor of remaining British subjects. Masopha did not attend the Maseru pitso, holding one of his own; where he demanded complete independence. The British Secretary of State issued an Order-in-Council granting the queen's support to the Disannexation Act, which came into force on 18 March 1884.
=== Air spread === An air spread will include the breathing air supply equipment, and often a deck decompression chamber. Where a chamber is present, facilities for hyperbaric oxygen treatment are usually required. If the planned decompression is to be long, a diving stage or bell and the associated handling equipment is likely to be included to allow better control of ascent rate and decompression depth. Equipment for in-water or surface decompression on oxygen (SurDO2) may be available. Equipment may be necessary to facilitate safe entry to and exit from the water, and may include extrication equipment in case the diver is injured. A basic offshore air diving spread will typically include a dive control unit with compressor and high pressure storage banks, a launch and recovery system with a wet bell, a deck decompression chamber and a hot water unit.
=== Synthesis === Cyanuric acid (CYA) was first synthesized by Friedrich Wöhler in 1829 by the thermal decomposition of urea and uric acid. The current industrial route to CYA entails the thermal decomposition of urea, with release of ammonia. The conversion commences at approximately 175 °C (347 °F):
== Experimental setup == CV experiments are conducted on a solution in a cell fitted with electrodes. The solution consists of the solvent, in which is dissolved electrolyte and the species to be studied.
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 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.