The short version of Chromatogram fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-01-26. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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.
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.
Large randomised controlled trials have shown that dapagliflozin significantly reduces worsening heart failure and heart failure hospitalisation across the spectrum of heart failure, including patients with reduced ejection fraction (LVEF <40%), mildly reduced ejection fraction (LVEF 41–49%) and preserved ejection fraction (LVEF ≥50%). Research shows that early initiation during hospitalization for acute heart failure appears safe in stable patients. Combined results of multiple trials also found that starting SGLT2 inhibitors in the hospital significantly lowers the risk of death from heart problems and prevents heart failure from getting worse. Dapagliflozin and other SGLT2 inhibitors may reduce hospitalisation for heart failure in Type 2 diabetic patients, with or without atherosclerotic cardiovascular disease,however evidence across these patient groups remains incomplete. Some meta-analyses and cohort studies have demonstrated consistent efficacy among SGLT2 inhibitors in reducing specific heart failure hospitalization, but there are no direct and definitive studies indicating the superiority of dapagliflozin over other SGLT2 inhibitors like empagliflozin and further studies are needed to support this claim In the European Union, dapagliflozin is indicated in adults for treatment of:
At sufficiently high doses, somnolence (sleepiness or drowsiness), confusion, syncope (loss of consciousness from fainting), shortness of breath, marked weakness, seizures, and coma may occur. Lethal nicotine poisoning rapidly produces seizures, and death – which may occur within minutes – is believed to be due to respiratory paralysis.
== External links == Allergies - Americal Academy of Allergy Asthma and Immunology Allergy Blood Testing - Lab Tests Online Radioallergosorbent+Test at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
inhibit secretion of many hormones, such as gastrin, cholecystokinin, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide, TSH, and vasoactive intestinal peptide, reduce secretion of fluids by the intestine and pancreas, reduce gastrointestinal motility and inhibit contraction of the gallbladder, inhibit the action of certain hormones from the anterior pituitary, cause vasoconstriction in the blood vessels, and reduce portal vessel pressures in bleeding varices. It has also been shown to produce analgesic effects, most probably acting as a partial agonist at the mu opioid receptor.
Sources: en.wikipedia.org
According to author Mark Cartwright, "Inca roads covered over 40,000 km (25,000 miles), principally in two main highways running north to south across the Inca Empire, which eventually spread over ancient Peru, Ecuador, Chile and Bolivia." Several sources challenge Cartwright's claim in stating that the Inca roads covered either more or less area then he describes. This number is difficult to solidify since some of the pathways of the Inca still may remain unaccounted for, being that they may have been washed away or covered by natural forces. "Inca engineers were also undaunted by geographical difficulties and built roads across ravines, rivers, deserts, and mountain passes up to 5,000 meters high." Many of the constructed roads are not uniform in design. Most of the uncovered roads are about one to four meters wide. Although this is true, some roads, such as the highway in Huanuco Pampa province, can be much larger. As mentioned in the Pathway systems section, the Inca people mainly traveled on foot. Knowing this, the roads created were most likely built and paved for both humans and animals to walk and/or run along. Several roads were paved with stones or cobbles and some were "edged and protected with the use of small stone walls, stone markers, wooden or cane posts, or piles of stones." Drainage was something that was of particular interest and importance to the Inca people. Drains and culverts were built to ensure that rainwater would effectively run off of the road's surface.
2 molecules of hydrogen + 1 molecule of oxygen = 2 molecules of water. The law of combining volumes of gases was announced publicly by Joseph Louis Gay-Lussac on the last day of 1808, and published in 1809. Since there was no direct evidence for Avogadro's molecular theory, very few chemists adopted Avogadro's hypothesis as generally valid until the Italian chemist Stanislao Cannizzaro argued convincingly for it during the First International Chemical Congress in 1860.
Involuntarily, I compare the mummified sovereign—now small and weathered—to the giant man I saw in 1886 entering the See of São Paulo. Amidst a colossal wave of people, he dominated the crowd, appearing many cubits taller. The body of Pedro II and that of his wife Teresa Cristina (who was also embalmed) were officially repatriated to Brazil aboard a Brazilian Navy ship in 1921. The emperor and empress are now interred in the Imperial Mausoleum within the Cathedral of Saint Peter of Alcantara in Petrópolis, a city founded by Pedro II himself.
==== Enzyme-linked immunosorbent assay ==== The enzyme-linked immunosorbent assay (ELISA) technique used for the analysis of YTXs is a recently developed method by Briggs et al. This competitive, indirect immunoassay uses polyclonal antibodies against YTX to determine its concentration in the sample. The assay is commercially available, and is a rapid technique for the analysis of YTXs in shellfish, algal cells, and culture samples. ELISA has several advantages: it is very sensitive, has a limit of quantification of 75 μg/kg, is relatively cheap, and is easy to carry out. The major disadvantage to this method is it cannot differentiate between the different YTX analogues and takes a long time to generate results.
=== Direct air capture === Anion exchange resins readily absorb CO2 when dry and release it again when exposed to moisture. This makes them one of the most promising materials for direct carbon capture from ambient air or direct air capture, as the moisture swing works to replace the more energy-intensive temperature swing or pressure swing used with other sorbents which then facilitates the desired outcome. A prototype demonstrating this process has been developed by Klaus Lackner at the Center for Negative Carbon Emissions.
Sources: en.wikipedia.org
coordination complex A chemical compound consisting of a central atom or ion, usually metallic and known as the coordination center, bonded to a surrounding array of other groups of atoms, e.g. molecules or ions, which are known as ligands or complexing agents. Many metal-containing compounds, especially those of the transition metals, are coordination complexes. See also complex.
27 May – A study published in Light: Science & Applications describes an additive-free, brine-discharge-free solar-thermal desalination method that uses femtosecond laser-etched superwicking black metal to produce fresh water from real ocean water while collecting nearly all remaining salts as solids. Tests using samples from the Pacific, Atlantic, and Indian Oceans show that the self-cleaning surface can prevent salt and mineral build-up, a major limitation of existing solar desalination systems. 31 May – A Phase 3 trial published in the New England Journal of Medicine reports that daraxonrasib, an investigational oral RAS(ON) inhibitor, nearly doubles median overall survival in patients with previously treated metastatic pancreatic cancer, from 6.6 months with standard chemotherapy to 13.2 months.
The practice of medicine in the United States is currently in a major transition. This transition is due to many factors, but primarily because of the implementation and integration of health technologies into healthcare. In recent years, the widespread adoption of electronic health records (EHR) has greatly impacted healthcare. In his book The Digital Doctor: Hope, Hype, and Harm at the Dawn of Medicine's Computer Age, Robert Wachter aims to inform readers about this transition. Wachter states that there will be fewer hospitals in the future, and due to the advancement of technologies, people will be more likely to go to hospitals for major surgeries or critical illness. In the future, nurse call buttons will not be needed in hospitals. Instead, robots will deliver medication, take care of patients, and administer the system. In addition, the electronic health record will look different. Healthcare providers will be able to enter the notes via speech-to-text transcriptions in real-time. Wachter stated that information will be edited collaboratively across the patient-care team to improve the quality. Also, natural language processing will be more developed to help parse out keywords. In the future, patient data will reside in the cloud, and patients as well as authorized providers and individuals will be able to access their data from any device or location. Big data analysis will constantly be improving. Artificial intelligence and machine learning will be constantly improving and developing as it receives new data.
Glycopeptides are peptides that contain carbohydrate moieties (glycans) covalently attached to the side chains of the amino acid residues that constitute the peptide. Over the past few decades it has been recognised that glycans on cell surface (attached to membrane proteins or lipids) and those bound to proteins (glycoproteins) play a critical role in biology. For example, these constructs have been shown to play important roles in fertilization, the immune system, brain development, the endocrine system, and inflammation. The synthesis of glycopeptides provides biological probes for researchers to elucidate glycan function in nature and products that have useful therapeutic and biotechnological applications.
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by regular behavior than other types of injuries. Of the 81 Tyrannosaurus foot bones examined in the study, one was found to have a stress fracture, while none of the 10 hand bones were found to have stress fractures. The researchers found tendon avulsions only among Tyrannosaurus and Allosaurus. An avulsion injury left a divot on the humerus of Sue the T. rex, apparently located at the origin of the deltoid or teres major muscles. The presence of avulsion injuries being limited to the forelimb and shoulder in both Tyrannosaurus and Allosaurus suggests that theropods may have had a musculature more complex than and functionally different from those of birds. The researchers concluded that Sue's tendon avulsion was probably obtained from struggling prey. The presence of stress fractures and tendon avulsions, in general, provides evidence for a "very active" predation-based diet rather than obligate scavenging. A 2009 study showed that smooth-edged holes in the skulls of several specimens might have been caused by Trichomonas-like parasites that commonly infect birds. According to the study, seriously infected individuals, including "Sue" and MOR 980 ("Peck's Rex"), might therefore have died from starvation after feeding became increasingly difficult.
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.