This is a working overview of quality control, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-08-27. Anything still debated is marked as such rather than presented as settled.
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.
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.
| 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 |
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.
Developing an HPLC test begins with defining the analytes, matrix, and required reporting limits. Chemists select a separation mode, column chemistry, mobile phase composition, flow rate, and detection wavelength or mass transition. Experiments then adjust these variables to achieve adequate retention, resolution, and peak shape. System suitability tests confirm that the instrument and method perform consistently before sample analysis. Without suitable resolution, quantitative results may be unreliable. Preliminary runs often use scouting gradients to locate retention windows.
Validation establishes that a method is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, robustness, and stability of standards and samples. Acceptance criteria are defined in advance, and results are documented in a validation report. Regulatory guidance for pharmaceuticals, foods, and environmental testing differs, so the applicable framework must be identified. Ongoing verification uses control samples and trend charts after validation. Method transfer to another laboratory may require partial revalidation.
Routine quality control includes blanks, duplicates, spiked samples, and certified reference materials. Calibration curves are prepared with standards at several concentrations, and the detector response is checked for linearity. Carryover, column aging, mobile phase evaporation, and temperature drift can shift retention times or peak areas. Maintenance such as replacing seals, filters, and columns helps prevent failures. Records of injections, integration, and deviations support traceability. Audits may request raw data and instrument logs for each batch.
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.
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.
εl/w = (D/H)l/(D/H)w−1 = [(δDl + 1)/(δDw + 1)]−1; where εl/w = net or apparent fractionation, δDl = lipid product and δDw = source water. The δDs of common lipid classes found in living organisms are: n-alkyl: −170‰ ± 50‰ (113‰–262‰ more D-depleted than growth water) isoprenoid: −270‰ ± 75‰ (142‰–376‰ more D-depleted than growth water) phytol: −360‰ ± 50‰ (more depleted than the other two categories) Polyisoprenoid lipids are more depleted than acetogenic (n-alkyl) lipids with more negative δDs.
Overcoming serious difficulties, President Suárez achieved these two objectives and the first free elections since 1936 could be held on June 15, 1977. Union of the Democratic Centre (UCD), the party organized by President Suárez, won the elections, although not by absolute majority, and sought the consensus of the rest of the political forces ─ and especially of the other great winner, the PSOE ─ to create the new legal framework that was to replace the fundamental laws of the Franco regime, as well as to face the economic crisis, the reappearance of the "regional question" and the increase of terrorism by ETA. This led to the creation of the political transition to democracy model, which was based on the Amnesty Law of 1977 that included everything that had happened during the Franco dictatorship ─ thus constituting a so-called "pact of oblivion" ─ and in the approval of a Consensus Constitution in exchange for the leftist parties abandoning their claim to establish the Republic. On December 6, 1978, the referendum was held and the new democratic Constitution was approved. Once the Constitution was endorsed, President Suárez called elections for March 1979, which were won by UCD but again without an absolute majority. During the following two years, the governing party suffered an acute process of internal decomposition that culminated with the resignation of Adolfo Suárez in January 1981.
The cell counters of that time used LED screens for result review. In 1982, Medonic AB, another Swedish company with focus on hematology, was founded. The founders, Ingemar Berndtsson and Abraham Bottema, both had a long history and experience in hematology, clinical chemistry, and blood banking engineering. In 1985, Medonic AB launched the Cellanalyzer CA 480 system, its first own-developed cell counter with a built-in display that also showed the cell histograms. When computers began to be incorporated into the analyzers, other brands, like the Swelab analyzers, also came with a display. Both targeting the smaller clinical laboratories, Swelab Instrument AB and Medonic AB were competitors on the decentralized hematology testing market. In the late 90s, both Swelab Instrument AB and Medonic AB were acquired by Boule Diagnostics AB. The company has kept the parallel brands and the analyzers are still manufactured from its facilities in Stockholm, Sweden and supplied under the Swelab and Medonic trademarks for the decentralized hematology testing market. When Coulter was acquired by Beckman, former Coulter employees Dr. Harold R Crews, Andrew C Swanson, and Donald Grantham founded Clinical Diagnostic Solutions, Inc. (CDS) in 1997, focusing on the development and production of generic reagents and control material. In 2004, CDS was acquired by Boule. By this acquisition, Boule came to master the skills of the development and production of both instruments and the consumables included in a complete hematology system.
Sources: en.wikipedia.org
Instant coffee is sold in powder or granulated form in glass or plastic jars, sachets, or tins. Hot water, or sometimes milk or cold water (for iced coffee such as Greek frappé), is added to it, with milk and sugar if desired, to make a beverage. Strength is controlled by the ratio of coffee powder to liquid. In some countries, including Portugal, Spain, and India, instant coffee is commonly mixed with hot milk instead of water. Instant coffee is also sold pre-mixed with non-dairy creamer and sugar; this is popular in South Korea, termed "coffee mix".
The state prosecuted the accused as Marxist revolutionaries seeking to establish a Soviet-backed regime in South West Africa. In what became known as the "1967 Terrorist Trial", six of the accused were found guilty of committing violence in the act of insurrection, with the remainder convicted for armed intimidation, or having received military training for the purpose of insurrection. During the trial, the defendants unsuccessfully argued against allegations that they were privy to an external communist plot. All but three received sentences ranging from five years to life imprisonment on Robben Island.
=== Dynamic catch === The above bonds involve bimolecular interactions, which arguably represents the simplest types. A new type of catch bonds emerges when trimolecular interactions are involved. In such cases, one molecule can interact with the two counter-molecules using two binding sites, either separately, i.e. one at a time in the absence of the other to form bimolecular bonds, or concurrently to form a trimolecular bond when both counter-molecules are present. An interesting finding is that even when the two bimolecular interactions behave as slip bonds, the trimolecular interaction can behave as catch bond. This new type of catch bond, which requires concurrent and cooperative binding, is termed dynamic catch.
=== Exoenzymes === Exoenzymes are enzymes secreted by microorganisms, such as bacteria and fungi, to function outside their cells. These enzymes are crucial for breaking down large molecules in the environment into smaller ones that the microorganisms can absorb (transport into their cells) and use for growth and energy. Several studies have demonstrated that the activity of extracellular enzymes in aquatic microbial ecology is of algal origin. These exoenzymes released from microalgae include alkaline phosphatases, chitinases, β-d-glucosidases, proteases etc. and can influence the growth of microorganisms, chemical signaling, and biogeochemical cycling in ecosystems. The study of these exoenzymes may help to optimize the nutrient supplement strategy in aquaculture. Nevertheless, only a few of the enzymes were isolated and purified. Selected prominent enzyme classes are highlighted in the cited literature.
Sources: en.wikipedia.org
Actinides seem to be a little less hard than lanthanides, probably due to a longer spatial extent of 5f atomic orbitals with respect to 4f ones, then a selective separation is possible thanks to ligands bearing soft donors such as nitrogen and sulfur atoms, by a different bonding nature compared to hard donors. Despite the potential separation of actinides, a direct extraction from the PUREX raffinate is very hard, due to the presence of many other interfering species in the feed such as activation and fission products. In this perspective, advanced separation processes involving very selective extracting agents are required to achieve an efficient partitioning for the following transmutation process. To sum up, knowledge of hydration, acid-base interactions, kinetics and thermodynamic stabilities and speciation of actinide and lanthanide ions with ligands is of great value to understand a solvent extraction process and to design new and promising extracting agents.
=== Disputes with other politicians === In October 2023, Ford publicly stated that MPP Sarah Jama had a "long and well-documented history of antisemitism" and "hateful views", and that she "publicly support[ed] the rape and murder of innocent Jewish people," and called for her to resign. In response, Jama served Ford's office a cease and desist letter and threatened to sue him for libel. In April 2024, Doug Ford called for the reversal of the Speaker's ban on wearing keffiyeh in the legislature, which was imposed after an unidentified MPP complained about Sarah Jama donning a Palestinian keffiyeh at the start of the Gaza war. The motion to overrule the ban did not receive unanimous consent and remained in effect. In August 2026, it was reported that Ford's Progressive Conservative Party had sent a party official to follow Ontario Liberal Party leader Bonnie Crombie while she vacationed in Jamaica shortly after her election in 2023.
== Treatment == Recommendations to treat pressure ulcers include the use of bed rest, pressure redistributing support surfaces, nutritional support, repositioning, wound care (e.g., debridement, wound dressings) and biophysical agents (e.g., electrical stimulation). Reliable scientific evidence to support the use of many of these interventions, though, is lacking. More research is needed to assess how to best support the treatment of pressure ulcers, for example by repositioning.
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.
System suitability is a set of checks performed before and during an HPLC run to confirm that the instrument and method are working as expected. It may include retention time repeatability, resolution between peaks, peak symmetry, and signal intensity. Failing suitability criteria usually invalidates the run.