If you have been reading about Mobile phase and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-12-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Separation mode | Reversed-phase | Most common for neutral and moderately polar analytes |
| Column particle size | 3–5 µm | Smaller particles improve resolution but raise backpressure |
| Mobile phase pH range | 2–8 | Silica-based columns may degrade outside this range |
| Typical flow rate | 1.0–2.0 mL/min | For analytical columns with 4.6 mm internal diameter |
| Common synonyms | HPLC, LC, high-pressure liquid chromatography | High-performance liquid chromatography is the standard expansion |
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.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Typical checks include retention time, peak area precision, resolution between critical pairs, tailing factor, and theoretical plate count. Acceptance criteria are set in the method or pharmacopeial monograph. If a suitability check fails, the run may be rejected and the instrument or sample preparation may need investigation. This practice helps prevent release of data from a system that has drifted out of control.
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.
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.
=== Odor problem === DMSO disposed into sewers can cause odor problems in municipal effluents: waste water bacteria transform DMSO under hypoxic (anoxic) conditions into dimethyl sulfide (DMS) that has a strong disagreeable odor, similar to rotten cabbage. However, chemically pure DMSO is odorless because of the lack of C-S-C (sulfide) and C-S-H (mercaptan) linkages. Deodorization of DMSO is achieved by removing the odorous impurities it contains.
=== Non-diabetics === In those with hypoglycemia who do not have diabetes, there are a number of preventative measures dependent on the cause. Hypoglycemia caused by hormonal dysfunction like lack of cortisol in Addison's disease or lack of growth hormone in hypopituitarism can be prevented with appropriate hormone replacement. The hypoglycemic episodes associated with non-B cell tumors can be decreased following surgical removal of the tumor, as well as following radiotherapy or chemotherapy to reduce the size of the tumor. In some cases, those with non-B cell tumors may have hormone therapy with growth hormone, glucocorticoid, or octreotide to also lessen hypoglycemic episodes. Post-gastric bypass hypoglycemia can be prevented by eating smaller, more frequent meals, avoiding sugar-filled foods, as well as medical treatment with an alpha-glucosidase inhibitor, diazoxide, or octreotide. Some causes of hypoglycemia require treatment of the underlying cause to best prevent hypoglycemia. This is the case for insulinomas which often require surgical removal of the tumor for hypoglycemia to remit. In patients who cannot undergo surgery for removal of the insulinoma, diazoxide or octreotide may be used.
== Reception == In 2015, Entertainment Weekly highlighted the scene where Kirk reads the United States Constitution, as one of the most important moments in that character's life. WhatCulture ranked this episode the 15th worst episode of the Star Trek franchise. In 2016, SyFy included this episode in a group of Star Trek franchise episodes they felt were commonly disliked but "deserved a second chance". In 2017, this episode was rated the 8th worst episode of the Star Trek franchise up to that time, by ScreenRant. In 2018, CBR included this episode on a ranking of episodes they stated were "So Bad They Must Be Seen". CBS News listed "The Omega Glory" as one of the worst episodes of the original series. In 2017, Den of Geek ranked this episode as the 5th worst Star Trek episode of the original series.
=== Recombinant human growth hormone (HGH, somatotropin) === Human growth hormone is administered to patients whose pituitary glands generate insufficient quantities to support normal growth and development. Before recombinant HGH became available, HGH for therapeutic use was obtained from pituitary glands of cadavers. This unsafe practice led to some patients developing Creutzfeldt–Jakob disease. Recombinant HGH eliminated this problem, and is now used therapeutically. It has also been misused as a performance-enhancing drug by athletes and others.
Much of his work, especially of the enzymes on aldolase and transaldolase was done in collaboration with Sandro Pontremoli at the University of Genoa. Horecker published many papers, of which Web of Science lists 450, many of them highly cited. The breadth of his work can be judged from papers on a wide variety of topics, such as galactose oxidase, metabolic formation of phosphglycerate, protein kinase-C, release of alkaline phosphatase from bacterial cells and prothymosin-α.
Sources: en.wikipedia.org
is the mean square radius of branched and linear macromolecules with identical molar masses. By utilizing MALS in conjunction with a concentration detector as described above, one create a log-log plot of the root-mean-square radius vs molar mass. The slope of this plot yields the branching ratio, g. In addition to branching, the log-log plot of size vs. molar mass indicates the shape or conformation of a macromolecule. An increase in the slope of the plot indicates a variation in conformation of a polymer from spherical to random coil to linear. Combining the mean-square radius from MALS with the hydrodynamic radius
mRNA display is a method to identify peptides which bind to a particular molecular target. The process utilizes two main components: an immobilized target and a peptide library in which each peptide is covalently linked to an mRNA:cDNA which encodes it. The immobilized target is mixed with the library in a binding step, then those peptide-mRNA:cDNA fusions which do not bind are washed away. The resulting mixture, which is enriched in peptide-mRNA:cDNA fusions that bind, is then amplified via a polymerase chain reaction (PCR). A new peptide library enriched in binding sequences is prepared from this cDNA, and the process is repeated for several rounds. The result is the isolation of nucleotides with sequences that encode peptides with high affinity for the target.
=== Cytokine storm === Prazosin has been shown to prevent death in animal models of cytokine storm. As a repurposed drug, prazosin is being investigated for the prevention of cytokine storm syndrome and complications of COVID-19 where it is thought to decrease cytokine dysregulation.
For each essential amino acid i, calculate Ai/Ri. Take the amino acid with the smallest value of Ai/Ri. Call it l. This is the limiting amino acid taking actual absorption into account. The DIAAS is 100% × Al/Rl. DIAAS provides three separate Ri reference profiles for different human age groups.
Global map of sulfur dioxide distribution United States Environmental Protection Agency Sulfur Dioxide page International Chemical Safety Card 0074 IARC Monographs. "Sulfur Dioxide and some Sulfites, Bisulfites and Metabisulfites". vol. 54. 1992. p. 131. NIOSH Pocket Guide to Chemical Hazards CDC – Sulfure Dioxide – NIOSH Workplace Safety and Health Topic Sulfur Dioxide, Molecule of the Month
Sources: en.wikipedia.org
A fusee is a practical necessity in watches using a verge escapement, and can also provide considerable benefit with a lever escapement and other high precision types of escapements (Hamiltons WWII era Model 21 chronometer used a fusee in combination with a detent escapement). Keywind watches are also commonly seen with conventional going barrels and other types of mainspring barrels, particularly in American watchmaking.
Pulse chase assays are an alternative method to cycloheximide chase assays and involve the radioactive labeling of newly translated proteins followed by a similar "chase" period. While this method is informative and provides the benefit of observing nascent protein abundance, the radioactive material it requires is expensive with a shorter shelf-life and demands more caution to use than cycloheximide. Disadvantages Some disadvantages to conducting cycloheximide chase assays include the toxic nature of cycloheximide. When used at high concentrations over a long period of time, cycloheximide will damage the DNA within the cell and impair critical cellular function. For this reason, cycloheximide chases do not typically last for more than 12 hours. This presents a limitation if the turnover of a particularly stable protein is being studied. Additionally, cycloheximide chases only offer the ability to look at steady state proteins levels as opposed to newly translated protein levels such as with pulse chase. Therefore, only protein degradation and not protein maturation is able to be observed.
AlphaKnot complements KnotProt, a database focused on experimentally determined protein structures and their topological features. KnotProt provides detailed descriptions of knots, slipknots, and related entanglements in experimentally characterized proteins, whereas AlphaKnot was developed primarily to examine the much larger population of structures generated by modern protein-structure prediction methods. AlphaKnot has been used to investigate the frequency and distribution of knots in protein families and to identify previously uncharacterized topological architectures. Large-scale analyses of AlphaFold structures have identified unusual knot types and proteins containing multiple knots, while comparison with experimentally determined structures has provided examples in which unusual predicted topologies were subsequently confirmed experimentally. The database can therefore be used both as a source of candidate knotted proteins for experimental investigation and as a computational tool for examining the relationship between protein sequence, structure, and topology.
=== Bone scan === The nuclear medicine technique commonly called the bone scan usually uses 99mTc. It is not to be confused with the "bone density scan", DEXA, which is a low-exposure X-ray test measuring bone density to look for osteoporosis and other diseases where bones lose mass without rebuilding activity. The nuclear medicine technique is sensitive to areas of unusual bone rebuilding activity, since the radiopharmaceutical is taken up by osteoblast cells which build bone. The technique therefore is sensitive to fractures and bone reaction to bone tumors, including metastases. For a bone scan, the patient is injected with a small amount of radioactive material, such as 700–1,100 MBq (19–30 mCi) of 99mTc-medronic acid and then scanned with a gamma camera. Medronic acid is a phosphate derivative which can exchange places with bone phosphate in regions of active bone growth, so anchoring the radioisotope to that specific region. To view small lesions (less than 1 centimetre (0.39 in)) especially in the spine, the SPECT imaging technique may be required, but in the United States most insurance companies require separate authorization for SPECT imaging.
Sources: en.wikipedia.org
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.
The pump maintains a steady flow rate and pressure, which keeps retention times reproducible. Pulsation or flow errors can shift peaks and distort quantitation. Modern pumps use feedback control to reduce these variations.
HPLC alone usually separates compounds but does not always identify them. Retention time matching with a known standard provides tentative identification. Coupling HPLC to mass spectrometry adds mass information that supports structural identification.
System suitability is a set of checks performed before and during an HPLC run to confirm that the instrument and method are working as expected. It may include retention time repeatability, resolution between peaks, peak symmetry, and signal intensity. Failing suitability criteria usually invalidates the run.