Resolution 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.
Last reviewed on 2026-06-19. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Primary guidance | ICH Q2(R2) | Analytical procedure validation |
| Compendial chapter | USP <621> | Chromatography general chapter |
| Validation parameter | Accuracy | Closeness to accepted true value |
| System suitability check | Peak resolution | Ensures separation between adjacent peaks |
| Data record | Audit trail | Supports data integrity and traceability |
Several separation modes exist, including reversed-phase, normal-phase, ion-exchange, size-exclusion, and hydrophilic interaction liquid chromatography. Reversed-phase uses a nonpolar stationary phase with a polar mobile phase and is widely applied to small organic molecules. Gradient elution changes mobile phase composition during the run, while isocratic elution keeps it constant. Column chemistry, particle size, temperature, flow rate, and mobile phase pH all influence retention and resolution. Method development selects conditions that separate analytes from matrix components and from each other.
Detection commonly uses ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. Ultraviolet detection depends on molecular chromophores that absorb light at specific wavelengths. Mass spectrometry provides mass information and sensitive quantification, often after electrospray ionization. Before sample batches, performance checks examine resolution, elution time repeatability, peak symmetry, and plate count. Matrix effects and co-elution remain recognized uncertainties; formal validation studies and orthogonal detection help address them. Detector choice depends on analyte properties and required sensitivity.
High-performance liquid chromatography, or HPLC, separates dissolved compounds by passing a liquid mobile phase through a packed column. Components distribute differently between the stationary phase and the moving liquid, so they travel at different speeds and exit at different times. A detector records these eluting bands as peaks, and peak area or height relates to amount. The technique supports testing in pharmaceuticals, foods, environmental samples, and industrial chemicals. Quantification usually depends on calibration with known standards.
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.
Primary myelofibrosis (PMF) is a rare bone marrow blood cancer. It is classified by the World Health Organization (WHO) as a type of myeloproliferative neoplasm, a group of cancers in which there is activation and growth of mutated cells in the bone marrow. This is most often associated with a somatic mutation in the JAK2, CALR, or MPL genes. In PMF, the bony aspects of bone marrow are remodeled in a process called osteosclerosis; in addition, fibroblasts secrete collagen and reticulin proteins that are collectively referred to as fibrosis. These two pathological processes compromise the normal function of bone marrow, resulting in decreased production of blood cells such as erythrocytes (red cells), granulocytes, and megakaryocytes. The latter are responsible for the production of platelets. Signs and symptoms include fever, night sweats, bone pain, fatigue, and abdominal pain. Increased infections, bleeding and an enlarged spleen (splenomegaly) are also hallmarks of the disease. Patients with myelofibrosis have an increased risk of acute meyloid leukemia and frank bone marrow failure. In 2016, prefibrotic primary myelofibrosis was formally classified as a distinct condition that progresses to overt PMF in many patients, the primary diagnostic difference being the grade of fibrosis.
=== Radio === On 5 August 2012, Willis began co-presenting Sunday Morning Breakfast with Stephen Mulhern across the Heart network. The Show ended in 2018. It was announced in December 2025 that Willis would present a new BBC Radio 2 show beginning in January 2026. The show would run from 1-3pm on Saturdays.
== Pharmacology == Lisinopril is the lysine-analog of enalaprilat, the active metabolite of enalapril. Unlike other ACE inhibitors, it is not a prodrug, is not metabolized by the liver, and is excreted unchanged in the urine.
== Further reading == Hồ NT, Hughes SG, Ta VT, Phan LT, Đỗ Q, Nguyễn TV, et al. (May 2024). "Safety, immunogenicity and efficacy of the self-amplifying mRNA ARCT-154 COVID-19 vaccine: pooled phase 1, 2, 3a and 3b randomized, controlled trials". Nature Communications. 15 (1) 4081. Bibcode:2024NatCo..15.4081H. doi:10.1038/s41467-024-47905-1. PMC 11094049. PMID 38744844.
=== Genetic engineering and drug-based interventions === More recently, research has explored the use of genetic engineering and pharmaceuticals as potential treatments. tRNA therapies have emerged in research studies as a potential missense mutation treatment, following evidence supporting their use in nonsense mutation correction. Missense-correcting tRNAs are engineered to identify the mutated codon, but carry the correct charged amino acid which is inserted into the nascent protein. Pharmaceuticals that target specific proteins affected by missense mutations have also shown therapeutic potential. Pharmaceutical studies have particularly focused on targeting the p53 mutant protein and Ca2+ channel abnormalities, both caused by gain of function missense mutations due to their high prevalence in a number of cancers and genetic diseases respectively. In cystic fibrosis, most commonly caused by missense mutations, drugs known as modulators target the defective Cystic fibrosis transmembrane conductance regulator (CFTR) protein. For example, to reduce the defects caused by class III CFTR mutations, Ivacaftor, part of the modulator Kalydeco, forces the chloride channel to remain in an open position.
Sources: en.wikipedia.org
The CoRR Hypothesis proposes that this co-location of genes with their gene products is required for redox regulation of gene expression, and accounts for the persistence of DNA in bioenergetic organelles.
Plasma renin activity (PRA), also known as the renin (active) assay or random plasma renin, is a measure of the activity of the plasma enzyme renin, which plays a major role in the body's regulation of blood pressure, thirst, and urine output. Measure of direct renin concentration (DRC) is technically more demanding, and hence PRA is used instead. DRC assays are still in evolution, and generally a conversion factor of PRA (ng/mL/h) to DRC (mU/L) is 8.2. A recently developed and already commonly used automated DRC assay uses the conversion factor of 12. PRA is sometimes measured, specially in case of certain diseases which present with hypertension or hypotension. PRA is also raised in certain tumors. A PRA measurement may be compared to a plasma aldosterone concentration as an aldosterone-to-renin ratio (ARR).
=== Plan Colombia === Plan Colombia was a joint security scheme spearheaded by the US and in cooperation with Colombia from 2000 to 2015. The Plan aimed to decrease drug cultivation in Colombia, decrease drug cartel and left-wing insurgency (FARC) violence, and spur economic growth in Colombia. It involved sending trillions in economic and military support to Colombia. Around 80% of the funding was military aid, and overall, the anti-insurgency component of the plan cost the US $500 billion.Paley argues that this heavily security-focused funding was purposeful, as it developed Colombia into an environment that was much more stable to allow foreign investment into the country's natural resource wealth, something she argues was the plans true intention. The US government justified their militarisation of Colombia and their targeting of the FARC in the plan by accusing them of being drug lords, framing their removal as necessary to protect Americans from FARC-trafficked drugs. US security organisations increasingly labelled them as major traffickers throughout the early 2000s. However, in reality, the FARC were not major contributors to the trade at all- in 2001, the Colombian government estimated that paramilitary groups controlled around 40% of the drug trade in the country, whilst the FARC only controlled 2.5%. Despite the erroneous accusation by the US government, the intensified security efforts of Plan Colombia ultimately reduced FARC numbers by around half.
=== Mass Spectrometry === Mass spec techniques are essential in nuclear forensics analysis. Mass spec can provide elemental and isotopic information. Mass spec also requires less sample mass relative to counting techniques. For nuclear forensic purposes it is essential that the mass spectrometry offers excellent resolution in order to distinguish between similar analytes, e.g. 235U and 236U. Ideally, mass spec should offer excellent resolution/mass abundance, low backgrounds, and proper instrumental function.
Sources: en.wikipedia.org
=== Approval of discoveries === In December 2015, the conclusions of a new JWP report were published by IUPAC in a press release, in which element 113 was awarded to Riken; elements 115, 117, and 118 were awarded to the collaborations involving the JINR. A joint 2016 announcement by IUPAC and IUPAP had been scheduled to coincide with the publication of the JWP reports, but IUPAC alone decided on an early release because the news of Riken being awarded credit for element 113 had been leaked to Japanese newspapers. For the first time in history, a team of Asian physicists would name a new element. The JINR considered the awarding of element 113 to Riken unexpected, citing their own 2003 production of elements 115 and 113, and pointing to the precedents of elements 103, 104, and 105 where IUPAC had awarded joint credit to the JINR and LBNL. They stated that they respected IUPAC's decision, but reserved determination of their position for the official publication of the JWP reports. The full JWP reports were published on 21 January 2016. The JWP recognised the discovery of element 113, assigning priority to Riken. They noted that while the individual decay energies of each nuclide in the decay chain of 278113 were inconsistent, their sum was now confirmed to be consistent, strongly suggesting that the initial and final states in 278113 and its daughter 262Db were the same for all three events. The decay of 262Db to 258Lr and 254Md was previously known, firmly anchoring the decay chain of 278113 to known regions of the chart of nuclides.
== Menu and advertising == The first Taco Bell commercials premiered in 1968, featuring advertisements with Mel Blanc, Pat Harrington, and the then-host of Truth or Consequences, Bob Barker. In 1992, Johnny Cash starred in a television commercial for Taco Bell's value menu. In 1993, Taco Bell was used as product placement and plot device in the movie Demolition Man updating their currently used logo. From August 1997 to July 2000, Gidget the Chihuahua was the brand's advertising mascot, a campaign developed by TBWA. Voiced by Carlos Alazraqui, slogans included “¡Yo quiero Taco Bell!” (I want Taco Bell!), “Drop the Chalupa,” and “¡Viva Gorditas!” All became catchphrases in popular culture. In 2000, Taco Bell: Tasty Temple Challenge was released for DOS by Taco Bell as the publisher and developed by BrandGames as a kid-friendly first-person 3D action shooter with gameplay similar to that of Doom and Wolfenstein 3D in terms of combat and exploration, serving as an advertisement for the brand. The player controls Baja Bill, who explores a temple of a lost jungle civilization, battling snakes and scorpions with Taco Bell's hot and wild sauce. Food from the brand also appears in game and is used to replenish the protagonist's health.
== Species distribution == Across vertebrates, four paralogous TCAPs (TCAP-1–4) exhibit structural similarity to corticotropin-releasing hormone (CRH) and other secretin-family peptides and have been shown in rodent and non-mammalian models to exert anxiolytic-like effects, modulate glucose and energy homeostasis, and participate in broader tissue-specific signaling, highlighting TCAPs as evolutionarily conserved peptides.
Sources: en.wikipedia.org
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.
An HPLC method is typically validated before its routine use and revalidated in part when significant changes affect the method. Regulators do not set a universal calendar interval. The need for revalidation depends on the change, its risk, and the applicable guidance.
Validation establishes that a method is suitable for its intended purpose, often through a planned study. Verification confirms that a laboratory can reproduce a previously validated or compendial method under its own conditions. Verification is usually narrower than full validation.
Method validation is the documented process of confirming that an HPLC procedure is suitable for its intended use. It evaluates accuracy, precision, specificity, linearity, range, detection limits, and robustness. Validation criteria depend on the regulatory context and the sample type.