If you have been reading about HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-05-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Identity and purity are commonly assessed by high-performance liquid chromatography, often with ultraviolet detection, and by spectroscopic techniques such as infrared or nuclear magnetic resonance. These methods can distinguish creatine from creatinine and detect related impurities. Moisture content may be measured by Karl Fischer titration or loss on drying. Particle size, bulk density, and heavy metal limits are additional quality parameters. Not every product is tested by every method, so specifications depend on the intended use and regulatory framework.
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.
Several creatine forms are sold, including monohydrate, anhydrous, hydrochloride, nitrate, citrate, and blends. Once dissolved, these forms deliver creatine, but they differ in molar mass, solubility, counterions, and water content. Creatine monohydrate has the largest body of published human data among these forms. Questions remain about whether any alternative form offers meaningful advantages in absorption, tolerability, or tissue uptake under practical conditions. The hydrate form's lower creatine content by mass is a compositional fact, not a statement about effectiveness.
Creatine monohydrate is a crystalline compound formed when one molecule of creatine associates with one molecule of water in the solid lattice. Its molecular formula is C4H11N3O3, and its molar mass is about 149.15 grams per mole. The material appears as a white, odorless powder that dissolves sparingly in water at room temperature. The monohydrate designation distinguishes it from anhydrous creatine, which lacks the bound water and has a lower molar mass. This hydrate is the most common commercial form of creatine used in nutritional and research settings.
Creatine is synthesized endogenously in humans, mainly in the liver, kidney, and pancreas, from the amino acids arginine, glycine, and methionine. Skeletal muscle stores much of the body's creatine, where it participates in the phosphocreatine system that buffers adenosine triphosphate during short, intense contractions. Dietary sources include meat and fish, so omnivorous diets provide additional creatine beyond endogenous production. Supplemental creatine monohydrate supplies the same molecule found in food and tissues, not a distinct drug or hormone. Research interest centers on its role in cellular energy transfer and its effects on muscle and other tissues.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | 15–25 °C | Cool, dry, sealed conditions slow conversion to creatinine. |
| Moisture sensitivity | Moderate | Absorbs water from humid air, which can cause caking. |
| Primary purity method | HPLC-UV | Separates creatine from creatinine and related impurities. |
| Moisture method | Karl Fischer titration | Measures water content; loss on drying is an alternative. |
| Degradation product | Creatinine | Forms by dehydration, especially in solution or humid heat. |
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.
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.
In animals, creatine is synthesized mainly in liver, kidney, and pancreas from arginine, glycine, and methionine. The first committed step transfers a guanidino group from arginine to glycine, forming guanidinoacetate. Subsequent methylation by S-adenosylmethionine yields creatine. Dietary sources include meat and fish; endogenous synthesis supplies part of the body pool. Most creatine is stored in skeletal muscle, where it is converted to phosphocreatine and participates in rapid regeneration of adenosine triphosphate during short, intense activity.
Commercial creatine products appear in several forms, including monohydrate, hydrochloride, citrate, nitrate, and ethyl ester. Creatine monohydrate is the most studied form and serves as a reference material in comparative research. Different forms vary in solubility, pH, and water content, but they share creatine as the active moiety after dissolution. Claims that one form is uniformly superior remain debated, and study designs often differ in population, exercise protocol, and outcome measures. Purity and hydration state are central to interpreting product labels.
Creatine monohydrate is the hydrated form of creatine, a nitrogen-containing organic acid involved in cellular energy transfer. Its molecular formula is C4H11N3O3, and it consists of creatine plus one water molecule in the crystal lattice. The anhydrous base, creatine, has the formula C4H9N3O2. The compound appears as a white, odorless, crystalline powder and is classified as a guanidine derivative. It is distinct from creatinine, a breakdown product measured in clinical chemistry.
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.
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.
== Composition == Most hotspot volcanoes are basaltic (e.g., Hawaii, Tahiti). As a result, they are less explosive than subduction zone volcanoes, in which water is trapped under the overriding plate. Where hotspots occur in continental regions, basaltic magma rises through the continental crust, which melts to form rhyolites which can form violent eruptions. For example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when the rhyolite is completely ejected, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures (cracks in the lithosphere). An example of this activity is the Ilgachuz Range in British Columbia, which was created by an early complex series of trachyte and rhyolite eruptions, and late extrusion of a sequence of basaltic lava flows. The hotspot hypothesis is now closely linked to the mantle plume hypothesis. The detailed compositional studies now possible on hotspot basalts have allowed linkage of samples over the wider areas often implicate in the later hypothesis, and its seismic imaging developments.
A glycogen storage disease (GSD, also glycogenosis and dextrinosis) is a metabolic disorder caused by a deficiency of an enzyme or transport protein affecting glycogen synthesis, glycogen breakdown, or glucose breakdown, typically in muscles and/or liver cells. GSDs are caused by Inborn errors of carbohydrate metabolism (genetically defective enzymes or transport proteins) involved in these processes. In livestock, a defect in glycogen storage is caused by intoxication with the alkaloid castanospermine. However, not every inborn error of carbohydrate metabolism has been assigned a GSD number, even if it is known to affect the muscles or liver. For example, phosphoglycerate kinase deficiency (gene PGK1) has a myopathic form. Also, Fanconi-Bickel syndrome (gene SLC2A2) and Danon disease (gene LAMP2) were declassed as GSDs due to being defects of transport proteins rather than enzymes; however, GSD-1 subtypes b, c, and d are due to defects of transport proteins (genes SLC37A4, SLC17A3) yet are still considered GSDs. Phosphoglucomutase deficiency (gene PGM1) was declassed as a GSD due to it also affecting the formation of N-glycans; however, as it affects both glycogenolysis and glycosylation, it has been suggested that it should re-designated as GSD-XIV. Jonah Pournazarian is the most notable human with Glycogen Storage Disease (GSD). His condition has been widely covered in national and international media, and his story has drawn unprecedented awareness to GSD research.
222Rn belongs to the radium and uranium-238 decay chain, and has a half-life of 3.8235 days. Its first four products (excluding marginal decay schemes) are very short-lived, meaning that the corresponding disintegrations are indicative of the initial radon distribution. Its decay goes through the following sequence (only main decay branches shown):
: examples include water in a lake with the inlet and outlet on opposite sides and radioactive material introduced high in the stratosphere by a nuclear bomb test and filtering down to the troposphere.
He is a practising barrister and jurist and teaches course on human rights at Hebrew University of Jerusalem; author of best selling book on International Law (first published in 1977; 6th edition released in 2008); also edited Title to Territory, a collection of articles on title and sovereignty in international law. His textbook is one of the key tomes used in introductory courses on international law. Shaw has appeared before the European Court of Human Rights, European Court of Justice, the UK Supreme Court, and the International Court of Justice (ICJ). Before the ICJ, he has represented countries such as the UAE, Serbia, and Cameroon. He has represented Azerbaijan, Ukraine, Ireland, and Malaysia in front of the other courts. In January 2024, he was on the four-person team representing Israel in the case brought by South Africa in the ICJ regarding accusations of genocidal acts by Israel in Gaza in the course of the Gaza war.
Sources: en.wikipedia.org
While galectin-7 was originally identified as a gene induced by wild-type p53, which is a known tumor suppressor associated with programmed cell death, suggesting the protein being a protective function in normal cells, the p53 gene is still mutated in many cancers, losing normal function and gaining pro-tumorigenic functions. This would suggest that the mutant p53 gene induces high levels of galectin-7 gene when it was originally thought that any normal levels of galectin-7 would prevent tumors from producing.
Individual quick freezing is a descriptive term that includes all forms of freezing that is "individual" (not in a whole block) and "quick" (taking a maximum of several minutes). It may correspond to cryogenic freezing, fluidized bed freezing, or any other technique that meets the definition.
=== 1964–1988: Early work and rise to prominence === Freeman worked as a dancer at the 1964 World's Fair and was a member of the Opera Ring musical theater group in San Francisco. He acted in a touring company version of The Royal Hunt of the Sun, and also appeared as an extra in Sidney Lumet's 1965 drama film The Pawnbroker starring Rod Steiger. Between acting and dancing jobs, Freeman realized that acting was where his heart lay. "After The Royal Hunt of the Sun, my acting career just took off", he later recalled. Freeman made his Off-Broadway debut in 1967, opposite Viveca Lindfors in The Niggerlovers, a show about the Freedom Riders during the American Civil Rights Movement, before debuting on Broadway in 1968's all-black version of Hello, Dolly! that also starred Pearl Bailey and Cab Calloway. In 1969, Freeman also performed on stage in The Dozens. Beginning in 1971, Freeman starred in the PBS children's television show The Electric Company, which gave him financial stability and recognition among American audiences. His work on the show was tiring, so he quit in 1975. Television producer Joan Ganz Cooney said that Freeman loathed appearing in The Electric Company, saying "it was a very unhappy period in his life". Freeman later acknowledged that he does not think about the show, but he was grateful to have been a part of it. His first credited appearance in a feature film was in 1971's Who Says I Can't Ride a Rainbow!, a family drama starring Jack Klugman. Also that year, Freeman performed in a theater production of Purlie.
=== Cultivation === White-barked birches in particular are cultivated as ornamental trees, largely for their appearance in winter. The Himalayan birch, Betula utilis, especially the variety or subspecies jacquemontii, is among the most widely planted for this purpose. It has been cultivated since the 1870s, and many cultivars are available, including 'Doorenbos', 'Grayswood Ghost' and 'Silver Shadow'; 'Knightshayes' has a slightly weeping habit. Other species with ornamental white bark include Betula ermanii, Betula papyrifera, Betula pendula and Betula raddeana.
This increased food demand is compounded by shocks and stresses, including more frequent and intense extreme and slow-onset events due to climate change, which threaten both agricultural production – crops, livestock, aquaculture, fisheries and forestry – and the middle and downstream stages of agrifood systems. But as agrifood systems are affected by climate shocks and stresses, they are themselves a major driver of climate change.
Sources: en.wikipedia.org
Towards the late 18th century, Mathurin Jacques Brisson (1723–1806) and Comte de Buffon (1707–1788) began new works on birds. Brisson produced a six-volume work Ornithologie in 1760 and Buffon's included nine volumes (volumes 16–24) on birds Histoire naturelle des oiseaux (1770–1785) in his work on science Histoire naturelle générale et particulière (1749–1804). Jacob Temminck sponsored François Le Vaillant [1753–1824] to collect bird specimens in Southern Africa and Le Vaillant's six-volume Histoire naturelle des oiseaux d'Afrique (1796–1808) included many non-African birds. His other bird books produced in collaboration with the artist Barraband are considered among the most valuable illustrated guides ever produced. Louis Pierre Vieillot (1748–1831) spent 10 years studying North American birds and wrote the Histoire naturelle des oiseaux de l'Amerique septentrionale (1807–1808?). Vieillot pioneered in the use of life histories and habits in classification. Alexander Wilson composed a nine-volume work, American Ornithology, published 1808–1814, which is the first such record of North American birds, significantly antedating Audubon. In the early 19th century, Lewis and Clark studied and identified many birds in the western United States. John James Audubon, born in 1785, observed and painted birds in France and later in the Ohio and Mississippi valleys. From 1827 to 1838, Audubon published The Birds of America, which was engraved by Robert Havell Sr. and his son Robert Havell Jr.
Diabetes was one of the first diseases described, with an Egyptian manuscript from c. 1500 BCE mentioning "too great emptying of the urine". The Ebers papyrus includes a recommendation for a drink to take in such cases. The first described cases are believed to have been type 1 diabetes. The term "diabetes" or "to pass through" was first used in 230 BCE by the Greek Apollonius of Memphis. The disease was considered rare during the time of the Roman Empire, with Galen commenting he had seen only two cases during his career. This is possibly due to the diet and lifestyle of the people of that time, or because the clinical symptoms were only observed during the advanced stage of the disease. Galen named the disease "diarrhea of the urine" (diarrhea urinosa). Indian physicians around the sixth century CE identified the disease and classified it as madhumeha or "honey urine", noting the urine would attract ants. The earliest surviving work with a detailed reference to diabetes is that of Aretaeus of Cappadocia (2nd or early 3rd century CE). He described the symptoms and the course of the disease, which he attributed to moisture and coldness, reflecting his beliefs in the "Pneumatic School" of medicine. He hypothesized a correlation between diabetes and other diseases, and he discussed differential diagnosis from a snakebite, which also provoked excessive thirst. His work remained unknown in the West until 1552, when the first Latin edition was published in Venice.
==== Mental health ==== Estrogen is considered to play a significant role in women's mental health. Sudden estrogen withdrawal, fluctuating estrogen, and periods of sustained low estrogen levels correlate with a significant lowering of mood. Clinical recovery from postpartum, perimenopause, and postmenopause depression has been shown to be effective after levels of estrogen were stabilized and/or restored. Menstrual exacerbation (including menstrual psychosis) is typically triggered by low estrogen levels, and is often mistaken for premenstrual dysphoric disorder. Compulsions in male lab mice, such as those in obsessive-compulsive disorder (OCD), may be caused by low estrogen levels. When estrogen levels were raised through the increased activity of the enzyme aromatase in male lab mice, OCD rituals were dramatically decreased. Hypothalamic protein levels in the gene COMT are enhanced by increasing estrogen levels which are believed to return mice that displayed OCD rituals to normal activity. Aromatase deficiency is ultimately suspected which is involved in the synthesis of estrogen in humans and has therapeutic implications in humans having obsessive-compulsive disorder. Local application of estrogen in the rat hippocampus has been shown to inhibit the re-uptake of serotonin. Contrarily, local application of estrogen has been shown to block the ability of fluvoxamine to slow serotonin clearance, suggesting that the same pathways which are involved in SSRI efficacy may also be affected by components of local estrogen signaling pathways.
=== Discontinued === Acolbifene/prasterone (dehydroepiandrosterone/acolbifene; DHEA/acolbifene; prasterone/acolbifene; Femivia) – combination of acolbifene (selective estrogen receptor modulator (SERM)) and prasterone (dehydroepiandrosterone; DHEA) (androgen, other actions) – decreased libido [68] Alprostadil SEPA (prostaglandin E1 SEPA; alprostadil/soft enhancement of percutaneous absorption; Topiglan) – prostaglandin E1 (PGE1) agonist – erectile dysfunction [69] Alprostadil/lidocaine (NM02216; NM100061) – combination of alprostadil (prostaglandin E1 (PGE1) agonist) and lidocaine (sodium channel blocker, local anesthetic) – premature ejaculation [70] Amesergide (LY-237733; LY237733; LY-237,733) – serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptor antagonist, other actions – erectile dysfunction, premature ejaculation [71] Apomorphine inhalation (VR-004; VR-040; VR-400) – non-selective dopamine receptor agonist, other actions – erectile dysfunction, female sexual dysfunction [72] Apomorphine intranasal – non-selective dopamine receptor agonist, other actions – erectile dysfunction [73] Avanafil (Razatus; Spedra; Stendra; TA-1790; Zepeed) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction, premature ejaculation [74] BAY-604552 (BAY98-7081; sGC activator) – guanylate cyclase stimulant – erectile dysfunction [75] Bremelanotide (Rekynda; Vyleesi; PT-141) – melanocortin MC4 receptor agonist – erectile dysfunction [76] CP-866087 (CP-866,087) – μ-opioid receptor antagonist – female sexual dysfunction [77] DA-8031 (DA8031) – selective serotonin reuptake inhibitor (SSRI) – premature ejaculation [78] Dapoxetine (IMD dapoxetine; YHD-1044) – selective serotonin reuptake inhibitor (SSRI) – premature ejaculation [79] Delequamine (RS-15385; RS-15385197) – α2-adrenergic receptor antagonist – erectile dysfunction [80] Estradiol/testosterone transdermal (testosterone/estradiol transdermal) – combination of estradiol (estrogen) and testosterone (androgen) – female sexual dysfunction [81] GM-1485 (GPI-1485; NIL-A) – immunophilin modulator – erectile dysfunction [82] Heparin/lidocaine/sodium bicarbonate (alkalised lidocaine and heparin formulation; Hep-Lido-A compounded formulation; U-101; URG-101) – combination of heparin (Factor Xa inhibitor, thrombin inhibitor), lidocaine (sodium channel blocker, local anesthetic), and sodium bicarbonate (absorption enhancer) – dyspareunia [83] hMaxi-K gene therapy (pVAX/hSlo; URO-902) – gene transference – erectile dysfunction [84] INO-1001 (INO1001; Pardex) – poly(ADP-ribose) polymerase inhibitor – erectile dysfunction [85] LGD-2941 (LGD2941; LGD122941; LGD-122941) – selective androgen receptor modulator (SARM) – female sexual dysfunction, male sexual dysfunction [86] Melanotan II (MT-II; PT-14) – melanocortin receptor agonist – erectile dysfunction, male sexual dysfunction [87] Milnacipran (Dalcipran; F-2207; Impulsor; Ixel; Joncia; Midacipran; Midalcipran; Savella; TN-912; Toledomin) – serotonin–norepinephrine reuptake inhibitor (SNRI) – vulvodynia [88] Nitroglycerin topical (Anogesic; Cellegesic; Rectiv; Rectogesic) – nitric oxide donor – dyspareunia, vulvodynia [89] NMI-870 – α2-adrenergic receptor antagonist, nitric oxide donor – erectile dysfunction, female sexual dysfunction [90] Oxytocin (oxytocin gel; oxytocin topical; Vagitocin) – oxytocin receptor agonist – atrophic vaginitis [91] Pagoclone (IP-456; Panex; RP-62955) – GABAA receptor positive allosteric modulator and nonbenzodiazepine/cyclopyrrolone – premature ejaculation [92] PF-446687 (PF-00446687; PF-446,687) – melanocortin MC4 receptor agonist – sexual function disorders [93] PF-592379 (PF-000592379; PF-592,379) – dopamine D3 receptor agonist – erectile dysfunction [94] Research programme: therapeutics - Re-Pharm (RP-0217; RP0217) – protein phosphatase 2A (PP2A) inhibitor – sexual function disorders [95] [96] RO-0282425 (RO0282425) – melanocortin MC4 receptor agonist – erectile dysfunction [97] RTN-001 (KD-027; SLX-2101; SLx-2101) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [98] SAR-407899 (SAR407899; SAR407899A) – Rho-associated kinase inhibitor – erectile dysfunction [99] Sertraline (Aremis; Besitran; CP-51974; CP-51974-01; Gladem; J Zoloft; Lustral; Serad; Serlain; Tatig; Zoloft) – selective serotonin reuptake inhibitor (SSRI) – premature ejaculation [100] Sildenafil (Revatio; Revatio IV; UK-92480; Viagra) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction [101] Tadalafil (Adcirca; Cialis; GF-196960; IC-351; LY-450190; Zalutia) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction [102] Tadalafil sublingual (APC-8000) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [103] Tadalafil/tamsulosin (CKD-397; tamsulosin/tadalafil) – combination of tadalafil (phosphodiesterase PDE5 inhibitor) and tamsulosin (α1-adrenergic receptor antagonist) – erectile dysfunction [104] Tadalafil/tamsulosin (YBH-1603) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [105] Testosterone topical (ESP-210) – androgen (androgen receptor agonist) – female sexual dysfunction [106] Testosterone transdermal (FemTestosterone TDS) – androgen (androgen receptor agonist) – female sexual dysfunction [107] Testosterone transdermal (Luramist; testosterone MDTS; testosterone transdermal spray) – androgen (androgen receptor agonist) – female sexual dysfunction [108] TEMPE (Topical Eutectic Mixture for Premature Ejaculation) – undefined mechanism of action – premature ejaculation [109] UK-357903 (UK-357,903) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [110] UK-390957 (UK-390,957) – serotonin reuptake inhibitor (SRI) – premature ejaculation [111] UK-447841 (UK-447,841) – neprilysin inhibitor – female sexual dysfunction [112] VML-670 (VML670; CEB-1555) – serotonin 5-HT1A receptor agonist – female sexual dysfunction, male sexual dysfunction [113]
Sources: en.wikipedia.org
Solid product can remain within specification for years when stored dry and sealed, but expiration dates reflect manufacturer testing and regulatory conventions. Moisture and heat increase conversion to creatinine, so storage conditions matter more than the printed date alone. Degradation is gradual and can be monitored by purity testing.
Purity is typically evaluated by chromatographic separation with ultraviolet detection, sometimes supported by spectroscopic identity tests. Moisture and creatinine content are common quality parameters. Results depend on the analytical method, sample preparation, and specification limits.
Clumping occurs when powder absorbs moisture, causing particles to stick together. Humidity, temperature changes, and repeated container opening promote this effect. Clumps do not necessarily indicate chemical degradation, but they can affect weighing and mixing.
It is the hydrated crystalline form of creatine, containing one bound water molecule per creatine unit. The compound is commonly used as a nutritional ingredient and as a research material.