This is a working overview of HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-09-17. Anything still debated is marked as such rather than presented as settled.
Regulatory status varies by country. In the United States, creatine monohydrate is sold as a dietary supplement ingredient, while in the European Union it is placed on the market as a food supplement component. Some jurisdictions have established purity monographs or permitted health claims, while others treat it as a novel food or require notification. Product labels may state the amount of creatine monohydrate or the equivalent creatine content, and the two figures can differ. Independent testing programs sometimes check identity, potency, and contaminant limits.
Creatine monohydrate is stable under dry, cool conditions but can degrade when exposed to moisture and heat. In solution, it undergoes hydrolysis to creatinine, a cyclic derivative with little role in phosphagen energy transfer. The rate of conversion increases with temperature, storage time, and acidic or alkaline pH. Solid material kept in a sealed container at room temperature generally retains its composition for extended periods. Moisture uptake is a primary concern because it can accelerate breakdown and caking.
Quality assessment of creatine monohydrate typically uses high-performance liquid chromatography to separate creatine from creatinine and other impurities. Other methods include nuclear magnetic resonance spectroscopy, titration, and infrared spectroscopy for identity confirmation. Purity is often reported as a percentage of the labeled compound on a dry basis, while moisture content is measured separately. Because different analytical methods have different selectivity, comparing purity values across sources requires attention to the method and sample preparation.
In dry solid form, creatine monohydrate is relatively stable when protected from moisture and heat. The crystal lattice includes water, and exposure to high humidity can cause caking or gradual changes in powder flow. Elevated temperatures may accelerate decomposition, particularly if moisture is present. Studies generally report that sealed, dry material retains acceptable purity for extended periods, although exact shelf life depends on packaging and storage conditions. Light exposure is not usually considered a major factor for this compound.
In aqueous solution, creatine monohydrate undergoes a slow conversion to creatinine, a cyclized degradation product. This reaction is pH- and temperature-dependent, and it proceeds faster in warm or alkaline conditions. Because the conversion is gradual, analytical measurements of creatine in solution must account for time and storage history. The equilibrium favors creatinine more strongly at higher temperatures, which is relevant to sample handling in laboratories and to beverage formulations. Refrigeration slows but does not entirely stop this process.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | 15-25 °C | Sealed container; protect from moisture and direct heat. |
| Theoretical water content | About 12.1% | One water molecule per creatine molecule. |
| Primary degradation product | Creatinine | Formed by cyclization, especially in aqueous solution. |
| Common analytical method | HPLC-UV | Used to separate creatine from creatinine and related impurities. |
| Regulatory classification (U.S.) | Dietary supplement ingredient | Other jurisdictions may classify it as a food supplement or novel food depending on rules. |
In the body, creatine is synthesized from the amino acids arginine, glycine, and methionine, primarily in the liver and kidneys. It is transported to muscle and other tissues, where it is phosphorylated to phosphocreatine by creatine kinase. This phosphagen system provides a rapid source of adenosine triphosphate during short, intense contractions. Dietary creatine comes mainly from meat and fish, and the body's total pool is influenced by both synthesis and intake.
As a supplement, creatine monohydrate is studied for its effects on muscle performance and recovery. The compound is often described as an ergogenic aid, meaning it may support physical work capacity. Research typically compares it with placebo or other forms, such as citrate or nitrate, under controlled conditions. Questions remain about the optimal dose and long-term effects in different populations, and findings are not uniform across all studies. The monohydrate form remains the most extensively tested.
Creatine monohydrate is a crystalline compound formed from creatine and one molecule of water. Its systematic name is N-(aminoiminomethyl)-N-methylglycine monohydrate, and it appears as a white, odorless powder with limited solubility in water. The monohydrate is the most common solid form used in research and commercial products because it is stable under dry conditions. The anhydrous form lacks the water of crystallization and differs slightly in molar mass. Both forms participate in the same biochemical reactions once dissolved.
Solid creatine monohydrate is generally stable when kept dry and protected from extremes of heat and humidity. In the presence of moisture, it can gradually convert to creatinine, a cyclic dehydration product that has little value for phosphocreatine synthesis. Elevated temperatures and acidic conditions accelerate this conversion in solution. Because the reaction is slow in cool, dry storage, typical shelf lives are measured in years rather than weeks. Packaging that limits moisture and oxygen exposure helps maintain purity.
Recommended storage usually involves a sealed container kept at room temperature, away from direct sunlight and moisture. High humidity can cause caking, which changes flow properties and may complicate accurate weighing. Repeated opening of containers exposes the powder to air and moisture, so smaller aliquots can reduce handling effects. Storage temperature ranges are not absolute requirements; they reflect conditions that slow degradation and preserve consistent physical characteristics. Clean, dry tools help prevent contamination during sampling.
Laboratory analysis of creatine monohydrate typically uses high-performance liquid chromatography to separate creatine from creatinine and other impurities. Detection may be ultraviolet, refractive index, or mass spectrometric, depending on the laboratory's equipment and the required sensitivity. Nuclear magnetic resonance spectroscopy can quantify the main component and identify related substances. Water content is measured by Karl Fischer titration, which is important because the monohydrate has a defined theoretical hydration level. Heavy metals, residual solvents, and microbial limits are also checked in quality control programs.
Commercial creatine monohydrate is produced mainly by chemical synthesis rather than extraction from animal tissue. Suppliers provide a certificate of analysis listing assay, water content, and impurity limits, and some products undergo third-party testing. Verification of identity can use infrared or Raman spectroscopy alongside chromatographic methods. Storage recommendations generally call for a cool, dry place and a tightly closed container to limit moisture uptake. Open questions include how packaging, flavoring agents, and long-term storage affect the stability of finished products.
Dry creatine monohydrate is generally stable when kept sealed and protected from heat and moisture. In solution, however, creatine undergoes a slow cyclization to creatinine, a related compound with no role in phosphocreatine storage. The rate of this conversion increases with temperature and is influenced by pH. Because creatinine is a common impurity in liquid or poorly stored products, analytical testing often measures both compounds. The crystalline monohydrate is less prone to degradation than aqueous preparations, though caking can occur if moisture enters the container.
== Vasoactive intestinal peptide (VIP) == Vasoactive intestinal peptide (VIP) is a 28-residue amino acid peptide first characterized in 1970 that was initially isolated from porcine duodenum. A member of the secretin/glucagon hormone superfamily, VIP was initially discovered owing to its potent vasodilatory effects (as its name implies). VIP is widely distributed in the central and peripheral nervous system as well as in the digestive, respiratory, reproductive, and cardiovascular systems as a neurotransmitter and neuroendocrine releasing factor. These effects contribute to an extensive range of physiological and pathological processes related to development, growth, and the control of neuronal, epithelial, and endocrine cell function.
==== Binding RuBP ==== Carbamylation of the ε-amino group of Lys210 is stabilized by coordination with the Mg2+. This reaction involves binding of the carboxylate termini of Asp203 and Glu204 to the Mg2+ ion. The substrate RuBP binds Mg2+ displacing two of the three aquo ligands.
From 1951 Sanger was a member of the external staff of the Medical Research Council and when they opened the Laboratory of Molecular Biology in 1962, he moved from his laboratories in the Biochemistry Department of the university to the top floor of the new building. He became head of the Protein Chemistry division. Prior to his move, Sanger began exploring the possibility of sequencing RNA molecules and began developing methods for separating ribonucleotide fragments generated with specific nucleases. This work he did while trying to refine the sequencing techniques he had developed during his work on insulin. The key challenge in the work was finding a pure piece of RNA to sequence. In the course of the work he discovered in 1964, with Kjeld Marcker, the formylmethionine tRNA which initiates protein synthesis in bacteria. He was beaten in the race to be the first to sequence a tRNA molecule by a group led by Robert Holley from Cornell University, who published the sequence of the 77 ribonucleotides of alanine tRNA from Saccharomyces cerevisiae in 1965. By 1967 Sanger's group had determined the nucleotide sequence of the 5S ribosomal RNA from Escherichia coli, a small RNA of 120 nucleotides.
== Cost == Monoclonal antibodies are more expensive to manufacture than small molecules due to the complex processes involved and the general size of the molecules, all in addition to the enormous research and development costs involved in bringing a new chemical entity to patients. They are priced to enable manufacturers to recoup the typically large investment costs, and where there are no price controls, such as the United States, prices can be higher if they provide great value. Seven University of Pittsburgh researchers concluded, "The annual price of mAb therapies is about $100,000 higher in oncology and hematology than in other disease states", comparing them on a per patient basis, to those for cardiovascular or metabolic disorders, immunology, infectious diseases, allergy, and ophthalmology.
Red blood cell concentrates are produced either from whole blood or by apheresis. Production from whole blood is far more common than apheresis due to collection and production efficacy as well as economical purposes. When red blood cell concentrates are produced from whole blood, the whole blood is first separated through centrifugation (usually between 3000 to 5000 x g). The red blood cells are denser than plasma and the other present blood cells (platelets, white blood cells) and settle at the bottom of the blood bag. After centrifugation, the red blood cells are separated from the other components (the majority of the plasma, platelets and white blood cells) through the use of an extractor (also referred to as blood press). After extraction, an additive solution is usually added in a ratio of 1:1.5 to 1:2. The purpose of the additive solution is to maintain adequate viscosity, provide nutrients and ATP/GTP building blocks and reduce haemolysis generation throughout blood bank storage. Choice of additive solution has an impact on the red blood cell viability and, thereby, shelf life (expiry date) of the red blood cell concentrate. Usually, shelf life is limited to 4 to 6 weeks, provided that the red blood cell concentrates are stored in adequate conditions (2-6 °C). Commercial additive solutions are typically based on saline. They usually contain glucose, adenine, mannitol and, sometimes, phosphate and guanosine. The additive solution has no, or very little, buffering capacity, but buffering is provided by the red blood cells themselves.
Sources: en.wikipedia.org
The HAIR-AN syndrome is a rare subtype of polyendocrine metabolic ovarian syndrome (PMOS) characterized by hyperandrogenism (HA), insulin resistance (IR) and acanthosis nigricans (AN). The symptoms of the HAIR-AN syndrome are largely due to severe insulin resistance, which can be secondary to blocking antibodies against the insulin receptor or genetically absent/reduced insulin receptor number/function. Insulin resistance leads to hyperinsulinemia which, in turn, leads to an excess production of androgen hormones by the ovaries. High levels of androgen hormones (hyperandrogenism) in females causes excessive hair growth, acne and irregular menstruation. Patients with both underlying mechanisms of insulin resistance may have more severe hyperandrogenism. Insulin resistance is also associated with diabetes, heart disease and excessive darkening of the skin (acanthosis nigricans)
=== Exhibits === The museum debuted a new exhibit on November 22, 2013. It consists of the engine of the Missouri Packet, the first steamboat to sink in the Missouri River in 1820. The Hawleys excavated its engine in 1987, just outside the small town of Arrow Rock, Missouri. It did not yield many other artifacts, yet still inspired the Hawleys to continue their quest for sunken steamboats. David Hawley told The Kansas City Star, "An engine like this has never been on display." He believes it to be the oldest extant maritime steam engine in the United States. In January 2013, the museum was closed for the first time in its 20-year history, to repair the ceiling and have the displays cleaned, reorganized, and expanded.
=== Online resale === Buc-ee's does not operate its own online store. However, several third-party resellers offer Buc-ee's products through various platforms, including Amazon, Walmart Marketplace, eBay, Etsy, and dedicated websites such as Texas Snax, True Texas Merch, and Johnny's Goods. These resellers operate under the first-sale doctrine, which permits the resale of legitimately purchased products. Buc-ee's states on its Web site that such resellers "are not affiliated with, authorized, sponsored, or endorsed by Buc-ee's in any way." Texas Snax, founded by Chris J. Koerner in 2020, emerged as one of the largest dedicated Buc-ee's resellers after Koerner initially contacted the company about a partnership and received no response. When Buc-ee's legal team learned of his venture, they permitted it on the condition that he change the original Web site name and add a disclaimer clarifying that Texas Snax is not affiliated with Buc-ee's. Online prices for Buc-ee's products are typically marked up significantly compared to in-store prices.
=== Monk === On February 14, 2025, Jonathan Monk became the third offender of the case to stand trial for the 2017 Pasquotank County prison murders. Jury selection lasted from February to March 2025. On March 18, 2025, the jury found Monk guilty of all 13 criminal charges, including four counts of first degree murder. During the sentencing phase, the defence sought to seek mercy for Monk and implored the jury to sentence Monk to life without parole, on account of Monk's troubled childhood, caused by his mother's neglect and that his early exposure to abuse caused long-lasting psychological issues to him while growing up. On March 27, 2025, 38-year-old Jonathan Monk was sentenced to death by Judge Jeffery B. Foster upon the jury's unanimous recommendation for capital punishment. Apart from the four death sentences, Monk also received 60 to 81 years in prison for attempted first degree murder, felony burning a public building, felony attempted escape, and felony riot. Monk was transferred into the Federal Bureau of Prisons system and was held at USP Lee briefly before joining Brady and Buckman at ADX Florence on December 23, 2025.
Sources: en.wikipedia.org
A sealed container at room temperature, away from moisture and direct heat, is suitable for most solid material. Keeping the lid closed limits water uptake and caking. Long-term storage in a refrigerator is not necessary if the powder remains dry.
Heat, moisture, and prolonged time in solution promote conversion to creatinine. The reaction is faster at higher temperatures and at pH values far from neutral. Dry powder is much more stable than dissolved material.
Common methods include high-performance liquid chromatography for creatine and creatinine, plus water-content analysis by Karl Fischer titration. Heavy metals, residual solvents, and microbial limits may also be tested. A specification may list total creatine content and impurity limits.
Dry, sealed creatine monohydrate can remain stable for years, but storage conditions affect its shelf life. Moisture, heat, and repeated opening of containers can reduce quality over time.