This is a working overview of HPLC assay, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-24 and is reviewed periodically as new material appears.
Solid creatine monohydrate is relatively stable when kept dry and sealed, but heat and moisture accelerate its conversion to creatinine. This degradation involves intramolecular cyclization, a process that removes water and forms a less useful compound for phosphocreatine metabolism. Powder stored under cool, dry conditions can remain within specification for extended periods, though exact shelf life depends on packaging, humidity, and initial purity. Aqueous solutions degrade faster than dry powder, with pH and temperature influencing the rate. Because degradation is gradual, analytical testing is used to confirm potency at manufacture and during stability studies.
Quality control for creatine monohydrate typically combines identity, assay, and impurity tests. High-performance liquid chromatography with ultraviolet detection is common for separating creatine from creatinine and related substances. Nuclear magnetic resonance and infrared spectroscopy can confirm molecular structure, while titration may assess acid-base content. Moisture content, heavy metals, residual solvents, and microbial limits are checked according to applicable standards. These tests help distinguish compliant material from powders that have degraded, been diluted, or contain manufacturing residues.
Handling practices aim to limit moisture uptake and thermal exposure. Containers should stay closed when not in use, and storage areas should avoid direct sunlight, strong heat, and high humidity. Caking can occur when powder absorbs water, even if the creatine itself has not fully degraded. Aqueous stock solutions are best prepared fresh when needed because they are less stable than the solid. Open questions include how different excipients, packaging materials, and climate conditions affect long-term stability across global supply chains.
Solid creatine monohydrate is generally stable when kept cool and dry, but it can hydrolyze to creatinine over time. Moisture, heat, and acidic conditions accelerate this conversion, which reduces assay values and changes the material's properties. Creatinine is a cyclic dehydration product that is also a normal human metabolite, so its presence in a sample is not necessarily a health concern by itself. In quality testing, creatinine is monitored as a marker of degradation and purity.
Identity and purity are assessed with several complementary methods. High-performance liquid chromatography can separate creatine from creatinine and related impurities, often with ultraviolet detection. Nuclear magnetic resonance and infrared spectroscopy provide structural confirmation, while Karl Fischer titration measures water content. Elemental analysis and mass spectrometry may be used for additional confirmation, especially in research or forensic settings. No single method captures every quality attribute, so laboratories typically combine results and compare them against a specification.
Creatine monohydrate is sold as a dietary ingredient in some countries and as a food supplement in others. Regulatory frameworks vary, so purity limits, labeling rules, and permitted claims are not globally uniform. In the United States, it falls under dietary supplement rules, whereas the European Union treats it as a food supplement ingredient. Pharmacopeial monographs, where they exist, can provide public quality standards, but not every product is required to meet them. Questions about long-term effects and patterns of use remain areas of active study rather than settled regulatory findings.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | 15–25 °C | Cool, dry, sealed |
| Relative humidity | Below 60% | Moisture promotes caking and degradation |
| Degradation product | Creatinine | Forms by cyclization, especially in solution |
| Assay method | HPLC with UV detection | Often paired with identity tests |
| Aqueous stability | Hours to days at room temperature | Depends on pH, temperature, concentration |
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.
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 the body, creatine is obtained from dietary meat and fish and is also synthesized from arginine, glycine, and methionine. Muscle stores creatine and phosphocreatine, which participate in the rapid regeneration of adenosine triphosphate during short, intense activity. The monohydrate form is used in research because it is chemically defined, stable as a dry solid, and relatively inexpensive to produce. Questions remain about whether other creatine forms offer meaningful advantages in absorption or tissue retention, and findings vary across studies and populations.
Creatine monohydrate is a crystalline compound formed from creatine and one molecule of water. Creatine itself is a nitrogen-containing organic acid that occurs in vertebrate muscle and other tissues. The monohydrate designation refers to the water included in the crystal lattice, not to water added during manufacturing. Its chemical formula is commonly written as C4H9N3O2·H2O. The solid is typically a white, odorless powder with low solubility in water at room temperature. It is one of several creatine forms described in scientific and commercial literature.
The compound was identified in the nineteenth century after chemists isolated a nitrogenous substance from meat extracts. Later work established its role in muscle energy metabolism and its conversion to phosphocreatine. Chemical synthesis of creatine followed, and industrial production made the monohydrate widely available as a purified powder. Interest expanded in the late twentieth century when researchers began studying creatine supplementation and muscle physiology. Historical accounts sometimes differ on exact dates and attributions, but the broad sequence from tissue extracts to synthetic production is well documented.
== Career == Goodacre joined the University of Oxford as a research fellow in 1999. She was a research fellow at the University of East Anglia from 2002. She was described by the BBC as Spider Woman. As of 2018, Goodacre is based at the University of Nottingham, where she founded the SpiderLab in 2007 and leads the ArachNotts research group. As a geneticist, Goodacre studies the evolution, population and conservation of spiders. She monitored the mating behaviour and sex ratio of the linyphiid spider Pityohyphantes phrygianus with Bengt Gunnarsson at the University of Gothenburg. She also studied the silk of Mygalomorphae spiders and the genetic diversity of spider silk genes and found evidence for antimicrobial activity in the silk of common house spiders. She found that Erigone atra, a pest controlling spider, uses long-distance airborne dispersal. Goodacre contributed to the 2011 book Spider Physiology and Behaviour: Physiology. In 2015 Goodacre reported that spiders could survive "sailing" across oceans. ArachNotts study the diving bell spider and its silk, which it uses to build a diving bell in which it stores air underwater, and have so far identified some of the silk genes used by this spider. They also work on the relationship between spiders and the microbes that they carry with them, including the mating behaviour and sex-ratio of offspring, the ecology and biological control potential of spiders in agriculture and the use of genetic tools in the conservation of the endangered raft spider.
Aflatoxins are various poisonous carcinogens and mutagens that are produced by certain molds, especially Aspergillus species such as Aspergillus flavus and Aspergillus parasiticus. According to the USDA, "They are probably the best known and most intensively researched mycotoxins in the world." The fungi grow in soil, decaying vegetation and various staple foodstuffs and commodities such as hay, maize (corn), peanuts, coffee, wheat, millet, sorghum, cassava, rice, chili peppers, cottonseed, tree nuts, sesame seeds, sunflower seeds, and various cereal grains and oil seeds. They have been found in both pet and human foods, as well as in feedstocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into milk, milk products, and meat. For example, contaminated poultry feed is the suspected source of aflatoxin-contaminated chicken meat and eggs in Pakistan. Children are particularly vulnerable to aflatoxin exposure, which is linked to immune suppression, stunted growth, delayed development, aflatoxicosis, and liver cancer. Some studies have reported an association between childhood stunting and aflatoxin exposure, although this link has not been consistently detected in all studies. Furthermore, a causal relationship between childhood stunting and aflatoxin exposure has yet to be conclusively shown by epidemiological studies, though such investigations are underway. Adults have a higher tolerance to exposure, but are also at risk. No animal species is known to be immune. Aflatoxins are among the most carcinogenic substances known.
==== Skeletal muscle ==== Strenuous endurance exercise such as marathons or triathlons can lead to increased cardiac troponin levels in up to one-third of subjects, but it is not linked to adverse health effects in these competitors. High cardiac troponin T levels have also been reported in patients with inflammatory muscle diseases such as polymyositis or dermatomyositis. Troponins are also increased in rhabdomyolysis.
Sources: en.wikipedia.org
Through studies of pronghorn running on treadmills, it has been estimated that the maximum speed that could be achieved aerobically would be 72 km/h (45 mph) for about 10 minutes, so higher speeds such as those reported in Thomson's gazelles, springboks, pronghorn and cheetahs require adaptations for principal use of anaerobic energy sources such as glycogen and creatine phosphate, and could therefore be maintained for only 30–45 seconds when these energy sources are depleted. High acceleration also requires the use of anaerobic energy sources.
San Juan Bautista was built in 1613 by Date Masamune, the daimyō of Sendai in northern Japan, in Tsuki-No-Ura harbour (Ishinomaki, Miyagi Prefecture). The project had been approved by the Bakufu, the shōgun's government in Edo. The shōgun already had two smaller ships (80 and 120 tons) built for him by the English pilot William Adams. The larger, the San Buena Ventura, was given to Spanish shipwrecked sailors to return to New Spain in 1610. The shōgun also issued numerous permits for Red seal ships, destined for Asian trade and incorporating many elements of Western ship design. San Juan Bautista is reported to have required 45 days' work, with the participation of technical experts from the Bakufu, 800 shipwrights, 700 smiths, and 3000 carpenters. Two Spanish men also participated to the endeavour: the friar Luis Sotelo, and the Spanish captain Sebastián Vizcaíno. These efforts were seen with disapproval by the Spanish government in Manila, and Los Rios Coronel suggested that Luis Sotelo should not be allowed into Japan any further (C. R. Boxer).
Magnetic resonance angiography (MRA) generates pictures of the arteries to evaluate them for stenosis (abnormal narrowing) or aneurysms (vessel wall dilatations, at risk of rupture). MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs (called a "run-off"). A variety of techniques can be used to generate the pictures, such as administration of a paramagnetic contrast agent (gadolinium) or using a technique known as "flow-related enhancement" (e.g., 2D and 3D time-of-flight sequences), where most of the signal on an image is due to blood that recently moved into that plane (see also FLASH MRI). Techniques involving phase accumulation (known as phase contrast angiography) can also be used to generate flow velocity maps easily and accurately. Magnetic resonance venography (MRV) is a similar procedure that is used to image veins. In this method, the tissue is now excited inferiorly, while the signal is gathered in the plane immediately superior to the excitation plane—thus imaging the venous blood that recently moved from the excited plane.
During the work carried out in 1967 for the construction of the shopping arcade in the "Centre Bourse" in the heart of Marseille, important archaeological remains were unearthed. The extent of this discovery, which concerned the Greek fortifications of Marseille, funerary enclosures and part of the old port, necessitated the classification of approximately 10,000 m2 (110,000 sq ft) as a historical monument. The remaining area, of about 20,000 m2 (220,000 sq ft), was sacrificed to enable the construction of the Centre Bourse. The excavation lasted ten years and was carried out by the Antiquités historiques and the CNRS. Additional works were carried out later, particularly in 1994. It is in fact a contact area between on the one hand the ancient city which was located north of the current old port and included the hill of Saint-Jean Saint-Laurent, the Place des Moulins and the hill of Carmes, and on the other hand a suburban and port area outside the ramparts. A garden, surrounded on three sides by the shopping centre, has been laid out to highlight the vestiges, the results of one of the most important post-war urban excavations carried out in France. The objects discovered are on display at the Marseille History Museum.
Sources: en.wikipedia.org
Keep it in a sealed container in a cool, dry place away from direct heat and moisture. Dry powder is more stable than prepared solutions.
It can cyclize into creatinine, particularly in water or under heat. Creatinine does not support phosphocreatine energy buffering in the same way.
Laboratories commonly use chromatographic methods such as HPLC, along with spectroscopy and titration, to confirm identity and quantity. Moisture, elemental impurities, and microbial limits may also be tested.
A sealed container kept at room temperature and away from moisture is typical. Heat and humidity promote conversion to creatinine and can reduce assay values. Long-term storage under dry conditions helps maintain the original crystalline form.