HPLC assay comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-03-14. Numbers and descriptions here follow the published literature rather than marketing material.
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.
In the body, creatine is synthesized from arginine, glycine, and methionine, mainly in the liver and kidneys, and is also obtained from foods such as meat and fish. About 95% of body creatine is stored in skeletal muscle, where a fraction is phosphorylated to phosphocreatine. Phosphocreatine serves as a rapid reserve of high-energy phosphate for short bursts of ATP regeneration. The monohydrate form supplies creatine after dissolution and absorption, but it is not itself the active phosphorylated species.
Creatine was first identified in skeletal muscle extracts in the nineteenth century, and its role in phosphagen energy buffering was clarified in the twentieth century. The monohydrate salt became widely studied after methods for inexpensive synthesis and crystallization were developed. Modern research examines its effects on muscle energetics, recovery, and cognitive performance under specific conditions. Findings vary with population, exercise protocol, baseline creatine status, and measurement method. Studies often compare supplementation with placebo during controlled training or testing schedules.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | 15–25 °C | Cool, dry, sealed container; avoid heat |
| Relative humidity | Low; keep below about 60% | Moisture promotes caking and degradation |
| Primary degradation product | Creatinine | Forms by cyclization, especially in solution |
| Common assay method | HPLC with UV or RI detection | Separates creatine from creatinine and related impurities |
| Moisture content | Typically reported as percentage | Measured by Karl Fischer titration or loss on drying |
Individuals with BPD express higher levels of jealousy towards their partners in romantic relations. Manipulative behavior to obtain nurturance is considered by the DSM-IV-TR and many mental health professionals to be a characteristic of borderline personality disorder. In one research study, 88% of therapists reported that they have experienced manipulation attempts from patient(s). Marsha Linehan has argued that doing so relies upon the assumption that people with BPD who communicate intense pain, or who engage in self-harm and suicidal behavior, do so to influence the behavior of others. The impact of such behavior on others—often an intense emotional reaction in concerned friends, family members, and therapists—is thus assumed to have been the person's intention. According to Linehan, their frequent expressions of intense pain, self-harming, or suicidal behavior may instead represent a method of mood regulation or an escape mechanism from situations that feel unbearable, however, making their assumed manipulative behavior an involuntary and unintentional response.
The two substrates of this enzyme are 6-hydroxyhexanoic acid and oxidised nicotinamide adenine dinucleotide (NAD+). Its products are 6-oxohexanoic acid, reduced NADH, and a proton. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 6-hydroxyhexanoate:NAD+ oxidoreductase. This enzyme participates in caprolactam degradation.
Basophils appear in many specific kinds of inflammatory reactions, particularly those that cause allergic symptoms. Basophils contain anticoagulant heparin, which prevents blood from clotting too quickly. They also contain the vasodilator histamine, which promotes blood flow to tissues. They can be found in unusually high numbers at sites of ectoparasite infection (e.g. ticks). Like eosinophils, basophils play a role in both parasitic infections and allergies. They are found in tissues where allergic reactions are occurring and probably contribute to the severity of these reactions. Basophils have protein receptors on their cell surface that bind IgE, an immunoglobulin involved in macroparasite defense and allergy. It is the bound IgE antibody that confers a selective response of these cells to environmental substances (e.g., pollen proteins or helminth antigens). Recent studies in mice suggest that basophils may also regulate the behavior of T cells and mediate the magnitude of the secondary immune response.
Some bodybuilders inject oils or other compounds into their muscles (sometimes known as "synthol") to enhance their size or appearance. This practice can have serious health consequences and risks for humans.
Sources: en.wikipedia.org
Eumelanin (lit. 'true melanin') has two forms linked to 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI-derived eumelanin is dark brown or black and insoluble, and DHICA -derived eumelanin is lighter and soluble in alkali. Both eumelanins arise from the oxidation of tyrosine in specialized organelles called melanosomes. This reaction is catalyzed by the enzyme tyrosinase. The initial product, dopaquinone can transform into either 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI and DHICA are oxidized and then polymerize to form the two eumelanins. In natural conditions, DHI and DHICA often co-polymerize, resulting in a range of eumelanin polymers. These polymers contribute to the variety of melanin components in human skin and hair, ranging from light yellow/red pheomelanin to light brown DHICA-enriched eumelanin and dark brown or black DHI-enriched eumelanin. These final polymers differ in solubility and color. Analysis of highly pigmented (Fitzpatrick type V and VI) skin finds that DHI-eumelanin comprises the largest portion, approximately 60–70%, followed by DHICA-eumelanin at 25–35%, and pheomelanin only 2–8%. Notably, while an enrichment of DHI-eumelanin occurs in during sun tanning, it is accompanied by a decrease in DHICA-eumelanin and pheomelanin. A small amount of black eumelanin in the absence of other pigments causes grey hair. A small amount of eumelanin in the absence of other pigments causes blond hair. Eumelanin is present in the skin and hair, etc.
The Byzantine Empire distinctively blended Roman political traditions, Greek literary heritage, and Christianity, creating the civilisational framework that laid the foundation for medieval Europe. The Empire preserved European civilisation by acting as a shield against forces from Eurasian Steppe people such as the Avars, Bulgars, Cumans, Huns, Pechenegs, and Turks. The empire's legal codes significantly influenced the civil law traditions of continental Europe, Russia, Latin America, Ethiopia, and even the English-speaking common law countries; and possibly influenced Islamic legal traditions as well. It also preserved and transmitted classical learning and manuscripts, making important contributions to the intellectual revival which fuelled Italian humanism. The Byzantine Empire played a pivotal role in shaping Christianity by supporting early Church fathers and the decisions of Church councils; developing the institution of monasticism; and fostering the Orthodox tradition which continues to define much of Eastern European identity. It was also instrumental in preserving the Greek language and is credited with developing the Glagolitic alphabet, which later evolved into the Cyrillic script and Old Church Slavonic. These innovations provided the first literary language for the Slavs and formed the educational foundation for all Slavic nations.
A massive "tomato tree" in the Walt Disney World Resort's experimental greenhouses in Lake Buena Vista, Florida may have been the largest single tomato plant. It yielded a harvest of more than 32,000 tomatoes, together weighing 522 kg (1,151 lb). The town of Buñol, Spain, annually celebrates La Tomatina, a festival centered on an enormous tomato fight. On 30 August 2007, as many as 40,000 Spaniards gathered to throw 115,000 kg (254,000 lb) of tomatoes at each other in the festival. Some US states have adopted the tomato as a state fruit or vegetable. Arkansas took both sides by declaring the South Arkansas Vine Ripe Pink Tomato both the state fruit and the state vegetable in the same law, citing both its culinary and botanical classifications. In 2009, the state of Ohio passed a law making the tomato the state's official fruit, while tomato juice has been the state's official beverage since 1965. Livingston's plant breeding is commemorated in his home town of Reynoldsburg with an annual Tomato Festival; it calls itself "The Birthplace of the Tomato". In Finland, the Tomatkarnevalen is held annually in the town of Närpes. Tomatoes are sometimes thrown in public protests. Embracing it for this connotation, the Dutch Socialist party adopted the tomato as their logo. The same meaning is evoked in the name of the American review-aggregation website for film and television, "Rotten Tomatoes", though its founder mentions a scene in the 1992 movie Leolo as the immediate source of the name.
Sources: en.wikipedia.org
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.
Creatine can lose a water molecule and cyclize into creatinine, especially in aqueous solution and at elevated temperatures. This is a chemical degradation process rather than microbial spoilage.
High-performance liquid chromatography is commonly used to quantify creatine and detect creatinine. Identity can be confirmed with spectroscopy or other instrumental methods.
Creatine is the base compound, while creatine monohydrate is a solid crystalline form that contains one water molecule per creatine molecule. Once dissolved, the monohydrate dissociates and releases creatine, which can participate in cellular energy metabolism. The monohydrate is the form most commonly used in research and commercial products.