Everything below concerns precision. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-04-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| 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. |
Validation demonstrates that a method is suitable for its intended use. Typical performance characteristics include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Regulators and standards organizations provide frameworks, but specific requirements depend on the application and jurisdiction. System suitability tests are run before sample analysis to confirm resolution, peak symmetry, retention time repeatability, and sensitivity. A validated method is not permanently fixed; changes may require partial or full revalidation.
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.
To allocate funds, the NIH must first obtain its budget from Congress. This process begins with institute and center (IC) leaders collaborating with scientists to determine the most important and promising research areas within their fields. IC leaders discuss research areas with NIH management who then develops a budget request for continuing projects, new research proposals, and new initiatives from the Director. The NIH submits its budget request to the Department of Health and Human Services (HHS), and the HHS considers this request as a portion of its budget. Many adjustments and appeals occur between the NIH and HHS before the agency submits NIH's budget request to the Office of Management and Budget (OMB). OMB determines what amounts and research areas are approved for incorporation into the President's final budget. The President then sends the NIH's budget request to Congress in February for the next fiscal year's allocations. The House and Senate Appropriations Subcommittees deliberate and by fall, Congress usually appropriates funding. This process takes approximately 18 months before the NIH can allocate any actual funds. When a government shutdown occurs, the NIH continues to treat people who are already enrolled in clinical trials, but does not start any new clinical trials and does not admit new patients who are not already enrolled in a clinical trial, except for the most critically ill, as determined by the NIH Director.
Ions can be created in an inductively coupled plasma, which is a plasma source in which the energy is supplied by electrical currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.
== Pipeline drugs == Lucitanib is a tyrosine kinase activity inhibitor, highly selective for VEGFR types 1-3, FGFR types 1-2 and PDGFR alpha/beta. Tumor types such as breast carcinoma show amplification of fibroblast growth factor related genes. Simultaneous inhibition of VEGF and FGF receptors in FGFR1 dependent tumors could be therapeutically advantageous. Lucitanib has been shown to have promising efficacy, a manageable side-effect profile and clinical benefits in both FGF-aberrant and angiogenesis-sensitive populations leading to a phase II program being planned. Motesanib is a small-molecule multikinase inhibitor highly selective for VEGFR 1-3, PDGFR and KIT. The drug has shown anti-tumor activity as a monotherapy in advanced solid tumors. Vatalanib is an antiangiogenic VEGFR inhibiting molecule which is being researched as a potential treatment of solid tumors. Vatalanib inhibits VEGFR 1-4 although it has greater potency as an inhibitor of VEGFR 1-2. At concentrations under 10 μM, Vatalanib does not have cytotoxic or antiproliferative effects on cells that do not express VEGF. Specific inhibition of tumor-induced angiogenesis like the inhibition by Vatalanib can both prevent ongoing growth of tumors and the metastatic potential. Cediranib is a multi VEGFR 1-3 inhibitor being tested as a maintenance treatment for patients with platinum sensitive relapsed ovarian cancer. Cediranib stops blood flow to the site of the tumour and thereby inhibits its growth.
Sources: en.wikipedia.org
Since the RCL is still covalently attached to the protease via the ester bond, the S to R transition pulls protease from the top to the bottom of the serpin and distorts the catalytic triad. The distorted protease can only hydrolyse the acyl enzyme intermediate extremely slowly and so the protease remains covalently attached for days to weeks. Serpins are classed as irreversible inhibitors and as suicide inhibitors since each serpin protein permanently inactivates a single protease, and can only function once.
== Mobile phase == The mobile phase is composed primarily of supercritical carbon dioxide, but since CO2 on its own is too non-polar to effectively elute many analytes, cosolvents are added to modify the mobile phase polarity. Cosolvents are typically simple alcohols like methanol, ethanol, or isopropyl alcohol. Other solvents such as acetonitrile, chloroform, or ethyl acetate can be used as modifiers. For food-grade materials, the selected cosolvent is often ethanol or ethyl acetate, both of which are generally recognized as safe (GRAS). The solvent limitations are system and column based.
=== Genomics === Notable P. fluorescens strains SBW25, Pf-5 and PfO-1 have been sequenced, among others. A comparative genomic study (in 2020) analyzed 494 complete genomes from the entire Pseudomonas genus, with 25 of them being annotated as P. fluorescens. The phylogenomic analysis clearly showed that the 25 strains annotated as P. fluorescens did not form a monophyletic group. In addition, their Average Nucleotide Identities did not fulfil the criteria of a species, since they were very diverse. It was concluded that P. fluorescens is not a species in the strict sense, but should be considered as a wider evolutionary group, or a species complex, that includes within it other species too. This finding is in accordance with previous analyses of 107 Pseudomonas species, using four core 'housekeeping' genes, that consider P. fluorescens as a relaxed species complex. The P. fluorescens relaxed evolutionary group that was defined by Nikolaidis et al. on the basis of the genus phylogenomic tree, comprised 96 genomes and displayed high levels of phylogenetic heterogeneity. It comprised many species, such as Pseudomonas corrugata, Pseudomonas brassicacearum, Pseudomonas frederiksbergensis, Pseudomonas mandelii, Pseudomonas kribbensis, Pseudomonas koreensis, Pseudomonas mucidolens, Pseudomonas veronii, Pseudomonas antarctica, Pseudomonas azotoformans, Pseudomonas trivialis, Pseudomonas lurida, Pseudomonas poae, Pseudomonas libanensis, Pseudomonas synxantha, and Pseudomonas orientalis. The core proteome of the P. fluorescens group comprised 1396 proteins.
Hyperinsulinemia is a condition in which there are excess levels of insulin circulating in the blood relative to the level of glucose. While it is often mistaken for diabetes or hyperglycaemia, hyperinsulinemia can result from a variety of metabolic diseases and conditions, as well as non-nutritive sugars in the diet. While hyperinsulinemia is often seen in people with early stage type 2 diabetes mellitus, it is not the cause of the condition and is only one symptom of the disease (for opposing view see review in ). Type 1 diabetes only occurs when pancreatic beta-cell function is impaired. Hyperinsulinemia can be seen in a variety of conditions including diabetes mellitus type 2, in neonates and in drug-induced hyperinsulinemia. It can also occur in congenital hyperinsulinism, including nesidioblastosis. Hyperinsulinemia is associated with hypertension, obesity, dyslipidemia, insulin resistance, and glucose intolerance. These conditions are collectively known as metabolic syndrome. This close association between hyperinsulinemia and conditions of metabolic syndrome suggest related or common mechanisms of pathogenicity. Hyperinsulinemia has been shown to "play a role in obese hypertension by increasing renal sodium retention". In type 2 diabetes, the cells of the body become resistant to the effects of insulin as the receptors which bind to the hormone become less sensitive to insulin concentrations resulting in hyperinsulinemia and disturbances in insulin release.
Sources: en.wikipedia.org
=== Advocacy groups === Even the Score, a coalition of women's groups brought together by a Sprout consultant, actively campaigned for the approval of flibanserin. The campaign emphasized that several approved treatments for male sexual dysfunction exist, while no such treatment for women was available. The group successfully obtained letters of support from the President of the National Organization for Women, the editor of the Journal of Sexual Medicine, and several members of Congress. Other organizations supporting the approval of flibanserin included the National Council of Women's Organizations, the Black Women's Health Imperative, the Association of Reproductive Health Professionals, National Consumers League, and the American Sexual Health Association. The approval was opposed by the National Women's Health Network, the National Center for Health Research and Our Bodies Ourselves. A representative of PharmedOut said "To approve this drug will set the worst kind of precedent—that companies that spend enough money can force the FDA to approve useless or dangerous drugs." An editorial in JAMA noted that, "Although flibanserin is not the first product to be supported by a consumer advocacy group in turn supported by pharmaceutical manufacturers, claims of gender bias regarding the FDA's regulation have been particularly noteworthy, as have the extent of advocacy efforts ranging from social media campaigns to letters from members of Congress".
The scientific name Asteroidea was given to starfish by the French zoologist de Blainville in 1830. It is derived from the Greek aster, ἀστήρ (a star) and the Greek eidos, εἶδος (form, likeness, appearance). Starfish are included in the subphylum Asterozoa along with brittle and basket stars (order Ophiuroidea), the characteristics of which include a star-shaped body as adults, with multiple arms surrounding central disc. The arms of asteroids are skeletally connected to the disc by ossicles in the body wall while ophiuroids have clearly demarcated arms. The starfish are a large and diverse class with over 1,900 living species. There are seven extant orders: Brisingida, Forcipulatida, Notomyotida, Paxillosida, Spinulosida, Valvatida and Velatida. Living asteroids, the Neoasteroidea, are distinct from their forerunners in the Paleozoic. Their classification has changed little but there is debate in regards to Paxillosida. The deep-water sea daisies, though clearly Asteroidea and currently included in Velatida, do not fit easily in any accepted lineage. Phylogenetic data suggests that they may be a sister group, the Concentricycloidea, to the Neoasteroidea, or that the Velatida themselves may be a sister group.
== Related heterocycles == Benzimidazole, an analog with a fused benzene ring Dihydroimidazole or imidazoline, an analog where the 4,5-double bond is saturated Pyrrole, an analog with only one nitrogen atom in position 1 Oxazole, an analog with the nitrogen atom in position 1 replaced by oxygen Thiazole, an analog with the nitrogen atom in position 1 replaced by sulfur Pyrazole, an analog with two adjacent nitrogen atoms Triazoles, analogs with three nitrogen atoms
== Other animals == Animal models of androgenic alopecia occur naturally and have been developed in transgenic mice; chimpanzees (Pan troglodytes); bald uakaris (Cacajao rubicundus); and stump-tailed macaques (Macaca speciosa and M. arctoides). Of these, macaques have demonstrated the greatest incidence and most prominent degrees of hair loss. Baldness is not a trait unique to human beings. One possible case study is about a maneless male lion in the Tsavo area. The Tsavo lion prides are unique in that they frequently have only a single male lion with usually seven or eight adult females, as opposed to four females in other lion prides. Male lions may have heightened levels of testosterone, which could explain their reputation for aggression and dominance, indicating that lack of mane may at one time have had an alpha correlation. Although nonhuman primates do not go bald, their hairlines do undergo recession. In infancy, the hairline starts at the top of the supraorbital ridge, but slowly recedes after puberty to create the appearance of a small forehead.
More recently, it has become much more commonplace to use ethyl chloroformate instead of cyanogen bromide for the Von Braun degradation demethylation step. See for example the list of phenyltropanes or the synthesis of paroxetine for further examples of this.
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.
HPLC testing separates and quantifies components in a liquid sample. It is used to check identity, purity, concentration, or stability. The technique works best for compounds that dissolve and are not easily vaporized.