HPLC assay raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-04-29 and is reviewed periodically as new material appears.
Commercial creatine monohydrate is typically manufactured through chemical synthesis, often starting from sarcosine and cyanamide. The resulting material is crystallized, washed, and dried to a specified hydrate content. Finished lots are tested for identity, purity, moisture, and heavy metals before release. Because the compound can cyclize to creatinine under heat or prolonged storage in solution, manufacturers control temperature and humidity during processing. The solid itself is relatively stable when kept dry and sealed, but moisture uptake can cause caking and complicate accurate assay.
Analytical laboratories commonly identify creatine monohydrate by high-performance liquid chromatography with ultraviolet detection, often after dissolving the sample in water or dilute acid. Ion-exchange or reversed-phase columns separate creatine from creatinine and related guanidino compounds. Nitrogen content can be checked by Kjeldahl or combustion methods, while moisture is measured by Karl Fischer titration or loss on drying. These techniques give complementary views: chromatographic purity addresses related substances, whereas moisture and elemental data confirm hydrate stoichiometry. No single test defines quality by itself; a combination is used in specifications.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common analytical method | HPLC-UV | Separation from creatinine and related compounds. |
| Moisture content | Typically 12% theoretical | Monohydrate stoichiometry corresponds to about 12% water by mass. |
| Typical storage temperature | 15–25 °C | Cool, dry, sealed conditions limit moisture uptake. |
| Degradation marker | Creatinine | Formed by cyclization, especially in solution or with heat. |
| Solubility class | Moderately soluble in water | Solubility rises with temperature and varies with pH. |
Creatine monohydrate is a crystalline compound formed from creatine and one water molecule in its solid lattice. Creatine itself is a nitrogen-containing organic acid involved in energy transfer in muscle and other tissues. The monohydrate form is the most common solid form used in research and commercial products because it is stable and easy to handle. The term "monohydrate" refers to the fixed one-to-one ratio of water to creatine in the crystal, not to moisture content. This distinction matters when comparing labels or calculating creatine content.
In chemical terms, creatine monohydrate is often described as N-(aminoiminomethyl)-N-methylglycine monohydrate, though nomenclature varies. Its solid state consists of zwitterionic creatine molecules linked with water through hydrogen bonding. The compound dissolves in water, but dissolution rate depends on particle size, temperature, and agitation. Once dissolved, the hydrate water becomes part of the solvent, leaving free creatine in solution. The monohydrate is not the same as creatine anhydrous, which lacks the water of crystallization and has a higher creatine fraction by mass.
Commercial creatine monohydrate is typically a white to off-white powder with low odor. It is commonly sold as a fine powder, micronized powder, or larger crystals, but these are physical forms of the same chemical. Purity grades vary, and products may contain small amounts of related substances such as creatinine, dicyandiamide, or moisture. The monohydrate is often selected for supplements and research because its production is well established and its behavior in water is predictable. Analytical certificates usually report assay, loss on drying, and heavy metals.
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 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.
Quality control of creatine monohydrate relies on a combination of identity, purity, and moisture tests. High-performance liquid chromatography with ultraviolet detection is widely used to separate creatine from creatinine and other related nitrogenous compounds. Spectroscopic methods such as infrared and nuclear magnetic resonance provide structural confirmation. Because the material is a hydrate, water content is measured separately, often by Karl Fischer titration. These tests together establish whether a lot meets a defined specification.
Manufacturing processes can leave trace amounts of dicyandiamide, creatinine, or residual solvents, depending on the synthetic route and purification steps. Heavy metals, arsenic, and microbial contamination are also monitored for food or pharmaceutical grades. Particle size distribution can affect dissolution behavior and blending uniformity, so it may be specified for certain applications. Analytical results are reported on a dry basis or as-is basis, and the difference matters when comparing certificates of analysis. Open questions remain about how minor impurities influence long-term stability under varied storage conditions.
Stability studies typically examine the effects of temperature, humidity, and light on creatine monohydrate. Sealed containers stored in cool, dry conditions help limit moisture uptake and hydrolysis. Elevated temperature and high relative humidity can accelerate conversion to creatinine, especially in aqueous solutions. In solid dosage forms, excipients and processing steps may also affect stability. Published stability data are not fully consistent across studies because test conditions and analytical methods vary.
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.
Intrathecal/intraventricular administration: Chemotherapy is injected directly into the cerebrospinal fluid, either through a lumbar puncture or a surgically implanted catheter. Intracerebral implants: A neurosurgeon creates a cavity within a tumor to allow the placement of dime-sized chemotherapy wafers, such as Gliadel wafers. Several of these wafers can be placed at the time of surgery and will release the chemotherapy agent carmustine slowly over time. This provides a much higher concentration of chemotherapy in the brain than can be obtained with intravenous administration, and it causes fewer systemic side effects. However, it is an option only for patients with surgically resectable tumours; it cannot be used to treat DIPG. Osmotic blood–brain barrier disruption (BBBD): The cells of the blood–brain barrier are shrunk by a concentrated sugar solution (mannitol). This opens the barrier and allows 10 to 100 times more chemotherapy to enter the brain. A catheter is placed into a large artery (usually the one in the groin called the femoral artery) and threaded up to the carotid or vertebral artery. The hypertonic mannitol is injected, followed by a chemotherapeutic agent. Patients spend a few days in the hospital for each administration. This has been attempted with DIPG tumours. Convection-enhanced delivery: Chemotherapy is delivered to the tumour by a surgically implanted catheter under a pressure gradient to achieve more distribution than with diffusion alone. Limited experiments have been conducted with brain tumors, including one with a DIPG.
== Mechanism == Phosphorylation involves the transfer of phosphate groups from ATP to the enzyme, the energy for which comes from hydrolysing ATP into ADP or AMP. However, dephosphorylation releases phosphates into solution as free ions, because attaching them back to ATP would require energy input. Cysteine-dependent phosphatases (CDPs) catalyse the hydrolysis of a phosphoester bond via a phospho-cysteine intermediate.
=== New Zealand === The first Pizza Hut store in New Zealand was established in New Lynn 1974 by businessman Garry Melville-Smith, who bought the franchise rights for the country. By 1990, 36 stores had been established across New Zealand. The franchise originated as a dine-in restaurant targeting families and also served alcohol, pasta, salad bars and desserts. Pizza Hut dominated the New Zealand fast food market during the 1970s, 1980s and 1990s, holding 75% of the market share at its peak. The franchise's success encouraged other fast food chains including Domino's, Eagle Boys, Pizza Haven and Hell Pizza to enter the New Zealand market. In 1996, Melville-Smith sold the New Zealand franchise back to PepsiCo, which subsequently rebranded as Restaurant Brands in 1997. In 1998, Pizza Hut shifted from a dine-in restaurant chain towards a takeaway and delivery service in response to changes in consumer behaviour. In 2000, Restaurant Brands acquired Eagle Boys' New Zealand operations, which were rebranded as Pizza Hut stores. In February 2016, the original New Lynn dine-in restaurant was demolished and replaced with a takeaway store. In late September 2024, Pizza Hut celebrated the 50th anniversary of its establishment in New Zealand by holding pop-up lunch and dinner buffet and dessert events in Auckland.
=== Typical interpretation of results === Previous treatment guidelines recommended that anyone with a viral load greater than 100,000 copies/mL of blood should begin treatment. It is now standard of care in the United States to begin anti-retroviral treatment upon discovery of HIV positive status. HIV is a retrovirus, an RNA virus that enters a host cell and uses the host DNA replication machinery and the enzyme reverse transcriptase to produce DNA from the viral RNA genome. HIV also produces an integrase enzyme which is used to integrate the newly produced viral DNA into the host's DNA. The virus is then replicated every time the host cell's DNA replicates. Due to the nature of the virus the drugs used to treat HIV are called antiretroviral medicines, and the course of treatment is called antiretroviral therapy (ART). These potent medicines cannot cure an individual; they can however manage the virus and slow the progression of the HIV infection. Strict compliance with the prescribed ART regimen is vital to controlling the disease. Highly active antiretroviral therapy (HAART) is the current recommended treatment for HIV. HAART entails taking a combination (regimen) of three or more ART medications from at least two different classes of drugs. There are six classes of ART medications:
Sources: en.wikipedia.org
Promethium is the only lanthanide and one of only two elements among the first 83 with no stable or long-lived (primordial) isotopes. This is a result of a rarely occurring effect of the liquid drop model of the nucleus and stabilities of neighbor element isotopes; it is also the least stable element of the first 84 elements. The primary decay products are neodymium and samarium isotopes (promethium-146 decays to both, the lighter isotopes generally to neodymium via positron decay and electron capture, and the heavier isotopes to samarium via beta decay). Promethium nuclear isomers may decay to other promethium isotopes and one isotope (145Pm) has a very rare alpha decay mode to stable praseodymium-141. The most stable isotope of the element is promethium-145, which has a specific activity of 139 Ci/g (5.1 TBq/g) and a half-life of 17.7 years via electron capture. Because it has 84 neutrons (two more than 82, which is a magic number corresponding to a stable neutron configuration), it may emit an alpha particle (which has 2 neutrons) to form praseodymium-141 with 82 neutrons. Thus, it is the only promethium isotope with an experimentally observed alpha decay. Its partial half-life for alpha decay is about 6.3×109 years, and the relative probability for a 145Pm nucleus to decay in this way is 2.8×10−7 %. Several other promethium isotopes such as 144Pm, 146Pm, and 147Pm also have a positive energy release for alpha decay; their alpha decays are predicted to occur but have not been observed. In total, 41 isotopes of promethium are known, ranging from 126Pm to 166Pm.
== Toxicity == Buformin was withdrawn from the market in many countries due to an elevated risk of causing lactic acidosis (although not the US, where it was never sold). Buformin is still available and prescribed in Romania (timed release Silubin Retard is sold by Zentiva), Hungary, Taiwan and Japan (sold by Nichi-Iko Pharmaceutical Co., Ltd as "DIBETOS" tablets, each containing 50 mg buformin hydrochloride). The lactic acidosis occurred only in patients with a buformin plasma level of greater than 0.60 μg/mL and was rare in patients with normal renal function. In one report, the toxic oral dose was 329 ± 30 mg/day in 24 patients who developed lactic acidosis on buformin. Another group of 24 patients on 258 ± 25 mg/day did not develop lactic acidosis on buformin.
Kefir ( kə-FEER; alternative spellings: kephir or kefier) is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. It is prepared by inoculating the milk of cows, goats, or sheep with kefir grains. Kefir is a common breakfast, lunch or dinner drink consumed in countries of West Asia and Central and Eastern Europe. Kefir is consumed at any time of the day, alongside European pastries like zelnik (zeljanica), burek and banitsa/gibanica, and is an ingredient in cold soups.
Sources: en.wikipedia.org
Three people are injured, with two hospitalised, after a gas explosion at a house in Ilford, north-east London. 11 December Urfan Sharif and Beinash Batool, the father and stepmother of 10-year-old Sara Sharif, are found guilty of her murder in August 2023. Avanti West Coast's train managers have voted to take three days of strike action over the festive period, on 22, 23 and 29 December, in an ongoing dispute about the company's "rest day working arrangements". The strikes are subsequently called off while a new offer is considered. Health Secretary Wes Streeting announces that the ban on giving puberty blockers to under-18s questioning their gender will be made permanent. The Scottish Government subsequently announces it will follow the UK by introducing a permanent ban in Scotland. It is reported that Elon Musk's Tesla car company pushed the newly elected Government of Keir Starmer to make petrol car drivers "pay more" in the days after the general election. 12 December HMS Triumph, the Royal Navy's last Trafalgar-class attack submarine, completes its final voyage before being decommissioned. 31-year-old Levi Fishlock is sentenced to nine years in prison for his part in the August riots, during which he set fire to a hotel housing asylum seekers in Rotherham. His sentence is the joint-longest of any handed down so far in relation to the disorder. 609 migrants cross the Channel in nine dinghies, the most ever on a December day since records began in 2018. This brings the total number of people crossing this year to 34,582, almost 20% more than 2023.
To fill an iatrogenic defect or cavity caused by significant tissue loss due to injury, surgical excision or debridement, which would predispose the area to postoperative seroma and/or abscess formation; To close a gaping wound that cannot be sutured directly, have difficulty healing by secondary intention and the remaining tissue is unable to support a graft; To reduce tension across the wound, which would disrupt healing and lead to excessive scarring or wound dehiscence, or; To reconstruct complex anatomic structures like breasts or jaws, as flaps may also carry over tissues such as muscles and bones that may be useful in partially restoring functions within the body region.
On 8 October 2023, a day after Hamas launched its 7 October 2023 attacks on Israel and Israel began its bombing of Gaza, Hezbollah joined the conflict in "solidarity with the Palestinians", initially firing on Israeli military outposts in Shebaa Farms and the Golan Heights—both territories under Israeli occupation. Since then, Hezbollah and Israel have been involved in cross-border military exchanges that have displaced entire communities in Israel and Lebanon, with significant damage to buildings and land along the border. From 7 October 2023 to 20 September 2024, there were 10,200 cross border attacks, of which Israel launched 8,300. Over 96,000 people in Israel, and over 111,000 in Lebanon, have been displaced during this period. Israel and Hezbollah have maintained their attacks at a level that causes harm without escalating into a full-scale war. Hezbollah has stated it will continue attacking Israel until Israel halts its operations in Gaza, where over 40,000 Palestinians had been killed. Israel demanded that Hezbollah implement UNSC 1701 and withdraw its forces north of the Litani River. Diplomatic efforts, led by U.S. envoy Amos Hochstein and France, have so far been unsuccessful in resolving the conflict. In November 2023, Israeli defense minister Yoav Gallant warned that Beirut could meet the same fate as Gaza. He made the same warning in January 2024. In June 2024, Gallant visited the United States, seeking support for an escalation of the war with Hezbollah and a possible ground invasion in Lebanon.
From 1946 through 1993, thirteen countries used ocean disposal or ocean dumping as a method to dispose of nuclear/radioactive waste with an approximation of 200,000 tons sourcing mainly from the medical, research and nuclear industry. Ocean floor disposal of radioactive waste has been suggested by the finding that deep waters in the North Atlantic Ocean do not present an exchange with shallow waters for about 140 years based on oxygen content data recorded over a period of 25 years. They include burial beneath a stable abyssal plain, burial in a subduction zone that would slowly carry the waste downward into the Earth's mantle, and burial beneath a remote natural or human-made island. While these approaches all have merit and would facilitate an international solution to the problem of disposal of radioactive waste, they would require an amendment of the Law of the Sea. Nuclear submarines have been lost and these vessels reactors must also be counted in the amount of radioactive waste deposited at sea. Article 1 (Definitions), 7., of the 1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, (the London Dumping Convention) states:
Sources: en.wikipedia.org
Laboratories typically combine chromatographic separation with moisture and elemental analysis. High-performance liquid chromatography can quantify creatine and related substances such as creatinine. Moisture methods confirm the hydrate form and help detect excess water.
The dry crystalline solid is relatively stable when protected from moisture and heat. In solution, it can convert to creatinine over time, especially at higher temperatures. Storage conditions and product form influence the rate of change.
Moisture uptake can cause particles to stick together, particularly in humid conditions or after opening a container. Clumping does not necessarily mean the creatine has degraded. It can make accurate measuring more difficult, so dry storage and sealed packaging are used.
It is a crystalline form of creatine that contains one water molecule per creatine molecule. The compound occurs naturally in muscle tissue and is also produced synthetically for research and consumer products. The monohydrate label describes the solid's hydration state.