This is a working overview of stationary phase, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-03 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Abbreviation | HPLC | Also called high-performance liquid chromatography |
| Separation mechanism | Differential partitioning | Compounds distribute between mobile and stationary phases |
| Typical column chemistry | C18 (octadecylsilane) | Used in reversed-phase separations |
| Typical detector | UV-Vis or photodiode array | Mass spectrometry is common for trace and confirmatory work |
| Typical particle size | 1.8–5 µm | Smaller particles require higher pressure and can improve speed |
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.
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.
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.
== Farmed insects not used for protein == Many vegans avoid honey and silk because these require insect farming, even though the insects are not eaten. Silk production involves boiling silk worms alive in their cocoons. The red pigment carmine is produced from powdered bodies of scale insects, so some vegans avoid it. Shellac is produced from a resin secreted by the lac bug on specific trees in Asia. In addition to its use in industry, shellac is incorporated into some fruits, coffee beans, and candies as confectioner's glaze. Some vegans avoid confectioner's glaze because lac bugs may be killed during shellac production. Lac used to produce red dye may be even more injurious to lac bugs because while shellac comes from lac-bug secretions, lac dye's color comes from the insect bodies themselves. Insects are also farmed in large numbers for biological control, where large numbers of parasitic or predatory insects might be reared and then released into the wild to control a pest species. Alternately, in the sterile insect technique, large numbers of sterile male insects may be reared and released in order to reduce wild populations of pest insects or prevent their range expansion, such as with the screwworm. Finally, insects may play an unusual role in specific protein production: fruit flies can be used to generate recombinant proteins which can be used for the production of cell-cultured meat or across many other industries.
A systematic and independent examination of trial-related activities and documents to determine whether the evaluated trial-related activities were conducted, and the data were recorded, analyzed, and accurately reported according to the protocol, sponsor's standard operating procedures (SOPs), good clinical practice (GCP), and the applicable regulatory requirement(s). (ICH E6) Audit certificate
== Research == Antibodies and antigens, produced in the Human Protein Atlas workflow, are used in research projects to study potential biomarkers in various diseases, such as breast cancer, prostate cancer, colon cancer, diabetes, autoimmune diseases, ovarian cancer and renal failure. Researchers involved with Human Protein Atlas projects, are sharing protocols and method details in an open-access group on protocols.io. A large effort is put into validating the antibody reagents used for profiling of tissues and cells, and the HPA has implemented stringent antibody validation criteria as suggested by the International Working Group for Antibody Validation (IWGAV).
=== Criminal justice === Kennedy opposed the First Step Act, a bipartisan criminal justice reform bill. The bill passed 87–12 on December 18, 2018. Kennedy said the bill did not do enough to protect victims of crime, saying, "This is not a criminal justice bill. It is a prisoner release bill. We should be protecting victims of crimes and not the offenders who committed the crimes." In 2023, he introduced a bill that would lower the amount of fentanyl a dealer must possess to face the mandatory minimum prison sentence. Kennedy has criticized prosecutors for declining to prosecute some offenders. In 2023, he introduced the Prosecutors Need to Prosecute Act, which requires prosecutors to disclose when they decline to prosecute cases. It would also remove funding for prosecutors who fail to report such cases.
It was among the first such works to be published, and was followed by many books by white veterans of the war. The book has been widely cited, with historians and commentators arguing that it clearly illustrated the tactics used by the Rhodesians. It does not mention any of the atrocities committed by the Selous Scouts. Many other books have since been published about the Selous Scouts. These works often glorify the unit. In 2018 The New York Times reported that glorification of the Selous Scouts formed part of online nostalgia for Rhodesia and had been taken up by far-right movements that were sympathetic to the white Rhodesian regime. Items branded with the slogan and insignia of the Selous Scouts were available for sale, and a company called the "Selous Armory" was selling a range of apparel glorifying the Rhodesian military. In 2021, the newly established Ranger Regiment in the British Army adopted a cap badge that was similar in appearance to the Selous Scouts' and may have been based on it. The Telegraph reported that "numerous officers have raised concerns" over the badge. The British Army stated that the badge was "designed around the peregrine falcon" and not the osprey as used by the Rhodesian badge.
Sources: en.wikipedia.org
Microsomal glutathione S-transferase 3 is an enzyme that in humans is encoded by the MGST3 gene. The MAPEG (Membrane-Associated Proteins in Eicosanoid and Glutathione metabolism) family consists of six human proteins, several of which are involved the production of leukotrienes and prostaglandin E, important mediators of inflammation. This gene encodes an enzyme that catalyzes the conjugation of leukotriene A4 and reduced glutathione to produce leukotriene C4. This enzyme also demonstrates glutathione-dependent peroxidase activity towards lipid hydroperoxides.
== Further reading == Richardson, J. S. (1981). "The Anatomy and Taxonomy of Protein Structure". Anatomy and Taxonomy of Protein Structures. Advances in Protein Chemistry. Vol. 34. pp. 167–339. doi:10.1016/S0065-3233(08)60520-3. ISBN 978-0-12-034234-1. PMID 7020376., available on-line at Anatax Branden, C.-I.; Tooze, J. (1991), Introduction to Protein Structure, Garland Publishing, NY, ISBN 0-8153-0344-0 Arya, A (2026), Pearson Biochemistry: A Conceptual Approach, Pearson International, IN, ISBN 978-9-37-136081-4
Nando's opened its first restaurants within the United Kingdom, in 1992, in the west London suburbs of Ealing and Earls Court, initially focusing on takeaway food. The UK arm, owned by the Enthoven family via a private equity company, struggled until chairman Dick Enthoven put his son Robert in control. The focus then moved from takeaways to a mixed-service (counter ordering and table service) model. This decision was taken after Nando's partnered with Harrison, a branding and design agency. They also advised Nando's to design each restaurant individually so no two restaurants were the same, a brand characteristic of the chain. In 2013, the company employed around 8,000 staff in the UK and had over 280 branches, with about 60 serving food conforming with Islamic dietary laws. In 2010, Nando's UK won the Sunday Times's 'best place to work' award in the big company category. Its sauces and marinades were also retailed in UK supermarkets. Nando's claims to have the largest collection of South African art in the UK, with over 5,000 works displayed in restaurants; original artworks are commissioned by the company. In March 2020, all of Nando's UK restaurants closed temporarily due to nationwide lockdown rules introduced by the government to limit the spread of COVID-19. In late April 2020, Nando's reopened select locations for delivery and collection services, with many more locations opening throughout May. In early July 2020, the restaurant chain started reopening a few of its outlets for eat-in service.
Locals are called "Subordinate Assemblies"; the national "Supreme Assembly" meets quadrennially, board of directors runs things in between those. Headquarters in Philadelphia. Slovak Catholic Sokol - Founded in 1905 as the Roman and Greek Catholic Union; a gymnastic society much like Sokol USA, but with a stronger religious, Catholic emphasis, including financial assistance to missionaries and people preparing for the priesthood. Sponsors annual track and field event. In 1921 had 19,025 members, more than 42,000 in 1936, 44,243 in 1946, and 50,000 in 1979. 50,000 members in 1995. Headquarters in Passaic, New Jersey. Slogan: "Sound mind in a sound body in a sound society". Motto: Za boha a narod, "For God and Nation". Patron saint Martin of Tours. Had 25% million in assets in 1921; attended 26th International Eucharistic Congress; gives out 20 scholarships of $500 per year. Sokol U.S.A. - A Sokol movement, apparently popular among people of Czech and Slovak descent in the mid-19th century. The earliest antecedent of this particular organization was a lodge founded in 1896, full name Slovak Gymnastic Union Sokol of the United States of America. Sponsors gymnastic events called Slets, insurance benefits, dances and calisthenics, scholarships, and "camps and halls" in several states. 23,000 members in 1979, and 12,000 in 1995. Absorbed the Slovak Evangelical Society and the Tatran Slovak Union in 1944. United Lutheran Society - Traces its origins to the Slovak Evangelical Union founded in 1893 in Freeland, Pennsylvania. In 1906 the Evangelical Slovak Women's Union was founded.
Sources: en.wikipedia.org
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.
In most cases the sample is consumed or altered during analysis, though some detectors are non-destructive. Fractions can be collected after separation for further study. Repeated testing therefore requires additional sample.
Run times range from under a minute for fast methods to over an hour for complex separations. Sample preparation, equilibration, and data review add time. Throughput depends on instrument configuration and method requirements.
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.