HPLC comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-06-24. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample. A pump moves a liquid mobile phase through a column packed with a solid stationary phase. Compounds interact differently with both phases and travel at different rates, leaving the column at distinct retention times. A detector records these arrivals as peaks on a chromatogram. The resulting pattern supports identification and quantification of substances in mixtures. Modern instruments use high pressure to force solvent through small particles, which improves speed and resolution compared with older low-pressure liquid chromatography methods.
Separation in HPLC depends on the chemistry of the stationary phase, the composition of the mobile phase, and the physical properties of the column. Reverse-phase separations use a nonpolar stationary phase and a polar mobile phase, and they are common for many organic compounds. Ion-exchange, size-exclusion, and normal-phase modes serve other classes of analytes. Gradient elution changes solvent strength over time, while isocratic elution holds it constant. Flow rate, temperature, particle size, and column length all influence peak shape and resolution. Detection may use ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry, depending on the analyte and the required sensitivity.
| Property | Value | Notes |
|---|---|---|
| Validation parameter | Accuracy | Measured value compared with true or accepted value |
| Precision type | Repeatability | Same analyst, instrument, and short time interval |
| Linearity range | 50–150% of target concentration | Common for assay methods; method-dependent |
| Limit of quantitation | Signal-to-noise ratio of 10:1 | Lowest concentration with acceptable precision |
| Common synonyms | Method validation, analytical validation | Documented confirmation that a method is suitable |
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.
HPLC testing separates dissolved compounds by passing a liquid sample through a column packed with stationary phase. A pump delivers mobile phase at controlled flow, and the sample components interact differently with stationary and mobile phases. Compounds that spend more time in mobile phase elute earlier; those retained by stationary phase elute later. Detectors record elution as peaks, and peak area or height relates to amount. This mechanism underpins quantitative analysis of mixtures.
Most routine HPLC testing uses reversed-phase columns, where the stationary phase is nonpolar and the mobile phase is a polar mixture such as water with an organic solvent. Analytes partition between the two phases according to polarity, size, and charge. Gradients that change solvent composition over time can separate compounds with broad retention ranges. Isocratic conditions keep solvent composition constant and suit simpler mixtures. The choice of column chemistry, pH, and temperature affects selectivity and peak shape.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. UV detection is widely used because many organic compounds absorb light, but it requires a chromophore. Mass spectrometry provides mass-based identification and high sensitivity for trace analytes. Each detector has trade-offs in selectivity, cost, and compatibility with mobile phases. Quantification typically uses calibration curves prepared from reference standards. Results are reported as concentration, purity, or presence above a limit.
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.
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.
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.
=== NAADP inhibitors === Back in 2009, a selective cell-permeant NAADP antagonist, trans-Ned-19 was discovered which blocks Ca2+ signals and downstream Ca2+-dependent processes such as differentiation. Prior to that, only high concentrations of blockers of L-type Ca2+ channels (e.g. diltiazem, dihydropyridines) could be used (with obvious concerns over non-NAADP effects). A minor modification of Ned-19 produced another, more soluble antagonist, Ned-K. Although not true antagonism, the NAADP 'receptor' can self-inactivate when bound to non-releasing concentrations of NAADP itself. Such inactivating pre-pulses of NAADP were the first strategy for implicating NAADP in subsequent physiological pathways.
== Properties == Agarose is available as a white powder which dissolves in near-boiling water, and forms a gel when it cools. Agarose exhibits the phenomenon of thermal hysteresis in its liquid-to-gel transition, i.e. it gels and melts at different temperatures. The gelling and melting temperatures vary depending on the type of agarose. Standard agaroses derived from Gelidium has a gelling temperature of 34–38 °C (93–100 °F) and a melting temperature of 90–95 °C (194–203 °F), while those derived from Gracilaria, due to its higher methoxy substituents, has a gelling temperature of 40–52 °C (104–126 °F) and melting temperature of 85–90 °C (185–194 °F). The melting and gelling temperatures may be dependent on the concentration of the gel, particularly at low gel concentration of less than 1%. The gelling and melting temperatures are therefore given at a specified agarose concentration. Natural agarose contains uncharged methyl groups and the extent of methylation is directly proportional to the gelling temperature. Synthetic methylation however have the reverse effect, whereby increased methylation lowers the gelling temperature. A variety of chemically modified agaroses with different melting and gelling temperatures are available through chemical modifications. The agarose in the gel forms a meshwork that contains pores, and the size of the pores depends on the concentration of agarose added. On standing, the agarose gels are prone to syneresis (extrusion of water through the gel surface), but the process is slow enough to not interfere with the use of the gel.
2006: Chilean biochemist Cecilia Hidalgo Tapia became the first woman to receive the Chilean National Prize for Natural Sciences. 2006: Chinese-American biochemist Yizhi Jane Tao led a team of researchers to become the first to map the atomic structure of Influenza A, contributing to antiviral research. 2006: Parasitologist Susan Lim became the first Malaysian scientist elected to the International Commission on Zoological Nomenclature. 2006: Merieme Chadid became the first Moroccan person and the first female astronomer to travel to Antarctica, leading an international team of scientists in the installation of a major observatory in the South Pole. 2006: American computer scientist Frances E. Allen won the Turing Award for "pioneering contributions to the theory and practice of optimizing compiler techniques that laid the foundation for modern optimizing compilers and automatic parallel execution". She was the first woman to win the award. 2006: Israeli crystallographer Ada E. Yonath became the first woman awarded the Wolf Prize in Chemistry for "ingenious structural discoveries of the ribosomal machinery of peptide-bond formation and the light-driven primary processes in photosynthesis." 2006: Canadian-American computer scientist Maria Klawe became the president of Harvey Mudd College. 2007: Using satellite imagery, Egyptian geomorphologist Eman Ghoneim discovered traces of an 11,000-year-old mega lake in the Sahara Desert. The discovery shed light on the origins of the largest modern groundwater reservoir in the world.
Sources: en.wikipedia.org
Pharmacology is the science of drugs and medications, including a substance's origin, composition and interaction with biological systems; specifically through pharmacokinetics, pharmacodynamics, therapeutic use, and toxicology. The discipline examines these interactions through pharmacokinetics (what the body does to the drug) and pharmacodynamics (what the drug does to the body), both of which determine how a substance alters normal or abnormal biochemical function. Substances with medicinal properties are classified as pharmaceuticals, while the term drug encompasses any chemical agent that alters biological processes. Nanopharmacology is the specialization of pharmacology in the nanoscale. The field encompasses drug composition and properties, functions, sources, medicinal chemistry, drug design, molecular and cellular mechanisms, organ/systems mechanisms, signal transduction/cellular communication, molecular diagnostics, interactions, chemical biology, therapy, medical applications, toxicology, and antipathogenic capabilities. The two main areas of pharmacology are pharmacodynamics and pharmacokinetics. Pharmacodynamics studies the effects of a drug on biological systems, and pharmacokinetics studies the effects of biological systems on a drug. In broad terms, pharmacodynamics discusses the chemicals with biological receptors, and pharmacokinetics discusses the liberation, absorption, distribution, metabolism, and excretion (LADME) of chemicals from the biological systems. Pharmacology is not synonymous with pharmacy, though the two terms are frequently confused.
These cytosolic formyltransferase produce fMet-tRNAi, which can be used by cytosolic ribosomes to produce proteins with a N-terminal fMet. These proteins are targeted for degradation by specific processes in the cell.
== Treatment and Prognosis == There is very limited data on treatment and follow-up of smoking-related interstitial fibrosis. One study reported that corticosteroids were not beneficial. Smoking cessation resulted in stable/non-progressive disease after several years of follow-up. Improvements in pulmonary function tests with smoking cessation have also been documented.
== Notable people with Alport syndrome == Sam Clarke, British filmmaker Shae Hutchinson, Norwich City Football Club Under-23's player Christopher Kelsall, drummer for band Mirrortalk Ellie Kugler, American Kidney Fund ambassador and bodybuilder
Sources: en.wikipedia.org
On 1 August 2024, the EU Artificial Intelligence Act entered into force, establishing the first comprehensive EU-wide AI regulation. In 2024, the Council of Europe created the first international legally binding treaty on AI, called the "Framework Convention on Artificial Intelligence and Human Rights, Democracy and the Rule of Law". It was adopted by the European Union, the United States, the United Kingdom, and other signatories. In a 2022 Ipsos survey, attitudes towards AI varied greatly by country; 78% of Chinese citizens, but only 35% of Americans, agreed that "products and services using AI have more benefits than drawbacks". A 2023 Reuters/Ipsos poll found that 61% of Americans agree, and 22% disagree, that AI poses risks to humanity. In a 2023 Fox News poll, 35% of Americans thought it "very important", and an additional 41% thought it "somewhat important", for the federal government to regulate AI, versus 13% responding "not very important" and 8% responding "not at all important". A 2026 NBC News Decision Desk poll powered by SurveyMonkey found that 52% of American adults used AI tools very often or sometimes, but only 18% said they could trust AI-generated information most or almost all of the time, and 70% were more worried than excited about AI. Polls in the United States found the main public concerns were job losses, impersonation, misinformation and information privacy.
from the Miocene strata of the Santalla Formation (Spain), representing the first large vertebrate from the El Bierzo Basin reported to date. A study on deciduous teeth and juvenile skulls of members of the genus Chilotherium, providing evidence of utility of dental characters for species discrimination, is published by Kampouridis et al. (2026). Pandolfi, Codrea & Solomon (2026) describe fossil material of a member of the genus Acerorhinus from the Miocene strata from the Crețești 1 site (Romania), with greatest similarity to A. simplex, and refine the species content of the genus Acerorhinus. Titov et al. (2026) describe fossil material of Elasmotherium chaprovicum from the Pleistocene strata from the Taurida Cave (Crimea), including the first upper milk teeth of a member of the genus Elasmotherium reported to date. Ponomarev et al. (2026) report the discovery of fossil material of Stephanorhinus kirchbergensis in the Pleistocene strata from the Komi Republic (Russia), representing the northernmost record of the species in Europe reported to date. Uzunidis & Pandolfi (2026) report evidence of different dynamics of evolution of body mass of the narrow-nosed rhinoceros from Northern Europe and from the Mediterranean, as well as evidence of consistent mixed-feeding strategy in the studied species, with seasonal specialization toward either browsing or grazing in populations near the end of the temporal range of the species.
== Life and work == Emanuel Gil-Av was born 1916 in Pensa of Tzarist Russia. After the death of his father, a physician, the family moved first to Central Europe and in 1928 to Tel-Aviv, Israel, where Gil-Av attended High School. Gil-Av studied petroleum chemistry at the University of Strasbourg. In 1940 he escaped the German occupation to England where he worked at first in the chemical laboratory of Chaim Weizmann, followed by the Petrochemical Ltd. in Manchester. After World War II, he moved to Palestine and he joined the Daniel Sieff Institute in Rehovot which was later on to become the Weizmann Institute of Science. In 1951 he earned his PhD under the supervision of Ernst David Bergmann. In his study of oil shale deposits, Gil-Av developed complex-forming stationary phases employing silver(I) ions for selective olefin separations by gas chromatography (GC). In co-operation with the centre of peptide chemistry at the Weizmann Institute of Science, he developed methods of the gas-chromatographic resolution of racemic α-amino acids. By coating a glass capillary column with the chiral stationary phase (CSP) N-trifluoroacetyl-L-isoleucine lauryl ester, Gil-Av et al. carried out in 1966 the first gas-chromatographic enantioseparation of racemic amino acids as N-trifluoroacetyl-O-alkyl derivatives. Many racemic compounds, amenable for enantioselective interaction via hydrogen bonding with the CSP, could be analytically enantioseparated by GC.
Sources: en.wikipedia.org
System suitability is a set of checks that confirm the instrument and method perform within limits before sample analysis. It typically includes resolution, tailing factor, retention time, and peak area reproducibility. If a check fails, the run is invalidated until the cause is resolved.
QC samples are usually injected at the beginning, at intervals during the run, and at the end. The exact frequency depends on the method, sample count, and regulatory requirements. Results outside acceptance limits can require rejection of the affected samples and investigation.
Method validation demonstrates that an HPLC procedure produces reliable results for its intended purpose. It provides documented evidence for accuracy, precision, specificity, and other performance characteristics. Regulators and quality systems require validation before a method is used for release or stability testing.
HPLC testing measures the presence and amount of one or more compounds in a liquid sample. It separates mixture components and records detector responses as peaks, which are compared with reference standards. Results are usually reported as concentrations or relative percentages.