If you have been reading about Stationary 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.
Updated 2026-01-03. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| 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 |
Data handling and documentation are central to HPLC quality control. Electronic systems should have audit trails that record changes to methods, sequences, and results. Integration parameters, such as peak baseline and threshold, can affect reported areas and must be defined in advance. Out-of-specification results trigger a structured investigation that may include reanalysis, instrument checks, and review of sample preparation. Regulatory inspections often examine raw data, audit trails, and training records to verify that reported results are traceable and reliable.
Method validation establishes that an HPLC procedure is suitable for its intended use. Key parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Accuracy measures agreement with a true or accepted value, while precision describes repeatability and intermediate precision. Specificity confirms that the method measures the analyte without interference from impurities, degradants, or excipients. Validation is documented in a protocol and report, and acceptance criteria are set before experiments begin. Regulatory guidance varies by region, but the general principles are widely harmonized.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Common checks include retention time, peak area, resolution between critical pairs, tailing factor, and theoretical plate count. Results are compared with predefined limits, and a failed check requires investigation before sample results are reported. Quality control samples at low, middle, and high concentrations are injected at intervals to monitor accuracy and precision. Blank injections detect carryover and contamination, while control charts track performance over time.
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.
Trump stated that if he were elected, he would increase deportations, send the U.S. military to the border, expand U.S. Immigration and Customs Enforcement detentions through workplace raids, deputize local law enforcement to handle border security, increase U.S. Customs and Border Protection funding, as well as finish building the wall on the southern border. Trump has said he will deport both legal and illegal immigrants. The New York Times reported that Trump was considering "an extreme expansion of his first-term crackdown on immigration", such as "preparing to round up undocumented people already in the United States on a vast scale and detain them in sprawling camps while they wait to be expelled". Trump stated his intention to deport 11 million people through the construction of detention camps and deploy the military, relying on presidential wartime powers under the 18th-century Alien Enemies Act. Trump made false claims of a "migrant crime wave" that are not supported by data, and provided no evidence to back up his claims. In regards to his anti-immigrant nativism, Trump's tone grew harsher from his previous time as president, and used fearmongering, racial stereotypes, and more dehumanizing rhetoric when referring to illegal immigrants.
=== EC 1.3.7 With an iron–sulfur protein as acceptor === EC 1.3.7.1: 6-hydroxynicotinate reductase EC 1.3.7.2: 15,16-dihydrobiliverdin:ferredoxin oxidoreductase EC 1.3.7.3: phycoerythrobilin:ferredoxin oxidoreductase EC 1.3.7.4: phytochromobilin:ferredoxin oxidoreductase EC 1.3.7.5: phycocyanobilin:ferredoxin oxidoreductase EC 1.3.7.6: phycoerythrobilin synthase EC 1.3.7.7: ferredoxin:protochlorophyllide reductase (ATP-dependent) EC 1.3.7.8: benzoyl-CoA reductase EC 1.3.7.9: 4-hydroxybenzoyl-CoA reductase EC 1.3.7.10: pentalenolactone synthase EC 1.3.7.15: chlorophyllide a reductase
== Works == Simulated distillation of high-boiling petroleum fractions by capillary supercritical fluid chromatography and vacuum thermal gravimetric analysis, with Herbert E. Schwartz, Mieczyslaw M. Boduszynski, and Fu Su in Analytical Chemistry (journal), May 15, 1987
Later, Haseltine would go on to explain that regenerative medicine acknowledges the reality that most people, regardless of which illness they have or which treatment they require, simply want to be restored to normal health. Designed to be applied broadly, the original definition includes cell and stem cell therapies, gene therapy, tissue engineering, genomic medicine, personalized medicine, biomechanical prosthetics, recombinant proteins, and antibody treatments. It also includes more familiar chemical pharmacopeia—in short, any intervention that restores a person to normal health. In addition to functioning as shorthand for a wide range of technologies and treatments, the term "regenerative medicine" is also patient friendly. It solves the problem that confusing or intimidating language discourages patients. The term regenerative medicine is increasingly conflated with research on stem cell therapies. Some academic programs and departments retain the original broader definition while others use it to describe work on stem cell research. From 1995 to 1998 Michael D. West, PhD, organized and managed the research between Geron Corporation and its academic collaborators James Thomson at the University of Wisconsin–Madison and John Gearhart of Johns Hopkins University that led to the first isolation of human embryonic stem and human embryonic germ cells, respectively. In March 2000, Haseltine, Antony Atala, M.D., Michael D. West, Ph.D., and other leading researchers founded E-Biomed: The Journal of Regenerative Medicine.
Symptoms of estrogen overdosage may include nausea, vomiting, bloating, increased weight, water retention, breast tenderness, vaginal discharge, heavy legs, and leg cramps. These side effects can be diminished by reducing the estrogen dosage.
Sources: en.wikipedia.org
From 1935–1972, the authorising body governing radiation in Australia was the Commonwealth X-Ray and Radium Laboratory. This was replaced by the Commonwealth Radiation Laboratory (1972–1973), and then the Australian Radiation Laboratory (1973–1999). In 1999, the Australian Radiation Laboratory then merged with the Nuclear Safety Bureau to create one agency that governed radiation and nuclear safety, ARPANSA. Since its establishment, ARPANSA has offices in both Sydney, NSW, and Melbourne, Victoria.
Abortive initiation is a normal process of transcription and occurs both in vitro and in vivo. After each nucleotide-addition step in initial transcription, RNA polymerase, stochastically, can proceed on the pathway toward promoter escape (productive initiation) or can release the RNA product and revert to the RNA polymerase-promoter open complex (abortive initiation). During this early stage of transcription, RNA polymerase enters a phase during which dissociation of the transcription complex energetically competes with the elongation process. Abortive cycling is not caused by strong binding between the initiation complex and the promoter.
== Gameplay == The game involves two teams, Attackers and Defenders. Attackers win if they capture all the points on the map, defenders win if time runs out. After a round is over, the teams switch roles. If a player dies during a round, they will respawn after a few seconds.
== Selection == In order to ensure growth of only transformed bacteria (which carry the desired plasmids to be harvested), a marker gene is used in the destination vector for selection. Typical marker genes are for antibiotic resistance or nutrient biosynthesis. So, for example, the "marker gene" could be for resistance to the antibiotic ampicillin. If the bacteria that were supposed to pick up the desired plasmid had picked up the desired gene then they would also contain the "marker gene". Now the bacteria that picked up the plasmid would be able to grow in ampicillin whereas the bacteria that did not pick up the desired plasmid would still be vulnerable to destruction by the ampicillin. Therefore, successfully transformed bacteria would be "selected."
Starting in 2007, Jimmy John's began sponsoring NASCAR, first with Steven Wallace in 2007 and 2008. In 2009 and 2010, Jimmy John's sponsored Kevin Harvick in the NASCAR Nationwide Series. In 2011, Jimmy John's and Richard Childress Racing reached a multi-year agreement to sponsor Harvick for the Sprint Cup Series. The 2014 sponsorship continued with Harvick and the Stewart–Haas Racing team. On September 13, 2014, Jimmy John's became the title sponsor of the Jimmy John's Freaky Fast 300 at Chicagoland Speedway. Harvick won the 2014 NASCAR Sprint Cup Championship, giving Jimmy John's their first championship. From 2010 to 2019, Jimmy John's entered into an Ultimate Fighting Championship sponsorship with Brock Lesnar with logos appearing on his trunks. This sponsorship extended to WWE upon Lesnar's return to that company in 2012, making him the only WWE performer in history to be permitted such a deal. In 2015, Jimmy John's co-sponsored the RCH Factory Racing Supercross and Motocross team featuring Ken Roczen. The team contested both the Monster Energy AMA Supercross and the Lucas Oil Pro Motocross championships. In June, Jimmy John's sponsored former NASCAR champion Rusty Wallace for his Speed Energy Formula Off-Road debut at the 2015 X Games.
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.
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.