Everything below concerns Limit of detection. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-09-13. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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 |
Routine HPLC testing compares a sample result with a calibration curve prepared from known reference standards. Peak area or peak height is plotted against concentration, and the curve is used to estimate unknown amounts. Retention time supports tentative identification when compared with a standard, though mass spectrometry or another confirmatory method may be needed for definitive identification. Pre-run checks verify repeatability, resolution, and peak symmetry before sample analysis. Limits of detection and quantification describe the smallest amounts that can be reliably observed or measured. Sample preparation, filtration, and degassing help prevent column damage and inconsistent results.
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.
In 1884, Svante Arrhenius attributed the properties of acidity to hydrogen cations (H+), later described as protons or hydrons. An Arrhenius acid is a substance that, when added to water, increases the concentration of H+ ions in the water. Chemists often write H+(aq) and refer to the hydrogen cation when describing acid–base reactions but the free hydrogen nucleus, a proton, does not exist alone in water, it exists as the hydronium ion (H3O+) or other forms (H5O2+, H9O4+). Thus, an Arrhenius acid can also be described as a substance that increases the concentration of hydronium ions when added to water. Examples include molecular substances such as hydrogen chloride and acetic acid. An Arrhenius base, on the other hand, is a substance that increases the concentration of hydroxide (OH−) ions when dissolved in water. This decreases the concentration of hydronium because the ions react to form H2O molecules:
is the flow velocity field. The interpretation of the continuity equation for mass is the following: For a given closed surface in the system, the change, over any time interval, of the mass enclosed by the surface is equal to the mass that traverses the surface during that time interval: positive if the matter goes in and negative if the matter goes out. For the whole isolated system, this condition implies that the total mass
In all, over a million Canadians served in the armed forces during the Second World War. Canadian troops played important roles in many key battles of the war, including the failed 1942 Dieppe Raid, the Allied invasion of Italy, the Normandy landings, the Battle of Normandy, and the Battle of the Scheldt in 1944. Canada provided asylum for the Dutch monarchy while that country was occupied and is credited by the Netherlands for major contributions to its liberation from Nazi Germany.
Food Administration International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) African Union: African Medicines Agency Australia: Therapeutic Goods Administration Brazil: National Health Surveillance Agency Canada: Marketed Health Products Directorate Canada: Health Canada Denmark: Danish Medicines Agency European Union: European Food Safety Authority and European Medicines Agency Germany: Federal Institute for Drugs and Medical Devices India: Food Safety and Standards Authority of India and Central Drugs Standard Control Organization Japan: Ministry of Health, Labour and Welfare (MHLW) Japan: Pharmaceuticals and Medical Devices Agency Mexico: Federal Commission for the Protection against Sanitary Risk Philippines: Food and Drug Administration (FDA) Singapore: Health Sciences Authority United Kingdom: Food Standards Agency and Medicines and Healthcare products Regulatory Agency
However, by careful optimization of instrument parameters which cause ion heating, hydrogen scrambling can be minimized to a degree which preserves the solution phase isotopic labeling until fragmentation can be performed using a technique where scrambling does not occur. More recently, ultraviolet photodissociation (UVPD) has also been investigated as a possible fragmentation technique to localize deuterium within peptides and proteins. In this regard, the conclusions have been mixed, while it is possible to obtain UVPD fragments which has not undergone scrambling under certain conditions, others have shown that scrambling can occur for both peptides and proteins during the UVPD fragmentation step itself. The theory consolidating these apparent contradictions has to do with the dual fragmentation pathway that may arise from UV irradiation of peptides and proteins, i.e. direct and statistical dissociation. That is, if experimental conditions favor direct dissociation and the precursor ion is kept at low internal energies before and during fragmentation the deuterium level of the resulting fragments will correspond to the non-scrambled precursor. However, experimental conditions may favor statistical dissociation during UV irradiation, especially at long irradiation times and low gas pressure, leading to internal conversion of the electronic excitation energy contributed by the UV photons. The result is vibrational excitation of the irradiated molecule which in turn undergo scrambling.
Sources: en.wikipedia.org
== History == JWD InfoLogistics started its business with home and office moving services under the name of JVK International Movers Company Limited in 1979. The company later expanded its portfolio of business into the logistics and supply chain industry and converted into a public company and listed in the Stock Exchange of Thailand on September 29, 2015. JWD Group decided to cooperate with Flash Group and Thailand Post to launch the Cold Chain Express named Fuze Post on September 1, 2021. In 2023, JWD InfoLogistics merged with SCG Logistics Management Co.,Ltd (SCGL) and was renamed SCGJWD Logistics Public Company Limited SCGJWD operates in 9 ASEAN countries plus China and has over 2,400 corporate customers.
Oxycodone was first made available in the United States in 1939. In the 1970s, the FDA classified oxycodone as a Schedule II drug, indicating a high potential for non-medical use and addiction. After its 1995 approval by the FDA by Deputy Director Curtis Wright IV, Purdue Pharma introduced OxyContin, a controlled release formulation of oxycodone in 1996. However, drug users quickly learned how to simply crush the controlled release tablet to swallow, inhale, or inject the high-strength opioid for a powerful morphine-like high. In fact, Purdue's private testing conducted in 1995 determined that 68% of the oxycodone could be extracted from an OxyContin tablet when crushed. In 2007, Purdue paid $600 million in fines after being prosecuted for making false claims about the risk of opioid use disorder associated with oxycodone. In 2010, Purdue Pharma reformulated OxyContin, using a polymer to make the pills extremely difficult to crush or dissolve in water to reduce non-medical use of OxyContin. The FDA approved relabeling the reformulated version as abuse-resistant. OxyContin use following the 2010 reformulation declined slightly while no changes were observed in the use of other opioids. In June 2017, the FDA asked the manufacturer to remove its long-acting form of oxymorphone (Opana ER) from the US market, because the drug's benefits may no longer outweigh its risks, this being the first time the agency has asked to remove a currently marketed opioid pain medication from sale due to public health consequences of non-medical use.
=== Other symptoms and links to disease === Symptoms, whether connected or not to GS, have been reported in a subset of those affected: fatigue (feeling tired all the time), difficulty maintaining concentration, unusual patterns of anxiety, loss of appetite, nausea, abdominal pain, weight loss, itching (with no rash), and others, such as humor change or depression. But scientific studies found no clear pattern of adverse symptoms related to the elevated levels of unconjugated bilirubin in adults. However, other substances glucuronidated by the affected enzymes in those with Gilbert's syndrome could theoretically, at their toxic levels, cause these symptoms. Consequently, debate exists about whether GS should be classified as a disease. Gilbert syndrome has been linked to an increased risk of gallstones, schizophrenia, breast cancer, and colorectal cancer. The theorized mechanism for the increased risk of breast cancer is elevated estrogen from its decreased metabolism by UDP-glucuronosyltransferase (UGT) in those with Gilbert syndrome. The cause for the increased risk of schizophrenia is not yet fully understood and is the object of further research.
The central pathways of metabolism described above, such as glycolysis and the citric acid cycle, are present in all three domains of living things and were present in the last universal common ancestor. This universal ancestral cell was prokaryotic and probably a methanogen that had extensive amino acid, nucleotide, carbohydrate and lipid metabolism. The retention of these ancient pathways during later evolution may be the result of these reactions having been an optimal solution to their particular metabolic problems, with pathways such as glycolysis and the citric acid cycle producing their end products highly efficiently and in a minimal number of steps. The first pathways of enzyme-based metabolism may have been parts of purine nucleotide metabolism, while previous metabolic pathways were a part of the ancient RNA world. Many models have been proposed to describe the mechanisms by which novel metabolic pathways evolve. These include the sequential addition of novel enzymes to a short ancestral pathway, the duplication and then divergence of entire pathways as well as the recruitment of pre-existing enzymes and their assembly into a novel reaction pathway. The relative importance of these mechanisms is unclear, but genomic studies have shown that enzymes in a pathway are likely to have a shared ancestry, suggesting that many pathways have evolved in a step-by-step fashion with novel functions created from pre-existing steps in the pathway.
It was proposed by the researchers that low maximal receptor activation, or lower-efficacy partial agonism, could explain the atypical effects of biased MOR agonists like SR-17018 rather than biased agonism. These results were subsequently reanalyzed and disputed by other researchers. In any case, the exact mechanisms underlying the atypical effects of SR-17018 remain unclear. For example, they may be related to G protein over β-arrestin2 bias, or to differences in G protein-mediated signaling. SR-17018 produces rewarding effects as assessed by conditioned place preference (CPP) in rodents. Its rewarding effects in this assay were comparable to those of morphine. In addition to rewarding effects, SR-17018 produces modest hyperlocomotion in rodents, albeit to a far lesser extent than morphine or fentanyl. Addition of SR-17018 to morphine in rodents attenuates morphine-induced hyperlocomotion whilst increasing analgesic efficacy in mice. Unlike morphine and fentanyl, SR-17018 does not produce locomotor sensitization with chronic administration. A self-administration study of SR-17018 in mice was limited by the drug's poor solubility. However, in a subsequent study, the drug produced self-administration in mice, but was less efficacious than oxycodone or fentanyl. SR-17018 has also been found to produce self-administration in rhesus monkeys, but along with buprenorphine, was less efficacious than heroin in this test.
Sources: en.wikipedia.org
Azacitidine, sold under the brand name Vidaza among others, is a medication used for the treatment of myelodysplastic syndrome, myeloid leukemia, and juvenile myelomonocytic leukemia. It is a chemical analog of cytidine, a nucleoside in DNA and RNA. Azacitidine and its deoxy derivative, decitabine (also known as 5-aza-2′-deoxycytidine) were first synthesized in Czechoslovakia as potential chemotherapeutic agents for cancer. The most common adverse reactions in children with juvenile myelomonocytic leukemia include pyrexia, rash, upper respiratory tract infection, and anemia.
Studies have shown that common misconceptions about the effectiveness and necessity of antibiotics to treat common mild illnesses contribute to their overuse. Important to the conversation of antibiotic use is the veterinary medical system. Veterinary oversight is required by law for all medically important antibiotics. Veterinarians use the Pharmacokinetic/pharmacodynamic model (PK/PD) approach to ensuring that the correct dose of the drug is delivered to the correct place at the correct timing.
The brown recluse (Loxosceles reclusa, Sicariidae, formerly placed in a family "Loxoscelidae") is a recluse spider with necrotic venom. Similar to those of other recluse spiders, their bites sometimes require medical attention. The brown recluse is one of two spiders in North America with dangerous venom, the other being the black widow. Brown recluse spiders are usually between 6 and 20 millimetres (0.24 and 0.79 in), but may grow larger. While typically light to medium brown, they range in color from whitish to dark brown or blackish gray. The cephalothorax and abdomen are not necessarily the same color. These spiders usually have markings on the dorsal side of their cephalothorax, with a black line coming from it that looks like a violin with the neck of the violin pointing to the rear of the spider, resulting in the nicknames fiddleback spider, brown fiddler, or violin spider.
COLD-PCR (co-amplification at lower denaturation temperature PCR) is a modified polymerase chain reaction (PCR) protocol that enriches variant alleles from a mixture of wildtype and mutation-containing DNA. The ability to preferentially amplify and identify minority alleles and low-level somatic DNA mutations in the presence of excess wildtype alleles is useful for the detection of mutations. Detection of mutations is important in the case of early cancer detection from tissue biopsies and body fluids such as blood plasma or serum, assessment of residual disease after surgery or chemotherapy, disease staging and molecular profiling for prognosis or tailoring therapy to individual patients, and monitoring of therapy outcome and cancer remission or relapse. Common PCR will amplify both the major (wildtype) and minor (mutant) alleles with the same efficiency, occluding the ability to easily detect the presence of low-level mutations. The capacity to detect a mutation in a mixture of variant/wildtype DNA is valuable because this mixture of variant DNAs can occur when provided with a heterogeneous sample – as is often the case with cancer biopsies. Currently, traditional PCR is used in tandem with a number of different downstream assays for genotyping or the detection of somatic mutations. These can include the use of amplified DNA for RFLP analysis, MALDI-TOF (matrix-assisted laser-desorption–time-of-flight) genotyping, or direct sequencing for detection of mutations by Sanger sequencing or pyrosequencing.
Murine respirovirus, now Respirovirus muris, formerly Sendai virus (SeV) and previously also known as murine parainfluenza virus type 1 or hemagglutinating virus of Japan (HVJ), is an enveloped, 150–200 nm diameter, negative sense, single-stranded RNA virus of the family Paramyxoviridae. It typically infects rodents and it is not pathogenic for humans or domestic animals. Respirovirus muris is a member of the genus Respirovirus. The virus was isolated in the city of Sendai in Japan in the early 1950s. Since then, it has been actively used in research as a model pathogen. The virus is infectious for many cancer cell lines (see below), and has oncolytic properties demonstrated in animal models and in naturally occurring cancers in animals. Its ability to fuse eukaryotic cells and to form syncytium was used to produce hybridoma cells capable of manufacturing monoclonal antibodies in large quantities. Recent applications of SeV-based vectors include the reprogramming of somatic cells into induced pluripotent stem cells and vaccine creation. For vaccination purpose the Sendai virus-based constructs could be delivered in a form of nasal drops, which may be beneficial in inducing a mucosal immune response. SeV has several features that are important in a vector for a successful vaccine: the virus does not integrate into the host genome, it does not undergo genetic recombination, it replicates only in the cytoplasm without DNA intermediates or a nuclear phase and it does not cause any disease in humans or domestic animals.
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.
System suitability is a set of checks performed before and during a run to confirm that the instrument, column, and method work as expected. Common checks include resolution, tailing factor, theoretical plates, and relative standard deviation of replicate injections. Failure triggers troubleshooting or method adjustment.