Everything below concerns system suitability. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-11-28. Numbers and descriptions here follow the published literature rather than marketing material.
Several separation modes exist, including reversed-phase, normal-phase, ion-exchange, size-exclusion, and hydrophilic interaction liquid chromatography. Reversed-phase uses a nonpolar stationary phase with a polar mobile phase and is widely applied to small organic molecules. Gradient elution changes mobile phase composition during the run, while isocratic elution keeps it constant. Column chemistry, particle size, temperature, flow rate, and mobile phase pH all influence retention and resolution. Method development selects conditions that separate analytes from matrix components and from each other.
Detection commonly uses ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. Ultraviolet detection depends on molecular chromophores that absorb light at specific wavelengths. Mass spectrometry provides mass information and sensitive quantification, often after electrospray ionization. Before sample batches, performance checks examine resolution, elution time repeatability, peak symmetry, and plate count. Matrix effects and co-elution remain recognized uncertainties; formal validation studies and orthogonal detection help address them. Detector choice depends on analyte properties and required sensitivity.
HPLC testing separates dissolved compounds by passing a liquid sample through a column packed with stationary phase. A pump delivers mobile phase at controlled flow, and the sample components interact differently with stationary and mobile phases. Compounds that spend more time in mobile phase elute earlier; those retained by stationary phase elute later. Detectors record elution as peaks, and peak area or height relates to amount. This mechanism underpins quantitative analysis of mixtures.
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 |
|---|---|---|
| Column particle size | 3–5 µm for conventional HPLC; sub-2 µm for UHPLC | Smaller particles increase backpressure and efficiency. |
| Typical flow rate | 0.5–2.0 mL/min for a 4.6 mm internal diameter column | Flow scales with column diameter and particle size. |
| UV detection wavelength | 190–400 nm | Selection depends on analyte chromophore. |
| Column temperature | 25–40 °C | Temperature affects retention, selectivity, and pressure. |
| Injection volume | 1–20 µL | Larger volumes may distort early-eluting peaks. |
Routine quality control uses system suitability, blank injections, check standards, and control samples to detect drift or contamination. System suitability criteria may specify minimum resolution, maximum tailing factor, and a permitted range for repeated injections. Blank injections reveal carryover or solvent contamination, while check standards confirm calibration accuracy over a batch. Control samples with known analyte levels can show whether results remain within statistical limits. When a control result falls outside limits, the analyst investigates the cause and may invalidate affected results before repeating the batch.
Documentation and traceability are central to regulated HPLC testing. Records typically include instrument logs, column history, mobile-phase preparation, sample preparation, injection sequences, raw chromatograms, and audit trails. Electronic systems may require user access controls, time-stamped changes, and backup procedures. Training records show that analysts are qualified for assigned methods. Audits and inspections check whether written procedures match actual practice and whether deviations are documented. These controls support reproducibility and allow results to be reconstructed if questions arise later.
Method validation establishes that an HPLC procedure is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, robustness, and solution stability. Accuracy reflects closeness to a reference value, while precision reflects agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from matrix components. Validation is documented through protocols and reports, and the required extent depends on the method's use and regulatory context.
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.
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.
Territories have long been shared between peoples, and individuals have often identified themselves within networks of relationships rather than as subjects of a particular state sovereign." Basing citizenship off the Dawes Rolls and other rolls is what scholar Fay A. Yarbrough calls "dramatically different from older conceptions of Cherokee identity based on clan relationships, in which individuals could be fully Cherokee without possessing any Cherokee ancestry" and that by the tribe later "developing a quantifiable definition of Cherokee identity based on ancestry", this "would dramatically affect the process of enrollment late in the nineteenth century and the modern procedure of obtaining membership in the Cherokee Nation, both of which require tracing an individuals' lineage to a 'Cherokee by blood.'" Thus, the Dawes Roll itself still upholds "by blood" language and theory. Mark Edwin Miller acknowledges in his work that many of descent people left the tribes and "assimilated into existing, non-tribal (if also nonwhite) communities," and thus, without a tribe, cannot be recognized by the BIA. Miller also states that even "so-called purely 'descendancy' tribes such as the Five Tribes with no blood quantum requirement jealously guard some proven, documentary link by blood to distant ancestors. More than any single BIA requirement, however, this criterion has proven troublesome for southeastern groups [seeking federal recognition] because of its reliance on non-Indian records and the confused (and confusing) nature of surviving documents."
=== Other uses in science and technology === Link (Mars), a rock outcrop Link or linking col, used in determining topographic prominence Telecommunications link, communication channel between two or more devices LINK, a spacecraft used in the Swift rescue mission
== Other uses == Contraction (economics), a general slowdown in economic activity; the opposite of economic expansion Contraction (physics), change in the volume of matter in response to a change in temperature Lanthanide contraction, the decrease in size of the ionic radius of lanthanide elements with their growing atomic number Contracted (film), a 2013 horror thriller film by Eric England and its sequel Contracted: Phase II (2015) which directed by Josh Forbes
Sources: en.wikipedia.org
== Production == Most 131I production is from neutron irradiation of a natural tellurium target in a nuclear reactor. Irradiation of natural tellurium produces almost entirely 131I as the only radionuclide with a half-life longer than hours (and shorter than millions of years), since lighter isotopes of tellurium become heavier stable isotopes, or else stable antimony or iodine. However, the heaviest naturally occurring tellurium nuclide, 130Te (34% of natural tellurium) absorbs a neutron to become tellurium-131, which beta decays with a half-life of 25 minutes to 131I. A tellurium compound can be irradiated while bound as an oxide to an ion exchange column, with evolved 131I then eluted into an alkaline solution. More commonly, powdered elemental tellurium is irradiated and then 131I separated from it by dry distillation of the iodine, which has a far higher vapor pressure. The element is then dissolved in a mildly alkaline solution in the standard manner, to produce 131I as iodide and hypoiodate (which is soon reduced to iodide). 131I is a fission product with a yield of 2.878% from uranium-235, and can be released in nuclear weapons tests and nuclear accidents. However, the short half-life means it is not present in significant quantities in cooled spent nuclear fuel, unlike iodine-129 whose half-life is nearly a billion times that of 131I. It is discharged to the atmosphere in small quantities by some nuclear power plants.
In the Bronze Age, the Hellenes had trade and cultural contacts with Egypt. Before the time that Alexander the Great occupied Egypt, the Greek name, sphinx, was already applied to these statues. The historians and geographers of Greece such as Herodotus wrote extensively about Egyptian culture. There was a single sphinx in Greek mythology, a unique demon of destruction and bad luck. Apollodorus describes the sphinx as having a woman's face, the body and tail of a lion and the wings of a bird. Pliny the Elder mentions that Ethiopia produces plenty of sphinxes, with brown hair and breasts, corroborated by 20th-century archeologists. Statius describes her as a winged monster, with pallid cheeks, eyes tainted with corruption, plumes clotted with gore and talons on livid hands. John Tzetzes described her as having the front of a lion, the rear of a human, the wings of a griffin and the claws of an eagle. Sometimes, the wings are specified to be those of an eagle, and the tail to be serpent-headed. According to Hesiod, the Sphinx was a daughter of Orthrus and an unknown she—either the Chimera, Echidna, or Ceto. According to Apollodorus and Lasus, she was a daughter of Echidna and Typhon. The sphinx was the emblem of the ancient city-state of Chios, and appeared on seals and the obverse side of coins from the 6th century BC until the 3rd century AD.
== History == The suspensory muscle of the duodenum was first named in 1853 by Václav Treitz, as the musculus suspensorius duodeni (in Latin), and described as consisting of a lower muscular portion with a broad base, and an upper tendinous portion blending with connective tissue around the origins of the superior mesenteric and coeliac arteries. It is commonly termed the ligament of Treitz by clinicians and as the suspensory muscle of the duodenum by anatomists. It has also been likened to "a polar ice cap ... a structure that many refer to but few have seen."
Bioelectrical impedance analysis (BIA) Computed tomography (CT scans) Dual-energy X-ray absorptiometry (DEXA) Magnetic resonance imaging (MRI) However, these methods are not widely used because they can be expensive and difficult to access.
Sources: en.wikipedia.org
== Mechanism of action == Despite its name (ending in -omycin) Fosfomycin is not a macrolide, but a member of a novel class of phosphonic antibiotics. Fosfomycin is bactericidal and inhibits bacterial cell wall biogenesis by inactivating the enzyme UDP-N-acetylglucosamine-3-enolpyruvyltransferase, also known as MurA. This enzyme catalyzes the committed step in peptidoglycan biosynthesis, namely the ligation of phosphoenolpyruvate (PEP) to the 3'-hydroxyl group of UDP-N-acetylglucosamine. This pyruvate moiety provides the linker that bridges the glycan and peptide portion of peptidoglycan. Fosfomycin is a PEP analog that inhibits MurA by alkylating an active site cysteine residue (Cys 115 in the Escherichia coli enzyme). Fosfomycin enters the bacterial cell through the glycerophosphate transporter.
A Ramachandran plot (also known as a Ramachandran diagram or a [φ,ψ] plot), originally developed in 1963 by G. N. Ramachandran, C. Ramakrishnan, and V. Sasisekharan, is a way to visualize energetically allowed regions for backbone dihedral angles ψ against φ of amino acid residues in protein structure. In a protein chain three dihedral angles are defined:
Culver's soon shifted its attention to developing markets beyond the Midwest, and opened the first franchise outside the region in Texas in February 1998. The current franchising strategy is one of strategic expansion. The chain expanded into Colorado Springs, Colorado and Cheyenne, Wyoming in 2005, followed by an opening in Bowling Green, Kentucky in July 2006. Locations traditionally had a 120-seat format through much of Culver's expansion. The Metro-98 prototype was developed in 2006 and first constructed in Fort Dodge, Iowa. While the new layout has less seating to offer guests, it also reduced the amount of land needed for construction by around 20%. The company expanded to the Phoenix metropolitan area in 2008. The first franchise in Utah opened in Midvale in 2011, when a couple from Wisconsin relocated there. They signed a development agreement for four locations in the southern half of Salt Lake County. By the end of 2011, 445 Culver's restaurants were open in 19 states. They opened in South Carolina in 2012; Florida, Georgia, and Tennessee in 2014; and North Carolina in 2015. A location was announced for Alabama in June 2018, and expansion continued into Arkansas in January 2022. In February 2026, Culver's announced plans to enter the Virginia market, starting with their first location in the Richmond area.
== Knowledge of society == The Ipsos Perils of Perception 2018 study purports to measure "... which key facts [issues and facts about their nation] the online public across 37 countries get right about their society—and which they get wrong .... the survey aims to highlight how we're wired to think in certain ways and how our environment influences our (mis)perceptions." Thailand ranked number one in the 2018 survey (1=least accurate perceptions; 37=most accurate perceptions) meaning Thais were least knowledgeable about their society compared with citizens of 36 other nations. Other Asian nations ranked were: Malaysia, 4; China, 9; India, 12; Japan, 16; South Korea, 24; Singapore, 31; and the most knowledgeable citizenry, Hong Kong, 37.
Two different Dromaius species were present in Australia at the time of European settlement, and one additional species is known from fossil remains. The insular dwarf emus, D. n. baudinianus and D. n. minor, originally present on Kangaroo Island and King Island respectively, both became extinct shortly after the arrival of Europeans. D. n. diemenensis, another insular dwarf emu from Tasmania, became extinct around 1865. The mainland subspecies, D. n. novaehollandiae, remains common. The population of these birds varies from decade to decade, largely being dependent on rainfall; in 2009, it was estimated that there were between 630,000 and 725,000 birds. Emus were introduced to Maria Island off Tasmania, and Kangaroo Island off the coast of South Australia, during the 20th century. The Maria Island population died out in the mid-1990s. The Kangaroo Island birds have successfully established a breeding population. In 1912, the Australian ornithologist Gregory M. Mathews recognised three living subspecies of emu, D. n. novaehollandiae (Latham, 1790), D. n. woodwardi Mathews, 1912 and D. n. rothschildi Mathews, 1912. The Handbook of the Birds of the World, however, argues that the last two of these subspecies are invalid; natural variations in plumage colour and the nomadic nature of the species make it likely that there is a single race in mainland Australia. Examination of the DNA of the King Island emu shows this bird to be closely related to the mainland emu and hence best treated as a subspecies.
Sources: en.wikipedia.org
HPLC separates and quantifies compounds in a liquid sample. Detectors produce a response proportional to the amount of a compound passing through the flow cell. Identification by retention time requires comparison with a known standard.
UHPLC uses columns with smaller particles and operates at higher pressures than conventional HPLC. These conditions can improve speed, resolution, and sensitivity. Both techniques use the same fundamental separation principles.
Validation shows that a method performs reliably for its intended purpose across a defined range. It assesses accuracy, precision, specificity, linearity, and robustness. Regulated testing often requires documented validation before routine use.
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.