Chromatogram comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-09-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Quality control samples are inserted at intervals to monitor accuracy and precision throughout a batch. Blank samples detect contamination, while spiked samples assess recovery from the sample matrix. Calibration standards establish the relationship between detector response and concentration, and control samples are prepared independently from them whenever possible. Laboratories also participate in proficiency testing and maintain audit trails, instrument logs, and reagent records. Ongoing review of control charts can reveal trends before they cause out-of-specification results.
Method validation demonstrates that an HPLC procedure is suitable for its intended purpose. Common validation parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, and robustness. Accuracy reflects agreement with a reference value, while precision describes repeatability under defined conditions. Specificity shows whether the method can measure the analyte in the presence of impurities or matrix components. Validation documents are reviewed before a method is used for routine testing or regulatory submissions.
| Property | Value | Notes |
|---|---|---|
| Separation mode | Reversed-phase | Common for polar and moderately polar analytes |
| Typical column length | 100-250 mm | Shorter columns can reduce run time |
| Particle size | 3-5 micrometers | Smaller particles improve efficiency but raise pressure |
| Flow rate | 0.5-2.0 mL/min | Depends on column dimensions and pressure limits |
| Detection | UV-Vis absorbance | Widely used for compounds with chromophores |
HPLC testing is not a single fixed procedure; it is a family of separation modes. Reversed-phase, normal-phase, ion-exchange, size-exclusion, and affinity chromatography each suit different analyte properties. Reversed-phase methods dominate because they handle many neutral and moderately polar compounds. Detection can be optical, electrochemical, or mass spectrometric, and the detector dictates what information is available. Coupling with mass spectrometry increases selectivity and enables identification when standards are unavailable. The technique cannot separate every mixture without adjustment.
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.
Regulatory and pharmacopeial texts shape how HPLC testing is performed and documented. The International Council for Harmonisation provides validation guidance, while pharmacopeias publish general chromatography chapters and monographs for specific materials. Accreditation standards such as ISO/IEC 17025 address laboratory competence and traceability. Inspectors may review instrument qualification, analyst training, reference material control, and electronic records. Open questions include how best to validate methods for new complex products and how to handle automated data processing. Laboratories generally resolve these issues through risk assessment, method lifecycle management, and documented scientific justification.
In quality control laboratories, HPLC testing supports batch release, raw material checks, stability studies, and impurity profiling. A validated method defines sample preparation, instrument settings, calibration, and acceptance criteria. Analysts compare results with specifications and investigate out-of-specification outcomes before a batch is approved. Documentation includes chromatograms, integration records, audit trails, and reagent details. Because results influence product decisions, laboratories follow formal quality systems and data integrity rules. The exact tests and limits depend on the material, its intended use, and the applicable regulatory framework.
Method validation examines whether an HPLC procedure is suitable for its intended purpose. Common parameters include accuracy, precision, specificity, linearity, range, detection limit, quantification limit, and robustness. Accuracy describes closeness to a true or accepted value, while precision describes agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from related substances. Robustness tests small deliberate changes in flow, temperature, or solvent composition. Validation is not a one-time event; methods may need partial revalidation after changes to instruments, columns, sample handling, or specification limits. Regulatory guidance provides frameworks, but some details remain method-specific.
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.
=== Liquid crystals === DSC is used in the study of liquid crystals. As some forms of matter go from solid to liquid they go through a third state, which displays properties of both phases. This anisotropic liquid is known as a liquid crystalline or mesomorphous state. Using DSC, it is possible to observe the small energy changes that occur as matter transitions from a solid to a liquid crystal and from a liquid crystal to an isotropic liquid.
The Cabinet approved a 50,000-square-foot (4,600 m2) building at £3 per square foot in 1947 (equivalent to A$229 in 2022), but the design Florey and Sanders agreed upon was a 235,000-square-foot (21,800 m2) building at £4 per square foot (equivalent to A$306 in 2022). In 1950, the Cabinet approved £810,000 (equivalent to A$47,137,000 in 2022) for the building and £200,000 (equivalent to $11,639,000 in 2022) for equipment. People were also important, and Florey had a fairly free hand hiring his professors. He recruited Hugh Ennor as his professor of biochemistry, Adrien Albert as professor of medical chemistry, and Frank Fenner as professor of microbiology. A. F. Bunker was appointed the laboratory manager, and he outfitted the building. Florey visited Canberra in March 1953, but he made it clear that he did not wish to continue as acting director of the John Curtin School of Medical Research, nor take up the position of director, although he reluctantly agreed to continue as an advisor. He was pessimistic about the project, writing home to Jennings that "it will be a miracle if this place can be given a real university atmosphere". By this time the project was in jeopardy; while the prime minister, Robert Menzies, supported it, a faction in the Cabinet led by Richard Casey and Wilfrid Kent Hughes did not; they were chagrined that it was named after a man they despised, and that it called itself a school when it would not train doctors. Changing the name required amending the act, and this did not occur.
All darmstadtium isotopes are extremely unstable and radioactive; in general, the heavier isotopes are more stable than the lighter. The most stable known darmstadtium isotope, 281Ds, is also the heaviest known darmstadtium isotope; it has a half-life of 14 seconds. The isotope 279Ds has a half-life of 0.18 seconds, while the unconfirmed 281mDs has a half-life of 0.9 seconds. The remaining isotopes and metastable states have half-lives between 1 microsecond and 70 milliseconds. Some unknown darmstadtium isotopes may have longer half-lives, however. Theoretical calculation in a quantum tunneling model reproduces the experimental alpha decay half-life data for the known darmstadtium isotopes. It also predicts that the undiscovered isotope 294Ds, which has a magic number of neutrons (184), would have an alpha decay half-life on the order of 311 years; exactly the same approach predicts a ~350-year alpha half-life for the non-magic 293Ds isotope, however.
=== Recreational use === Zopiclone has the potential for non-medical use, dosage escalation, and drug dependence. It is taken orally and sometimes intravenously when used non-medically, and often combined with alcohol to achieve euphoria. Patients abusing the drug are also at risk of dependence. Withdrawal symptoms can be seen after long-term use of normal doses even after a gradual reduction regimen. The Compendium of Pharmaceuticals and Specialties recommends zopiclone prescriptions not exceed 7 to 10 days, owing to concerns of addiction, tolerance, and physical dependence. Two types of drug misuse can occur: either recreational misuse, wherein the drug is taken to achieve a high, or when the drug is continued long-term against medical advice. Zopiclone is as addictive as or may be more addictive than benzodiazepines. Those with a history of substance misuse or mental health disorders may be at an increased risk of high-dose zopiclone misuse. High-dose misuse of zopiclone and increasing popularity amongst people who use substances who have been prescribed with zopiclone was shown in the 1990s. The symptoms of zopiclone addiction can include depression, dysphoria, hopelessness, slow thoughts, social isolation, worrying, sexual anhedonia, and nervousness. Zopiclone and other sedative hypnotic drugs are detected frequently in cases of people suspected of driving under the influence of drugs. Other sedating drugs, including benzodiazepines and zolpidem, are also found in high numbers of suspected drugged drivers.
=== BLOSUM === BLOSUM80: more related proteins BLOSUM62: midrange BLOSUM45: distantly related proteins The BLOSUM62 matrix with the amino acids in the table grouped according to the chemistry of the side chain, as in (a). Each value in the matrix is calculated by dividing the frequency of occurrence of the amino acid pair in the BLOCKS database, clustered at the 62% level, divided by the probability that the same two amino acids might align by chance. The ratio is then converted to a logarithm and expressed as a log odds score, as for PAM. BLOSUM matrices are usually scaled in half-bit units. A score of zero indicates that the frequency with which a given two amino acids were found aligned in the database was as expected by chance, while a positive score indicates that the alignment was found more often than by chance, and negative score indicates that the alignment was found less often than by chance.
Sources: en.wikipedia.org
UHDTV potentially allows Rec. 2020, higher dynamic range, and higher frame rates to work on HD services without increasing resolution to 4K, providing improved quality without as high of an increase in bandwidth demand.
== Barotrauma in other animals == Whales and dolphins develop severely disabling barotrauma when exposed to excessive pressure changes induced by navy sonar, oil industry airguns, explosives, undersea earthquakes and volcanic eruptions. Injury and mortality of fish, marine mammals, including sea otters, seals, dolphins and whales, and birds by underwater explosions has been recorded in several studies. It has been claimed that bats can suffer fatal barotrauma in the low pressure zones behind the blades of wind turbines due to their more fragile mammalian lung structure in comparison with the more robust avian lungs, which are less affected by pressure change. The claims that have been made that bats can be killed by lung barotrauma when flying in low-pressure regions close to operating wind-turbine blades, have been supported by reports of measurements of the pressures around the turbine blades. The diagnosis and contribution of barotrauma to bat deaths near wind turbine blades have been disputed by other research comparing dead bats found near wind turbines with bats killed by impact with buildings in areas with no turbines.
Primary polycythemias are myeloproliferative diseases affecting red blood cell precursors in the bone marrow. Polycythemia vera (PCV) (a.k.a. polycythemia rubra vera (PRV)) occurs when excess red blood cells are produced as a result of an abnormality of the bone marrow. Often, excess white blood cells and platelets are also produced. A hallmark of polycythemia vera is an elevated hematocrit, with Hct > 55% seen in 83% of cases. A somatic (non-hereditary) mutation (V617F) in the JAK2 gene, also present in other myeloproliferative disorders, is found in 95% of cases. Symptoms include headaches and vertigo, and signs on physical examination include an abnormally enlarged spleen and/or liver. Studies suggest that mean arterial pressure (MAP) only increases when hematocrit levels are 20% over baseline. When hematocrit levels are lower than that percentage, the MAP decreases in response, which may be due, in part, to the increase in viscosity and the decrease in plasma layer width. Furthermore, affected individuals may have other associated conditions alongside high blood pressure, including formation of blood clots. Transformation to acute leukemia is rare. Phlebotomy is the mainstay of treatment. Primary familial polycythemia, also known as primary familial and congenital polycythemia (PFCP), exists as a benign hereditary condition, in contrast with the myeloproliferative changes associated with acquired PCV. In many families, PFCP is due to an autosomal dominant mutation in the EPOR erythropoietin receptor gene.
In biochemistry and metabolism, beta oxidation (also β-oxidation) is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA. The acetyl-CoA product of this step of fatty acid metabolism enters the citric acid cycle, generating NADH and FADH2, which are electron carriers used in the electron transport chain. It is named as such because the beta carbon of the fatty acid chain undergoes oxidation and is converted to a carbonyl group to start the cycle all over again. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although very long chain fatty acids are oxidized in peroxisomes. Beta oxidation occurs mainly in the heart, liver and kidney. The overall reaction for one cycle of beta oxidation is:
==== Declined ==== Grant Moody, Bexar County commissioner from the 3rd precinct Kyle Sinclair, former vice chair of the Bexar County Republican Party, candidate for the 28th district in 2024 and nominee for the 20th district in 2022 (ran in the 21st district)
Sources: en.wikipedia.org
== Causes == Pulmonary infection by bacteria, viruses and parasites Drugs: antineoplastic drugs, erlotinib, amiodarone Chemical exposure, most notably to diacetyl Vaping: On October 17, 2019, the American Journal of Clinical Pathology reported that lung biopsies from patients with vaping-associated pulmonary illness show acute lung injury patterns, including organizing pneumonia. Ionizing radiations Inflammatory diseases Systemic lupus Rheumatoid arthritis (RA-associated COP) Scleroderma Bronchial obstruction Proximal bronchial squamous cell carcinoma SARS-CoV-2 Analysis of COVID-19 CT imaging along with postmortem lung biopsies and autopsies suggest that the majority of patients with COVID-19 pulmonary involvement also have secondary organizing pneumonia (OP) or its histological variant, acute fibrinous and organizing pneumonia, which are both well-known complications of viral infections. It was identified in 1985, although its symptoms had been noted before but not recognised as a separate lung disease. The risk of COP is higher for people with inflammatory diseases like lupus, dermatomyositis, rheumatoid arthritis, and scleroderma. It most commonly presents in the 5th or 6th decade of life and it is exceedingly rare in children.
==== Negative electron-transfer dissociation ==== Fragmentation can also occur with a deprotonated species, in which an electron is transferred from the species to a cationic reagent in a negative electron transfer dissociation (NETD):
This may have caused or contributed to the extinction of the Pleistocene megafauna, although it is also possible that the late Pleistocene extinctions were (at least in part) caused by other factors such as disease and overhunting by humans. New research suggests that the extinction of the woolly mammoth may have been caused by the combined effect of climatic change and human hunting. Scientists suggest that climate change during the end of the Pleistocene caused the mammoths' habitat to shrink, resulting in a drop in population. The small populations were then hunted out by Paleolithic humans. The global warming that occurred during the end of the Pleistocene and the beginning of the Holocene may have made it easier for humans to reach mammoth habitats that were previously frozen and inaccessible. Small populations of woolly mammoths survived on isolated Arctic islands, Saint Paul Island and Wrangel Island, until c. 3700 BP and c. 1700 BP respectively. The Wrangel Island population became extinct around the same time the island was settled by prehistoric humans. There is no evidence of prehistoric human presence on Saint Paul island (though early human settlements dating as far back as 6500 BP were found on the nearby Aleutian Islands).
The British Phosphate Commissioners (BPC) was a board of Australian, British, and New Zealand representatives who managed extraction of phosphate from Christmas Island, Nauru, and Banaba (Ocean Island) from 1920 until 1981. Nauru was a mandate territory governed on behalf of Nauru by Australia, Britain and New Zealand. However, representatives on the Permanent Mandates Commission argued that the activities of the BPC on Nauru were exploitative and not to the benefit of Nauruans. Australia intentionally suppressed information about its activities in Nauru. In 1968, Nauru brought Australia up before the International Court of Justice over the environmental devastation that they had caused on Nauru.
=== Mechanism of action === Miconazole inhibits the fungal enzyme 14α-sterol demethylase, resulting in a reduced production of ergosterol. In addition to its antifungal actions, miconazole, similarly to ketoconazole, is known to act as an antagonist of the glucocorticoid receptor. Miconazole is also known to bind to tubulin and inhibit its polymerization. Miconazole inhibits CYP2J2.
Sources: en.wikipedia.org
It measures the amounts and identities of compounds in liquid samples by separation and detection. Depending on the detector and reference standards, results can be qualitative or quantitative. The technique is used in fields such as pharmaceutical analysis, food safety, and environmental monitoring.
Performance checks confirm that the chromatographic system works within preset limits before results are accepted. They examine factors such as peak resolution, tailing, and repeatability. If criteria fail, the run may need correction or repetition.
Retention time alone is not definitive proof because other compounds can elute at similar times. Confirmation usually uses a second method, a different column, or a detector such as mass spectrometry. Authentic standards strengthen identification.
Method validation is the documented process of showing that an HPLC procedure produces reliable results for a defined purpose. It examines parameters such as accuracy, precision, specificity, linearity, and robustness. Regulators and quality systems often require validation before routine use.