The short version of Mobile phase fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-05-16. Anything still debated is marked as such rather than presented as settled.
Practical HPLC testing depends on careful sample preparation and instrument maintenance. Samples may require filtration, dilution, pH adjustment, or extraction to avoid column damage and matrix interference. Mobile phases are degassed and filtered, and columns are equilibrated before injection. Common problems include peak tailing, baseline drift, ghost peaks, carryover, and co-elution of analytes. Documentation of instrument logs, calibration records, and electronic audit trails supports data integrity and traceability. Ongoing training and routine maintenance help reduce variability between analysts and laboratories.
Quality control laboratories use HPLC to check identity, purity, concentration, and stability of raw materials and finished products. A validated method specifies the column, mobile phase, flow rate, detection wavelength, injection volume, and run time. Samples are prepared and compared against reference standards of known concentration. The resulting chromatogram provides quantitative data, such as assay values and impurity levels. This approach is common in pharmaceutical, food, environmental, and industrial testing where consistent measurements are required.
Method validation evaluates accuracy, precision, specificity, linearity, range, detection limit, quantitation limit, and robustness. Regulatory guidance for pharmaceuticals, foods, and environmental testing defines expected documentation and acceptance criteria. Verification confirms that a validated method works in a specific laboratory with its own instruments and reagents. Calibration curves use reference standards with known purity and traceability, while measurement uncertainty is estimated from validation data, control charts, and collaborative studies. The scope of validation depends on the method's intended use.
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.
| Parameter | Typical acceptance criterion | Notes |
|---|---|---|
| Resolution | ≥ 1.5 | Baseline separation of adjacent peaks |
| Tailing factor | ≤ 2.0 | Peak symmetry measure |
| Theoretical plates | > 2000 | Column efficiency indicator |
| Injection repeatability | ≤ 2% RSD | Relative standard deviation for replicate injections |
| Linearity | r² ≥ 0.995 | Calibration curve over the working range |
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.
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.
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.
=== DuPont and the invention of nylon === Researchers at DuPont began developing cellulose-based fibers, culminating in the synthetic fiber rayon. DuPont's experience with rayon was an important precursor to its development and marketing of nylon. DuPont's invention of nylon spanned an eleven-year period, ranging from the initial research program in polymers in 1927 to its announcement in 1938, shortly before the opening of the 1939 New York World's Fair. The project grew from a new organizational structure at DuPont, suggested by Charles Stine in 1927, in which the chemical department would be composed of several small research teams that would focus on "pioneering research" in chemistry and would "lead to practical applications". Harvard instructor Wallace Hume Carothers was hired to direct the polymer research group. Initially he was allowed to focus on pure research, building on and testing the theories of German chemist Hermann Staudinger. He was very successful, as research he undertook greatly improved the knowledge of polymers and contributed to the science. Nylon was the first commercially successful synthetic thermoplastic polymer. DuPont began its research project in 1927. The first nylon, nylon 66, was synthesized on February 28, 1935, by Wallace Hume Carothers at DuPont's research facility at the DuPont Experimental Station. In response to Carothers' work, Paul Schlack at IG Farben developed nylon 6, a different molecule based on caprolactam, on January 29, 1938. In the spring of 1930, Carothers and his team had already synthesized two new polymers.
Later work making use of molecular evidence, with or without the use of morphological evidence, had by 2000 failed to resolve the argument. In 2011, on further molecular evidence, Janies and colleagues noted that the phylogeny of the echinoderms "has proven difficult", and that "the overall phylogeny of extant echinoderms remains sensitive to the choice of analytical methods". They presented a phylogenetic tree for the living Asteroidea only; using the traditional names of starfish orders where possible, and indicating "part of" otherwise, the phylogeny is shown below. The Solasteridae are split from the Velatida, and the old Spinulosida is broken up.
== Diagnosis == The clinical definition of ordinary smallpox is an illness with acute onset of fever followed by a rash characterized by firm, deep-seated vesicles or pustules in the same stage of development without other apparent cause. Before the availability of laboratory testing, doctors could diagnose smallpox by touch alone, due to the distinctively hard pustules. Microscopically, poxviruses produce characteristic cytoplasmic inclusion bodies, the most important of which are known as Guarnieri bodies, and are the sites of viral replication. Guarnieri bodies are readily identified in skin biopsies stained with hematoxylin and eosin, and appear as pink blobs. They are found in virtually all poxvirus infections but the absence of Guarnieri bodies could not be used to rule out smallpox. The diagnosis of an orthopoxvirus infection can also be made rapidly by electron microscopic examination of pustular fluid or scabs. All orthopoxviruses exhibit identical brick-shaped virions by electron microscopy. Definitive laboratory identification of variola virus involved growing the virus on chorioallantoic membrane (part of a chicken embryo) and examining the resulting pock lesions under defined temperature conditions. Strains were characterized by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Serologic tests and enzyme linked immunosorbent assays (ELISA), which measured variola virus-specific immunoglobulin and antigen were also developed to assist in the diagnosis of infection.
== In culture == The jalapeño is a Mexican chili but was designated by the Texas Legislature as the official "State Pepper of Texas" in 1995. In Mexico, jalapeños are used in many forms such as in salsa, pico de gallo, or grilled jalapeños. Jalapeños were included as food on the Space Shuttle as early as 1982. Guinness World Records recognizes Alfredo Hernandes for the most jalapeños eaten in a minute: 16, on 17 September 2006 at the La Costeña Feel the Heat Challenge in Chicago, Illinois. Patrick Bertoletti holds the Major League Eating jalapeño records at 275 pickled jalapeños in 8 minutes on 1 May 2011, and 191 pickled jalapeños in 6.5 minutes on 16 September 2007 in the 'Short-Form'. Joaquín Guzmán, also known as "El Chapo", the leader of the Sinaloa Cartel, operated a cannery in Guadalajara producing "Comadre Jalapeños" in order to ship cocaine to the US. The official mascot of the 1986 FIFA World Cup was Pique, a jalapeño pepper, characteristic of Mexican cuisine, with a moustache, a Colimote sombrero, and Mexican football team colors. Its name comes from picante, a Spanish word meaning "spicy", and was also a pun on the "PK" abbreviation of the football term penalty kick. Pique is also a common Spanish name. September 5th is recognized as National Jalapeno Day.
Sources: en.wikipedia.org
The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound. Helium II also exhibits a creeping effect. When a surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity. Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin. As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the van der Waals force. These waves are known as third sound.
In the 16th century, European slave traders had begun to bring enslaved Africans to the Americas. Spain was the only European power that did not establish factories in Africa to purchase slaves; the Spanish Empire instead relied on the asiento system, awarding merchants from other European nations the license to trade enslaved peoples to their overseas territories. This system brought Africans to Colombia, although many spoke out against the institution. The indigenous peoples could not be enslaved because they were legally subjects of the Spanish Crown. To protect the indigenous peoples, several forms of land ownership and regulation were established by the Spanish colonial authorities: resguardos, encomiendas and haciendas. However, secret anti-Spanish discontentment was already brewing for Colombians since Spain prohibited direct trade between the Viceroyalty of Peru, which included Colombia, and the Viceroyalty of New Spain, which included the Philippines, the source of Asian products like silk and porcelain which was in demand in the Americas. Illegal trade between Peruvians, Filipinos, and Mexicans continued in secret, as smuggled Asian goods ended up in Córdoba, Colombia, the distribution center for illegal Asian imports, due to the collusion between these peoples against the authorities in Spain. They settled and traded with each other while disobeying the forced Spanish monopoly.
== History == Robert Vince and Susan Daluge along with Mei Hua, a visiting scientist from China, developed the medication in the '80s. Abacavir was approved by the US Food and Drug Administration (FDA) in December 1998 and is the fifteenth approved antiretroviral drug in the United States.
Degradation of an amino acid often begins with transamination, in which its amino group is transferred to α-ketoglutarate, forming glutamate. This process involves transaminases, often the same enzymes used in amino acid synthesis. In many vertebrates, the amino group is subsequently released as ammonia and converted to urea via the urea cycle for excretion. However, amino acid degradation can result in uric acid or ammonia instead, depending on the organism. For example, serine dehydratase converts serine directly to pyruvate and ammonia. After removal of one or more amino groups, the remaining carbon skeleton of an amino acid can serve as a precursor for synthesizing other amino acids, be further metabolized for energy after conversion into intermediates of glycolysis (typically via gluconeogenesis) or of the citric acid cycle, or be used for fatty acid synthesis and storage as triacylglycerol. Amino acids are bidentate ligands, forming transition metal amino acid complexes.
Caspase recruitment domain-containing protein 11 also known as CARD-containing MAGUK protein 1 (Carma 1) is a protein in the CARD-CC protein family that in humans is encoded by the CARD11 gene. CARD 11 is a membrane associated protein that is found in various human tissues, including the thymus, spleen, liver, and peripheral blood leukocytes. Similarly, CARD 11 is also found in abundance in various lines of cancer cells.
Sources: en.wikipedia.org
α-neptunium takes on an orthorhombic structure, resembling a highly distorted body-centered cubic structure. Each neptunium atom is coordinated to four others and the Np–Np bond lengths are 260 pm. It is the densest of all the actinides and the fifth-densest of all naturally occurring elements, behind only rhenium, platinum, iridium, and osmium. α-neptunium has semimetallic properties, such as strong covalent bonding and a high electrical resistivity, and its metallic physical properties are closer to those of the metalloids than the true metals. Some allotropes of the other actinides also exhibit similar behaviour, though to a lesser degree. The densities of different isotopes of neptunium in the alpha phase are expected to be observably different: α-235Np should have density 20.303 g/cm3; α-236Np, density 20.389 g/cm3; α-237Np, density 20.476 g/cm3. β-neptunium takes on a distorted tetragonal close-packed structure. Four atoms of neptunium make up a unit cell, and the Np–Np bond lengths are 276 pm. γ-neptunium has a body-centered cubic structure and has Np–Np bond length of 297 pm. The γ form becomes less stable with increased pressure, though the melting point of neptunium also increases with pressure. The β-Np/γ-Np/liquid triple point occurs at 725 °C and 3200 MPa.
The secretin-cholecystokinin test (aka Secretin-CCK test, Secretin-Pancreozymin test) is a combination of the secretin test and the cholecystokinin test and is used to assess the function of both the pancreas and gall bladder.
The latter had expelled the Umayyads from the Hejaz and among the exiles to Syria was Marwan ibn al-Hakam, an Umayyad elder. Ubayd Allah persuaded Marwan, who was preparing to recognize Ibn al-Zubayr's sovereignty, to enter his candidacy as Mu'awiya II's successor. The Umayyads' principal Syrian allies, the Banu Kalb, had sought to maintain Umayyad rule and nominated Mu'awiya II's half-brother Khalid as caliph. However, the other pro-Umayyad Syrian tribes viewed Khalid as too young and inexperienced, and rallied around Marwan, who was ultimately chosen as caliph.
=== Carnivores === Strict carnivores manage vitamin A differently than omnivores and herbivores. Carnivores are more tolerant of high intakes of retinol because those species have the ability to excrete retinol and retinyl esters in urine. Carnivores also have the ability to store more in the liver, due to a higher ratio of liver HSCs to hepatocytes compared to omnivores and herbivores. For humans, liver content can range from 20 to 30 μg/gram wet weight. Notoriously, polar bear liver is acutely toxic to humans because content has been reported in range of 2,215 to 10,400 μg/g wet weight. As noted, in humans, retinol circulates bound to RBP4. Carnivores maintain R-RBP4 within a tight range while also having retinyl esters in circulation. Bound retinol is delivered to cells while the esters are excreted in the urine. In general, carnivore species are poor converters of ionone-containing carotenoids, and pure carnivores such as felidae (cats) lack the cleaving enzyme entirely. They must have retinol or retinyl esters in their diet.
Austria achieved some initial victories against the thinly spread army of Marshal Berthier. Napoleon left Berthier with only 170,000 men to defend France's entire eastern frontier (in the 1790s, 800,000 men had carried out the same task, but holding a much shorter front). In the east, the Austrians drove into the Duchy of Warsaw but did not achieve their objectives at the Battle of Raszyn on 19 April 1809. The Army of the Duchy of Warsaw captured West Galicia following its earlier success. Napoleon assumed personal command and bolstered the army for a counter-attack on Austria. After a few small battles, the well-run campaign forced the Austrians to withdraw from Bavaria, and Napoleon advanced into Austria. His hurried attempt to cross the Danube resulted in the major Battle of Aspern-Essling (22 May 1809) – Napoleon's first significant tactical defeat. But the Austrian commander, Archduke Charles, failed to follow up on his indecisive victory, allowing Napoleon to prepare and seize Vienna in early July. He defeated the Austrians at Wagram, on 5–6 July. (It was during the middle of that battle that Marshal Bernadotte was stripped of his command after retreating contrary to Napoleon's orders. Shortly thereafter, Bernadotte took up the offer from Sweden to fill the vacant position of Crown Prince there. Later he actively participated in wars against his former Emperor.)
Sources: en.wikipedia.org
Method validation is the documented process of confirming that an HPLC procedure is suitable for its intended use. It evaluates accuracy, precision, specificity, linearity, range, detection limits, and robustness. Validation criteria depend on the regulatory context and the sample type.
System suitability tests are short checks performed before or during an HPLC run to verify instrument and method performance. They often include resolution, tailing factor, theoretical plates, and injection precision. Results must meet predefined limits for sample data to be accepted.
HPLC retention time alone cannot definitively identify an unknown substance. A match with a reference standard under identical conditions provides supporting evidence. Confirmation typically requires mass spectrometry, nuclear magnetic resonance, or another orthogonal technique.
System suitability is typically performed before each batch or according to the validated method and laboratory procedure. Some long runs include periodic checks during analysis. The required frequency depends on regulatory expectations and method performance.