The short version of method validation fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-06-27. Anything still debated is marked as such rather than presented as settled.
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.
Documentation and traceability are central to regulated HPLC testing. Records typically include instrument logs, column history, mobile-phase preparation, sample preparation, injection sequences, raw chromatograms, and audit trails. Electronic systems may require user access controls, time-stamped changes, and backup procedures. Training records show that analysts are qualified for assigned methods. Audits and inspections check whether written procedures match actual practice and whether deviations are documented. These controls support reproducibility and allow results to be reconstructed if questions arise later.
Method validation establishes that an HPLC procedure is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, robustness, and solution stability. Accuracy reflects closeness to a reference value, while precision reflects agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from matrix components. Validation is documented through protocols and reports, and the required extent depends on the method's use and regulatory context.
Routine quality control uses system suitability, blank injections, check standards, and control samples to detect drift or contamination. System suitability criteria may specify minimum resolution, maximum tailing factor, and a permitted range for repeated injections. Blank injections reveal carryover or solvent contamination, while check standards confirm calibration accuracy over a batch. Control samples with known analyte levels can show whether results remain within statistical limits. When a control result falls outside limits, the analyst investigates the cause and may invalidate affected results before repeating the batch.
| Property | Value | Notes |
|---|---|---|
| Separation mode | Reversed-phase | Common for polar and moderately polar analytes |
| Typical column length | 100-250 mm | Shorter columns can reduce run time |
| Particle size | 3-5 micrometers | Smaller particles improve efficiency but raise pressure |
| Flow rate | 0.5-2.0 mL/min | Depends on column dimensions and pressure limits |
| Detection | UV-Vis absorbance | Widely used for compounds with chromophores |
Practical HPLC testing depends on careful sample preparation and instrument maintenance. Samples may require filtration, dilution, pH adjustment, or extraction to avoid column damage and matrix interference. Mobile phases are degassed and filtered, and columns are equilibrated before injection. Common problems include peak tailing, baseline drift, ghost peaks, carryover, and co-elution of analytes. Documentation of instrument logs, calibration records, and electronic audit trails supports data integrity and traceability. Ongoing training and routine maintenance help reduce variability between analysts and laboratories.
Quality control laboratories use HPLC to check identity, purity, concentration, and stability of raw materials and finished products. A validated method specifies the column, mobile phase, flow rate, detection wavelength, injection volume, and run time. Samples are prepared and compared against reference standards of known concentration. The resulting chromatogram provides quantitative data, such as assay values and impurity levels. This approach is common in pharmaceutical, food, environmental, and industrial testing where consistent measurements are required.
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.
Substances and classifications table (31/10/2008) – European Legal Database on Drugs Archived 2021-02-25 at the Wayback Machine Report on all substances controlled in at least one EU country in XLS format Designer Drug Compound List Archived 2017-11-07 at the Wayback Machine at Chemograph Plus, DigiLab Software GmbH "Fentanyl landscape | PiHKAL · info". isomerdesign.com.
==== Thylakoid composition ==== Embedded in the thylakoid membranes are important protein complexes which carry out the light reactions of photosynthesis. Photosystem II and photosystem I contain light-harvesting complexes with chlorophyll and carotenoids that absorb light energy and use it to energize electrons. Molecules in the thylakoid membrane use the energized electrons to pump hydrogen ions into the thylakoid space, decreasing the pH and turning it acidic. ATP synthase is a large protein complex that harnesses the concentration gradient of the hydrogen ions in the thylakoid space to generate ATP energy as the hydrogen ions flow back out into the stroma—much like a dam turbine. There are two types of thylakoids—granal thylakoids, which are arranged in grana, and stromal thylakoids, which are in contact with the stroma. Granal thylakoids are pancake-shaped circular disks about 300–600 nanometers in diameter. Stromal thylakoids are helicoid sheets that spiral around grana. The flat tops and bottoms of granal thylakoids contain only the relatively flat photosystem II protein complex. This allows them to stack tightly, forming grana with many layers of tightly appressed membrane, called granal membrane, increasing stability and surface area for light capture. In contrast, photosystem I and ATP synthase are large protein complexes which jut out into the stroma. They can't fit in the appressed granal membranes, and so are found in the stromal thylakoid membrane—the edges of the granal thylakoid disks and the stromal thylakoids.
Variola virus is large and brick-shaped and is approximately 330 nanometers by 260 nm, with a single linear double stranded DNA genome 186 kilobase pairs (kbp) in size and containing a hairpin loop at each end. It infects only humans in nature. Both enveloped and unenveloped virions are infectious. Infection with either the major or minor strain confers immunity against the other. Variola major, the more common of the two strains, caused the more clinically severe illness and accounted for the great majority of smallpox's historical mortality. The genome of variola major virus is about 186,000 base pairs in length. It is made from linear double stranded DNA and contains the coding sequence for about 200 genes. The center of the genome contains the majority of the essential viral genes, including for structural proteins, DNA replication, transcription, and mRNA synthesis. The ends of the genome vary more across strains and species of orthopoxviruses. These regions contain proteins that modulate the hosts' immune systems, and are primarily responsible for the variability in virulence across the orthopoxvirus family. Gene expression occurs entirely within the cytoplasm of the host cell, and follows a distinct progression during infection. About half of the viral genome is transcribed prior to the replication of viral DNA. The first set of expressed genes are transcribed by pre-existing viral machinery packaged within the infecting virion. These genes encode the factors necessary for viral DNA synthesis and for transcription of the next set of expressed genes.
Europe has a basic choice: either it lapses back into the old power politics and balance of power diplomacy of past centuries or it moves ahead along the road leading to a new order of peace and freedom, whether this be based on multinational or supranational cooperation. Our choice is clear: we are going forward.According to historian Sverre Bagge, a balance of power logic may have prevented unification of the three Scandinavian kingdoms (Norway, Sweden and Denmark), as balancing coalitions formed to prevent one kingdom from conquering the other kingdoms.
=== Location === Lower Saxony has a natural boundary in the north in the North Sea and the lower and middle reaches of the River Elbe, although parts of the city of Hamburg lie south of the Elbe. The state and city of Bremen is an enclave entirely surrounded by Lower Saxony. The Bremen/Oldenburg Metropolitan Region is a cooperative body for the enclave area. To the southeast, the state border runs through the Harz, low mountains that are part of the German Central Uplands. The northeast and west of the state, which form roughly three-quarters of its land area, belong to the North German Plain, while the south is in the Lower Saxon Hills, including the Weser Uplands, Leine Uplands, Schaumburg Land, Brunswick Land, Untereichsfeld, Elm, and Lappwald. In the northeast of Lower Saxony is the Lüneburg Heath. The heath is dominated by the poor, sandy soils of the geest, while in the central-east and southeast in the loess börde zone, productive soils with high natural fertility occur. Under these conditions—with loam and sand-containing soils—the land is well-developed agriculturally. In the west lie the County of Bentheim, Osnabrück Land, Emsland, Oldenburg Land, Ammerland, Oldenburg Münsterland, and on the coast East Frisia.
Sources: en.wikipedia.org
Banting House features archival materials, artifacts, and other ephemera associated with Banting as co-discoverer of insulin, doctor, and artist, as well as his involvement in the first and second world wars. One gallery depicts the kind of office Banting might have had, and contains several of his belongings, including his original medicine cabinet, and a graduated cylinder Banting used during his time at the University of Western Ontario. The apothecary in the next room features a sink that Banting installed for his medical practice. Other galleries in the museum hold original belongings of Banting as well, most notably his desk and his bed frame. The bed frame is kept in Banting's bedroom, and visitors are encouraged to take a moment or a picture with it, as it is not roped off like many other areas of the museum. Additionally, an official replica of the Nobel Prize medal co-awarded to Banting and Macleod is on display, as well as many of Banting's other medals. Other displays include the military gallery, which includes a representation of the type of operating room Banting would have worked in on the field during the First World War, some information on the projects he headed during the Second World War, and an entire gallery filled with artwork done by Banting.
Gas phase ion chemistry is a field of science encompassed within both chemistry and physics. It is the science that studies ions and molecules in the gas phase, most often enabled by some form of mass spectrometry. By far the most important applications for this science is in studying the thermodynamics and kinetics of reactions. For example, one application is in studying the thermodynamics of the solvation of ions. Ions with small solvation spheres of 1, 2, 3... solvent molecules can be studied in the gas phase and then extrapolated to bulk solution. Transition state theory is the theory of the rates of elementary reactions which assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated complexes. RRKM theory is used to compute simple estimates of the unimolecular ion decomposition reaction rates from a few characteristics of the potential energy surface.
The second approach of bioprinting is autonomous self-assembly. This approach relies on the physical process of embryonic organ development as a model to replicate the tissues of interest. When cells are in their early development, they create their own extracellular matrix building block, the proper cell signaling, and independent arrangement and patterning to provide the required biological functions and micro-architecture. Autonomous self-assembly demands specific information about the developmental techniques of the tissues and organs of the embryo. There is a "scaffold-free" model that uses self-assembling spheroids that subjects to fusion and cell arrangement to resemble evolving tissues. Autonomous self-assembly depends on the cell as the fundamental driver of histogenesis, guiding the building blocks, structural and functional properties of these tissues. It demands a deeper understanding of how embryonic tissues mechanisms develop as well as the microenvironment surrounded to create the bioprinted tissues.
Robert Guillaume (born Robert Peter Williams; November 30, 1927 – October 24, 2017) was an American actor and singer. He played Benson DuBois in the ABC television series Soap and its spin-off, Benson. He also voiced the mandrill Rafiki in The Lion King, and played Isaac Jaffe in Aaron Sorkin's dramedy Sports Night. In a career that spanned more than 50 years, Guillaume worked extensively on stage, television and film. He was nominated for a Tony Award for his portrayal of Nathan Detroit in Guys and Dolls, and twice won an Emmy Award for his portrayal of the character Benson DuBois, once in 1979 on Soap and again in 1985 on Benson. He also won a Grammy Award in 1995 for his spoken-word performance of an audiobook version of The Lion King. Guillaume was the first African-American actor to portray the title role in Andrew Lloyd Webber’s The Phantom of the Opera.
=== November === 1 November Amid an ongoing boom in artificial intelligence, the UK hosts the world's first international summit devoted to safely managing the technology. Computer simulations reveal that remnants of a protoplanet named Theia could be inside the Earth, left over from a giant collision in ancient times, which afterwards formed the Moon. Dinkinesh, previously thought to be a single asteroid, is revealed by NASA's Lucy probe to in fact be a binary pair. 5 November – A new record high efficiency of 33.9% is reported for a silicon-perovskite tandem solar cell. This also surpasses the Shockley-Quieser theoretical limit of 33.7% of single junction solar cells for the first time. 6 November – Scientists release the first connectome of neuropeptide signaling in an animal nervous system (C. elegans). On 1 November, a functional atlas of signal propagation in 23,433 pairs of neurons across the worm's head by direct optogenetic activation is published. On 17 November, the development of fluorescent neuropeptide sensors is reported. 7 November – A study finds that "catastrophic ecosystem collapse" of UK forests is likely within the next 50 years, due to a wide range of factors. 8 November – In 10 studies, researchers of the Sc2.0 project report yeast with a half-synthetic genome. 9 November – Surgeons report the first human eye transplant; the patient did not regain sight in the transplanted eye. 10 November – A new scalable technique for carbon nanotube-based MOSFETs is demonstrated.
Sources: en.wikipedia.org
It measures the amounts and identities of compounds in liquid samples by separation and detection. Depending on the detector and reference standards, results can be qualitative or quantitative. The technique is used in fields such as pharmaceutical analysis, food safety, and environmental monitoring.
Performance checks confirm that the chromatographic system works within preset limits before results are accepted. They examine factors such as peak resolution, tailing, and repeatability. If criteria fail, the run may need correction or repetition.
Retention time alone is not definitive proof because other compounds can elute at similar times. Confirmation usually uses a second method, a different column, or a detector such as mass spectrometry. Authentic standards strengthen identification.
Validation establishes suitability for a new method, while verification confirms that a method works in a specific laboratory. Verification is often used when a validated method is adopted with existing equipment and staff. Both rely on documented acceptance criteria.