Everything below concerns mobile phase. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-08-29. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| 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 |
High-performance liquid chromatography testing separates components of a liquid sample by forcing a mobile phase through a packed column. The stationary phase inside the column interacts with analytes to different degrees, so each compound exits at a characteristic retention time. A pump delivers solvent at controlled flow and pressure, while an injector introduces a precise sample volume. Detectors such as ultraviolet-visible, fluorescence, refractive index, or mass spectrometric instruments record the separated bands. The resulting chromatogram provides qualitative and quantitative information about the mixture.
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.
The first reference to Israel in non-biblical sources is found in the Merneptah Stele in c. 1209 BCE. The inscription is very brief and says: "Israel is laid waste and his seed is not". The inscription refers to a people, not an individual or nation state, who inhabit central Palestine or the highlands of Samaria. Some Egyptologists suggest that Israel appeared in earlier topographical reliefs, dating to the Eighteenth Dynasty or Nineteenth Dynasty (i.e. reign of Ramesses II) , but this reading remains controversial. In the Hebrew Bible, Israel first appears in Genesis 32:29, where an angel renames Jacob to Israel after Jacob fought with him. According to the folk etymology given in the text, Israel is derived from yisra, "to prevail over" or "to struggle with", and El, a Canaanite-Mesopotamian creator god that is tenuously identified with Yahweh. However, modern scholarship interprets El as the subject, "El rules/struggles", from sarar (שָׂרַר) 'to rule' (cognate with sar (שַׂר) 'ruler', Akkadian šarru 'ruler, king'), which is likely cognate with the similar root sara (שׂרה) "fought, strove, contended". Dr. Tzemah Yoreh clarifies that Israel is a combination of 'to strive with' (ש.ר.ה) and 'God' (אל) and that Jacob's name alternates between Jacob and Israel in the biblical narrative, even after his renaming, due to the authors having different opinions about Jacob's moral character. The gradual ethnonymic shift from "Israelites" to "Jews", regardless of their descent from Judah is made explicit in the Book of Esther (4th century BCE) of the Tanakh.
Theodoric made him quaestor sacri palatii (quaestor of the sacred palace, the senior legal authority) in 507, governor of Lucania and Bruttium, consul in 514 and magister officiorum (master of offices, one of the most senior administrative officials) in 523. He was praetorian prefect (chief minister) under the successors of Theodoric: under Athalaric (Theodoric's grandson, reigned 526–34) in 533 and, between 535 and 537, under Theodahad (Theodoric's nephew, reigned 534–36) and Witiges (Theodoric's grandson-in-law, reigned, 536–40). The major works of Cassiodorus, besides the Bibles, were the Historia Gothorum, a history of the Goths, the Variae and account of his administrative career and the Institutiones divinarum et saecularium litterarum, an introduction to the study of the sacred scriptures and the liberal arts which was influential in the Middle Ages. Byzantine (Eastern Roman) Emperor Justinian I, retook Italy from the Ostrogoths between 535 and 556. He soon lost much of Italy to the Lombards between 568 and 590, but retained the south until 1059–1071, where they thrived and where the Greek language was the official and vernacular language. In Calabria towns such as Stilo and Rossano and San Demetrio Corone achieved great religious status. From the 7th century many monasteries were built in the Amendolea and Stilaro Valleys. Stilo was the destination of hermits and Basilian monks. Many Byzantine churches survive in the region.
=== General xenarthran research === McDonald et al. (2026) study the composition of the xenarthran assemblage from the Sistema Calera Cave (Mexico), reporting evidence of presence of Glyptotherium cylindricum and three sloth taxa, and report that the studied site represents the second known locality preserving fossil material of both Eremotherium and Nothrotheriops.
Crude oil and refined fuel spills from tanker ship accidents have damaged natural ecosystems and human livelihoods in Alaska, the Gulf of Mexico, the Galápagos Islands, France and many other places. The quantity of oil spilled during accidents has ranged from a few hundred tons to several hundred thousand tons (e.g., Deepwater Horizon oil spill, SS Atlantic Empress, Amoco Cadiz). Smaller spills have already proven to have a great impact on ecosystems, such as the Exxon Valdez oil spill. Oil spills at sea are generally much more damaging than those on land, since they can spread for hundreds of square miles in a thin oil slick which can cover beaches with a thin coating of oil. This can kill sea birds, mammals, shellfish, and other organisms it coats. Oil spills on land are more readily containable if a makeshift earth dam can be rapidly bulldozed around the spill site before most of the oil escapes, and land animals can avoid the oil more easily. Control of oil spills is difficult, requiring ad hoc methods and often a large amount of manpower. The dropping of bombs and incendiary devices from aircraft on the SS Torrey Canyon wreck produced poor results; modern techniques would include pumping the oil from the wreck, like in the Prestige oil spill or the Erika oil spill.
Sources: en.wikipedia.org
A number of AlphaFold clones have also been published, mostly with permissive license terms. Clones for AlphaFold3 include ByteDance's Protenix (Apache 2.0 License), AlQuraishi Laboratory's OpenFold-3 (MIT license), and Boltz-1/2 (MIT license). There are also clones for older versions, though they became less relevant with the open-source release of AlphaFold 1 and 2 source codes. Still relevant are models, both open- and closed-source, that include modifications to the AlphaFold architecture. For AlphaFold 2, a notable example is ESMFold from Meta, which replaces the multiple sequence alignment with the latent space of a protein language model. Open-source tools that complement AlphaFold have also been made. One well-cited example is ColabFold, which uses MMseqs2 instead of HHblits to speed up the sequence search, allowing the AlphaFold pipelines to run quickly on Google Colab.
229Th has a nuclear isomer, 229mTh, with an excitation energy of 8.355733554021(8) eV. This is by far the lowest of all nuclear isomers. Because this energy lies between thorium's first and second ionization energies of 6.3 and 11.5 eV, the decay rate of 229mTh is sensitive to the electronic environment of the nucleus. In neutral 229mTh, the isomer decays by internal conversion to 229Th+ within a few microseconds. However, the isomeric energy is not enough to remove a second electron, so internal conversion is impossible in 229mTh+ ions; they are forced to decay radiatively with a half-life 8.4 orders of magnitude longer, in excess of 1000 seconds. Embedded in ionic crystals, ionization is not quite 100%, so a small amount of internal conversion occurs, leading to a recently measured lifetime of ≈600 s, which can be extrapolated to a lifetime for isolated ions of 1740±50 s. Any photon emitted by nuclear decay is called a gamma ray, but this "gamma ray" has a frequency of 2020407384335±2 kHz (wavelength 148.3821828827(15) nm), in te far ultraviolet. This means it is possible to build a laser operating at this frequency, giving the only known opportunity for direct laser excitation of a nuclear state. This could have applications like a nuclear clock of very high accuracy or as a qubit for quantum computing. These applications were for a long time impeded by imprecise measurements of the isomeric energy, as laser excitation's exquisite precision makes it difficult to use to search a wide frequency range.
in a gathering or a date, are known as dining, and large dining events where many people are invited to eat food together are known as banquets or feasts. The craft of preparing and presenting meals for formal eating is called culinary arts, and the person performing such tasks is known as a cook, chef or cater depending on the respective nature of food service. Physicians and dieticians consider eating a healthy diet essential for maintaining peak physical condition. Some individuals may reduce their amount of dietary intake, which may be a result of a voluntary choice as part of dieting lifestyle or as fasting for reasons of religious food prohibition, abstinence or political protest (i.e. a hunger strike). Limited consumption or rationing may also be due to logistical reasons such as a food shortage or a famine, in which case it will lead to starvation and undernutrition. On the contrary, overeating and excessive intake of calories (overnutrition) may lead to obesity and associated health problems, and while the reasons behind it are myriad, its prevalence in the developed world has led some public health professionals to declare an "obesity epidemic".
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.
System suitability is a set of checks performed before and during a run to confirm that the instrument, column, and method work as expected. Common checks include resolution, tailing factor, theoretical plates, and relative standard deviation of replicate injections. Failure triggers troubleshooting or method adjustment.