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 2025-09-07. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Validation parameter | Accuracy | Closeness to a reference value. |
| Validation parameter | Precision | Repeatability or intermediate precision. |
| Validation parameter | Linearity | Proportional response across a range. |
| System suitability check | Resolution | Separation between adjacent peaks. |
| Quality control tool | Control chart | Tracks results over time for trends. |
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.
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.
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 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.
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.
Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the adrenal cortex to promote sodium retention by the kidneys. An oligopeptide, angiotensin is a hormone and a dipsogen. It is derived from the precursor molecule angiotensinogen, a serum globulin produced in the liver. Angiotensin was isolated in the late 1930s (first named "angiotonin" or "hypertensin", later renamed "angiotensin" as a consensus by the 2 groups that independently discovered it) and subsequently characterized and synthesized by groups at the Cleveland Clinic and Ciba laboratories.
with a similar structure in 2D. Thus the governing equation is an integro-differential equation similar to Coulomb's and Biot–Savart's law, not convenient for numerical computation. An equivalent weak or variational form of the equation, proved to produce the same velocity solution as the Navier–Stokes equation, is given by,
==== Quantities required ==== A rule of thumb for dry ice bath branding states that twenty pounds (9.1 kg) of dry ice and three US gallons (11 L) of 99% alcohol are sufficient to freeze-brand one hundred head of cattle inside a three to four-hour period. An entire day of freeze branding may consume 50–75 pounds (23–34 kilograms) of dry ice and six to nine US gallons (23 to 34 L) of ethanol. The dry ice should be broken up into egg-sized pieces, placed in a styrofoam container or styrofoam-insulated metal cooler and covered with at least three inches (7.6 cm) of alcohol. Many consumer coolers are made from plastics that become exceptionally brittle at cryogenic temperatures. This is a safety concern if heavy metal brands are frequently returned to coolant baths because 99% alcohol is extremely flammable. Insulated aluminum containers are preferred.
=== Education === Newsom joined Long Beach City College Superintendent Eloy Oakley in a November 2015 op-ed calling for the creation of the California College Promise, which would create partnerships between public schools, public universities, and employers and offer a free community college education. Throughout 2016, he joined Oakland mayor Libby Schaaf at the launch of the Oakland Promise and Second Lady Jill Biden and Los Angeles mayor Eric Garcetti at the launch of the LA Promise. In June 2016, Newsom helped secure $15 million in the state budget to support the creation of promise programs throughout the state. In December 2015, Newsom called on the University of California to reclassify computer science courses as a core academic class to incentivize more high schools to offer computer science curricula. He sponsored successful legislation signed by Governor Brown in September 2016, that began the planning process for expanding computer science education to all state students, beginning as early as kindergarten. In 2016, Newsom led an effort to enact a series of reforms at the University of California to give student-athletes additional academic and injury-related support, and to ensure that contracts for athletic directors and coaches emphasized academic progress. This came in response to several athletics programs, including the University of California–Berkeley's football team, which had the lowest graduation rates in the country.
Lightbearer: The second DLC story that follows Wellington Wells' local rock superstar, Nick Lightbearer (whose real name is Norbert Pickles). In this DLC, Nick does not use weapons to fend off his crazed fans; instead, Nick dispatches them by playing music on his electric guitar. Since there is no map available to guide him, he plays his guitar in front of the gilded full-body statues molded in his likeness to indicate his current destination. During a fan convention, Nick wakes one morning in his hotel room hallucinating a talking rat with the voice of his ex-agent Virgil. Nick's clothes are soaked in blood and he is unable to recall the events that led to his situation. Nick follows Virgil's advice and flees the hotel, returning to his old home which has been converted into a museum. After having a hallucinated battle with his ex-wife Petunia, Nick is instructed by Virgil to try and remember the events of last night. Nick realizes he wrote down a record of events in the form of lyrics, and plays them to his music to try and jog his memory. After experiencing a disturbing dream showing the real Virgil being murdered, Nick wakes up back in his hotel room as if nothing happened. He then heads down to the bar to try and make sense of everything, when he runs into Morrie Memento, a pianist he had fired from his band. Nick finds one of Morrie's songs familiar, and recovers his piano tuner in order to hear the full version.
Sources: en.wikipedia.org
Twenty of Bukele's governmental institutions were investigated by the office of the attorney general in November 2020 for corruption related to the COVID-19 pandemic, but the investigations were halted after the attorney general was removed by the Legislative Assembly on 1 May 2021. The United States has placed sanctions on several of Bukele's government officials, labeling them as corrupt. The officials include Javier Argueta (presidential advisor), Osiris Luna Meza (general director of penal centers), Carlos Marroquín Chica (chairman of the Social Fabric Reconstruction Unit), Martha Carolina Recinos (chief of the cabinet), Rogelio Rivas (former minister of justice), Ernesto Sanabria (press secretary), and Alejandro Zelaya (former minister of finance). The U.S. also considered some of Bukele's Legislative Assembly allies corrupt, including Guillermo Gallegos and Christian Guevara. Some of the individuals are included on the U.S. State Department's "Engel List" of Central American politicians and judges considered "corrupt and undemocratic". Bukele called the sanctions and labels "absurd". In May 2021, the United States diverted El Salvador funding from government institutions to civil society groups to combat perceived corruption in Bukele's government. On 11 November 2021, Bukele introduced the "Foreign Agents Law" to the Legislative Assembly with the goal of "prohibiting foreign interference" in Salvadoran political affairs.
Iraqi authorities announce that the US transferred the diplomatic and logistics hub at Baghdad International Airport to Iraq prior to the withdrawal of American soldiers from the country. Chinese leader Xi Jinping meets Trump at the White House during his first visit to Washington in a decade. The two leaders discuss trade, artificial intelligence, Taiwan and international conflicts, and agree to extend the existing US–China trade truce by two months. September 25 – Cities and states across the United States, including Lexington, Nashville, New Orleans, and Portland, hold commemorations honoring former American country singer Dolly Parton including the 9 to 5 song one month after her death. California becomes the first U.S. state to designate September 25 as Dolly Parton Day. September 26 A powerful nor'easter strikes the northeast United States. A New York City Housing Authority employee is killed by a falling tree in Brooklyn. Trump rejects Iran's seven-day ceasefire proposal over nuclear concerns. The Wall Street Journal reports that he privately expects U.S. bombing to resume after the midterm elections in November, although the scale remains undecided amid dwindling munitions stockpiles. September 27 – Trump says that he still expected more talks to resume with Iran during the week. Trump claims that Iran "wanted to make a deal," but they "overplayed their hand" by offering conditions that the US "would have maybe agreed to a year ago." September 28 SpaceX's Starship achieves orbit for the first time, and deploys 26 "next generation" Starlink V3 satellites.
{\displaystyle {\begin{array}{l}{}\\{\ce {^{238}_{92}U->[\alpha ][4.463\times 10^{9}\ {\ce {y}}]{^{234}_{90}Th}->[\beta ^{-}][24.11\ {\ce {d}}]{^{234\!m}_{91}Pa}}}{\begin{Bmatrix}{\ce {->[0.16\%][1.16\ {\ce {min}}]{^{234}_{91}Pa}->[\beta ^{-}][6.70\ {\ce {h}}]}}\\{\ce {->[99.84\%\ \beta ^{-}][1.16\ {\ce {min}}]}}\end{Bmatrix}}{\ce {^{234}_{92}U->[\alpha ][2.455\times 10^{5}\ {\ce {y}}]{^{230}_{90}Th}->[\alpha ][7.54\times 10^{4}\ {\ce {y}}]{^{226}_{88}Ra}->[\alpha ][1600\ {\ce {y}}]{^{222}_{86}Rn}}}\\{\ce {^{222}_{86}Rn->[\alpha ][3.8235\ {\ce {d}}]{^{218}_{84}Po}->[\alpha ][3.097\ {\ce {min}}]{^{214}_{82}Pb}->[\beta ^{-}][27.06\ {\ce {min}}]{^{214}_{83}Bi}->[\beta ^{-}][19.9\ {\ce {min}}]{^{214}_{84}Po}->[\alpha ][164.3\ \mu {\ce {s}}]{^{210}_{82}Pb}->[\beta ^{-}][22.2\ {\ce {y}}]{^{210}_{83}Bi}->[\beta ^{-}][5.012\ {\ce {d}}]{^{210}_{84}Po}->[\alpha ][138.376\ {\ce {d}}]{^{206}_{82}Pb}}}\end{array}}}
== GLP-1 and GIP receptor dual agonists == Tirzepatide is a dual agonist, targeting the GLP-1 and GIP receptors and given as a once-weekly injection. The FDA approved it for type 2 diabetes in May 2022. In the SURPASS-2 clinical trial, tirzepatide was compared directly against semaglutide, a GLP-1 mono-agonist, in nearly 1,900 adults with type 2 diabetes. Tirzepatide outperformed semaglutide at all doses in both reducing blood sugar and weight loss. At the highest dose, 60% of patients on tirzepatide achieved good blood sugar control and at least 10% weight loss, compared to only 22% of patients that did so on semaglutide. Side effects were mostly mild gastrointestinal symptoms, similar to other drugs in the GLP-1 class.
Sources: en.wikipedia.org
In many laboratories, hazards are present. Laboratory hazards might include poisons; infectious agents; flammable, explosive, or radioactive materials; moving machinery; extreme temperatures; lasers, strong magnetic fields or high voltage. Therefore, safety precautions are vitally important. Rules exist to minimize the individual's risk, and safety equipment is used to protect lab users from injury or to assist in responding to an emergency. The Occupational Safety and Health Administration (OSHA) in the United States, recognizing the unique characteristics of the laboratory workplace, has tailored a standard for occupational exposure to hazardous chemicals in laboratories. This standard is often referred to as the "Laboratory Standard". Under this standard, a laboratory is required to produce a Chemical Hygiene Plan (CHP) which addresses the specific hazards found in its location, and its approach to them. In determining the proper Chemical Hygiene Plan for a particular business or laboratory, it is necessary to understand the requirements of the standard, evaluation of the current safety, health and environmental practices and assessment of the hazards. Many schools and businesses employ safety, health, and environmental specialists, such as a Chemical Hygiene Officer to develop, manage, and evaluate their CHP. Additionally, third party review is also used to provide an objective "outside view" which provides a fresh look at areas and problems that may be taken for granted or overlooked due to habit.
=== Pharmacokinetics === In the in vitro studies, eluxadoline was found to be transported by OAT3 (SLC22A8), OATP1B1 (SLCO1B1), and BSEP (ABCB11) at the highest concentrations tested (400 ng/ml, which is 162-fold larger than the observed Cmax of the highest therapeutic dose of 100 mg). However, it was not to be transported by OCT1 POU2F1, OAT1 (organic anion transporter 1), OCT2, OATP1B3 (SLCO1B3), P-gp (P-glycoprotein), or BCRP (ABCG2). Multidrug resistance-associated protein 2 (MRP2)-vesicular accumulation of eluxadoline was observed, indicating that the drug is a substrate of MRP2. Eluxadoline was not found to inhibit BCRP-, BSEP-, MRP2-, OCT1-, OCT2-, OAT1-, OAT3-, or OATP1B3-mediated transport of probe substrates but inhibited the transport of probe substrates of OATP1B1 and P-gp. In the in vitro studies, it was observed that eluxadoline is an in vivo substrate of OATP1B1, OAT3, and MRP2. Finally, no inhibition or induction of cytochrome P450 enzymes was observed. Following a 100 mg dose of eluxadoline, the Cmax was about 2 to 4 ng/ml and AUC was 12 to 22 ng.h/ml. Eluxadoline has linear pharmacokinetics with no accumulation upon repeated twice daily dosing. Taking eluxadoline with high fat meal decreased the Cmax by 50% and AUC by 60%.
== Adverse effects == The most common adverse event reported in phase III trials for ripasudil was mild conjunctival hyperemia. Additionally, up to 3.8% of trial participants reported ocular irritation after using the drug with up to 5.7% reporting conjunctival hemorrhage. There were several cases of “abnormal sensation in the eye” reported. On a cellular level, Okumura et al. found that ripasudil produced "guttae-like" formations in ocular endothelial cells post-administration, which was attributed to, "protrusion formation along intracellular borders caused by the reduction in actomyosin contractility of the CECs." However, these morphological changes to the eye were considered transient and therefore quick to reverse, unlike symptoms Fuchs endothelial corneal dystrophy, a disorder for which these short-lived symptoms could be mistaken.
Sources: en.wikipedia.org
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.
System suitability is a set of checks run on the chromatographic system before sample analysis. It confirms that resolution, peak shape, retention time, and response meet predefined limits. Failure can invalidate the run and trigger corrective action.
Blank injections reveal peaks or baseline disturbances that come from solvents, reagents, or the instrument rather than the sample. They help distinguish contamination from actual analyte signals. Comparing blanks with sample runs supports accurate interpretation.
It measures the presence and amount of one or more compounds in a liquid sample. Separation occurs in a column, and detection produces a signal proportional to concentration. Identification usually requires comparison with a known reference standard under the same conditions.