The short version of mobile phase fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-10-08 and is reviewed periodically as new material appears.
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.
High-performance liquid chromatography testing separates components of a liquid sample by forcing a mobile phase through a packed column. The stationary phase inside the column interacts with analytes to different degrees, so each compound exits at a characteristic retention time. A pump delivers solvent at controlled flow and pressure, while an injector introduces a precise sample volume. Detectors such as ultraviolet-visible, fluorescence, refractive index, or mass spectrometric instruments record the separated bands. The resulting chromatogram provides qualitative and quantitative information about the mixture.
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.
| 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 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.
Also the cyclization of acetylene to cyclooctatetraene uses metal carbonyl catalysts: In the Monsanto and Cativa processes, acetic acid is produced from methanol, carbon monoxide, and water using hydrogen iodide as well as rhodium and iridium carbonyl catalysts, respectively. Related carbonylation reactions afford acetic anhydride.
=== Pharmacokinetics (PK) === Pharmacokinetic models are constructs aimed at characterizing the average pharmacokinetic behavior of a drug within a population. By incorporating inter-individual variability, these models provide insights into central tendencies and variabilities in drug responses across diverse patient groups. Their application extends to the optimization of dosing regimens at a population level.
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Shakey's Pizza is a pizza restaurant chain based in the United States and the Philippines. Founded in 1954, it was the first franchise pizza chain in the United States. In 1968, the chain had 342 locations. As of April 2026, the chain had about 500 stores globally and 43 in the United States. Currently, the stores can be found in the states of California and Washington, as well as in the Philippines, Singapore and Japan.
Allergic diseases are caused by inappropriate immunological responses to harmless antigens driven by a TH2-mediated immune response. Many bacteria and viruses elicit a TH1-mediated immune response, which down-regulates TH2 responses. The first proposed mechanism of action of the hygiene hypothesis was that insufficient stimulation of the TH1 arm of the immune system leads to an overactive TH2 arm, which in turn leads to allergic disease. In other words, individuals living in too sterile an environment are not exposed to enough pathogens to keep the immune system busy. Since our bodies evolved to deal with a certain level of such pathogens, when they are not exposed to this level, the immune system will attack harmless antigens. Thus, normally benign microbial objects—like pollen—will trigger an immune response. The hygiene hypothesis was developed to explain the observation that hay fever and eczema, both allergic diseases, were less common in children from larger families, which were, it is presumed, exposed to more infectious agents through their siblings, than in children from families with only one child. It is used to explain the increase in allergic diseases that have been seen since industrialization, and the higher incidence of allergic diseases in more developed countries. The hygiene hypothesis has now expanded to include exposure to symbiotic bacteria and parasites as important modulators of immune system development, along with infectious agents. Epidemiological data support the hygiene hypothesis.
Sources: en.wikipedia.org
== Production == The commonly used radioisotopes have short half lives and so do not occur in nature in large amounts. They are produced by nuclear reactions. One of the most important processes is absorption of a neutron by an atomic nucleus, in which the mass number of the element concerned increases by 1 for each neutron absorbed. For example,
=== Names === Relugolix is the generic name of the drug and its INNTooltip International Nonproprietary Name, USANTooltip United States Adopted Name, and JANTooltip Japanese Accepted Name. It is also known by its former developmental code names RVT-601 and TAK-385. Relugolix is sold under the brand name Orgovyx for the treatment of prostate cancer and under the brand name Relumina for the treatment of uterine fibroids. Relugolix compounded with estradiol hemihydrate and norethindrone is sold under the brand name Myfembree for the treatment of uterine fibroids.
On March 11, 1997, National Semiconductor Corporation announced the US$550 million sale of a reconstituted Fairchild to the management of Fairchild with the backing of Sterling LLC, a unit of Citicorp Venture Capital. Fairchild carried with it what was mostly the Standard Products group previously segregated by Amelio. Incidentally, the effective price of acquisition of Cyrix was also US$550 million. On November 17, 1997, National Semiconductor and Cyrix announced the merger of the companies. Cyrix would become an autonomous wholly owned subsidiary. Halla had earlier emphasized that National was after the low-end CPU market as part of the system-on-a-chip pursuit and therefore would not place emphasis on Cyrix's current development of high-end 6x86MX design. However, Cyrix later announced that its merger with National Semiconductor would not change its development or marketing plans. The acquisition of an independent-minded Cyrix subsequently turned National Semiconductor from a collaborator into a competitor with Intel. National lost its business with Intel. Intel reinstated the relationship after the sale of Cyrix. The acquisition of Cyrix also carried with it a business obligation to use the IBM Microelectronics Division to fabricate the Cyrix chips, as well as technical constraint to do the same, while National Semiconductor had plans to transfer their fabrication to its South Portland fab. National incurred huge losses in its processor business and announced the sale of Cyrix to VIA in 1999.
Cytochrome P-450 is not a single enzyme, but rather consists of a closely related family of 50 isoforms; six of them metabolize 90% of drugs. There is a tremendous diversity of individual P-450 gene products, and this heterogeneity allows the liver to perform oxidation on a vast array of chemicals (including most drugs) in phase 1. Three important characteristics of the P-450 system have roles in drug-induced toxicity:
Nylon 66 can have multiple parallel strands aligned with their neighboring peptide bonds at coordinated separations of exactly six and four carbons for considerable lengths, so the carbonyl oxygens and amide hydrogens can line up to form interchain hydrogen bonds repeatedly, without interruption (see the figure opposite). Nylon 510 can have coordinated runs of five and eight carbons. Thus parallel (but not antiparallel) strands can participate in extended, unbroken, multi-chain β-pleated sheets, a strong and tough supermolecular structure similar to that found in natural silk fibroin and the β-keratins in feathers. (Proteins have only an amino acid α-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted H-bonded sheets with mixed directionalities, but the β-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon chain depends on rotations about the 109.47° tetrahedral bonds of singly bonded carbon atoms. When extruded into fibers through pores in an industry spinneret, the individual polymer chains tend to align because of viscous flow. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength. In practice, nylon fibers are most often drawn using heated rolls at high speeds. Block nylon tends to be less crystalline, except near the surfaces due to shearing stresses during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistranded nylon cord and rope is slippery and tends to unravel.
Sources: en.wikipedia.org
Dial-out PCR: a highly parallel method for retrieving accurate DNA molecules for gene synthesis. A complex library of DNA molecules is modified with unique flanking tags before massively parallel sequencing. Tag-directed primers then enable the retrieval of molecules with desired sequences by PCR. Digital PCR (dPCR): used to measure the quantity of a target DNA sequence in a DNA sample. The DNA sample is highly diluted so that after running many PCRs in parallel, some of them do not receive a single molecule of the target DNA. The target DNA concentration is calculated using the proportion of negative outcomes. Hence the name 'digital PCR'. Helicase-dependent amplification: similar to traditional PCR, but uses a constant temperature rather than cycling through denaturation and annealing/extension cycles. DNA helicase, an enzyme that unwinds DNA, is used in place of thermal denaturation. Hot start PCR: a technique that reduces non-specific amplification during the initial set up stages of the PCR. It may be performed manually by heating the reaction components to the denaturation temperature (e.g., 95 °C) before adding the polymerase. Specialized enzyme systems have been developed that inhibit the polymerase's activity at ambient temperature, either by the binding of an antibody or by the presence of covalently bound inhibitors that dissociate only after a high-temperature activation step. Hot-start/cold-finish PCR is achieved with new hybrid polymerases that are inactive at ambient temperature and are instantly activated at elongation temperature.
Novichok agents were designed to be undetectable and unprotectable by NATO equipment, safer to handle, and circumvent the forthcoming Chemical Weapons Convention list of controlled precursors. The Soviet biological weapons program was the world's largest, longest, and most sophisticated biological warfare project. It weaponized and stockpiled the biological agents that cause anthrax, plague, tularemia, smallpox, botulism and others. Genetic engineering improved agent stability and antibiotic resistance. A civilian cover organization named Biopreparat operated 40 to 50 military-purposed biological research facilities. An anti-agriculture program, Ekologiya, targeted crops and livestock. The program employed a peak of 65,000 people and annually produced, for example, 100 tons of smallpox. The Sverdlovsk anthrax leak, which led to at least 68 deaths, began to reveal the extent of the program, continued by defectors including Ken Alibek and Vladimir Pasechnik.
=== Pharmacotherapy === Sodium thiosulfate is commonly prescribed for treatment in patients with calciphylaxis. The actual mechanism of the drug is unknown, but several explanations have been proposed, including chelation of calcium, vasodilation, antioxidant properties, and restoration of endothelial function. Adverse effects of sodium thiosulfate include high anion gap metabolic acidosis and high sodium levels (hypernatremia). Bisphosphonates are a popular choice for the treatment of osteoporosis, but they have also been used to treat calciphylaxis even though the exact mechanism in calciphylaxis is unknown. They are most beneficial in patients who have a genetic ENPP1 deficiency and have been shown to slow development of calciphylaxis lesions in a small prospective study. Cinacalcet (medication parathyroidectomy) is an oral medication that can be used to suppress the parathyroid glands for patients who may not be able to undergo surgical parathyroidectomy. Vitamin K supplementation has also been shown to slow development of calcification in coronary arteries and the aortic valve in older patients. The ability of vitamin K supplementation to slow calcification of blood vessels in calciphylaxis is not well-studied. Warfarin, a vitamin K antagonist discussed above, should be discontinued if possible. Other acceptable treatments may include one or more of the following:
== Further reading == Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4. Kalpakjian, Serope; Schmid, Steven R. (2006), Manufacturing Engineering and Technology (5th ed.), Upper Saddle River, NJ: Pearson Prentice Hall, ISBN 0-13-148965-8
In January 2022, to draw attention, the workers drove around Seoul with the message "Partners' are your biggest asset." Through this Starbucks Korea pledged to hire 1,600 more workers for the stores. Starbucks in Korea has started Siren Order, which is a service that makes online orders available. This has started in 2014, helping customers to order their drinks before their arrival, and picking them up as soon as they arrive. This service has led to nearly 5 million customers to register to the page. As there is high rise in orders, Starbucks in the United States, as well as Canada, Hong Kong, and the United Kingdom has added siren order to their service. To reduce carbon footprint, Starbucks stores in South Korea will be eliminating all single-use cups by 2025. Starbucks stores in Jeju Island will be leading this campaign by only using reusable cups in all 23 stores allocated in the island. The customers can either choose to use their own cups, or deposit 1000 won to use the reusable cups provided by the store. When the cup is returned, the deposit will be returned through cash, Starbucks card or HappyHabit Application points. The reusable cups will be collected and cleaned up by a professional cleaner company, reducing the usage of single-use cups. The reusable cups will also be up-cycled to other forms as well. Starbucks Korea has 870 cashless stores which is about 60% of the whole stores that are available in Korea. Due to this, there has been a reduction of people using cash from 4% in original stores to 0.5% in cashless stores.
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.
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.