HPLC assay is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-05-11. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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 |
|---|---|---|
| Purity (typical) | ≥99% by HPLC | Supplement and pharmacopeial grades vary |
| Water content | ≈12.1% theoretical | Measured by Karl Fischer titration |
| Creatinine limit | Often ≤0.1% in pharmacopeial grade | Supplement specifications may differ |
| Storage conditions | 15–25 °C, low humidity | Away from heat and acidic environments |
| Common analytical methods | HPLC–UV, NMR, FTIR, Karl Fischer | Used for identity, assay, and water content |
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.
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.
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.
==== Films in which Jung is a character in the narrative ==== 2002 saw the release of an Italian film about Jung and Spielrein, The Soul Keeper (Prendimi l'Anima) directed by Roberto Faenza. It used English dialogue and English actors, but was never formally released in the United States. Emilia Fox played Sabina Spielrein and Iain Glen was Carl Gustav Jung. A Dangerous Method, a 2011 film directed by David Cronenberg, is a fictional dramatisation of the lives of Freud, Jung, and Sabina Spielrein between 1904 and 1913. Spielrein is the Russian woman who became Jung's lover and student and, later, an analyst herself. Michael Fassbender plays Carl Jung. The film is based on the stage play The Talking Cure by Christopher Hampton, which was in turn based on the 1993 non-fiction book by John Kerr, A Most Dangerous Method: The Story of Jung, Freud, and Sabina Spielrein. In the online animated series, Super Science Friends, Jung, voiced by Tom Park, is featured as one of the recurrent antagonists against Sigmund Freud. Soul, a 2020 Pixar film written by Pete Docter, Mike Jones and Kemp Powers, includes brief appearances of Jung as an ethereal cartoon character, "Soul Carl Jung". Jeff Lillico portrays Jung in episode 13 of season 15 "Murdoch on the Couch" (10 January 2022) of the Canadian television period detective series Murdoch Mysteries.
The photosynthetic amoeboids in the genus Paulinella—P. chromatophora, P. micropora, and marine P. longichromatophora—have the only known independently evolved chloroplast, often called a chromatophore. While all other chloroplasts originate from a single ancient endosymbiotic event, Paulinella independently acquired an endosymbiotic cyanobacterium from the genus Synechococcus around 90 – 140 million years ago. Each Paulinella cell contains one or two sausage-shaped chloroplasts; they were first described in 1894 by German biologist Robert Lauterborn. The chromatophore is highly reduced compared to its free-living cyanobacterial relatives and has limited functions. For example, it has a genome of about 1 million base pairs, one third the size of Synechococcus genomes, and only encodes around 850 proteins. However, this is still much larger than other chloroplast genomes, which are typically around 150,000 base pairs. Chromatophores have also transferred much less of their DNA to the nucleus of their hosts. About 0.3–0.8% of the nuclear DNA in Paulinella is from the chromatophore, compared with 11–14% from the chloroplast in plants. Similar to other chloroplasts, Paulinella provides specific proteins to the chromatophore using a specific targeting sequence. Because chromatophores are much younger compared to the canonical chloroplasts, Paulinella chromatophora is studied to understand how early chloroplasts evolved.
About 100,000 protesters occupied Piața Operei (Opera Square – today Piața Victoriei, Victory Square) and chanted anti-government slogans: "Noi suntem poporul!" ("We are the people!"), "Armata e cu noi!" ("The army is on our side!"), "Nu vă fie frică, Ceaușescu pică!" ("Have no fear, Ceaușescu is falling!") Meanwhile, Secretary to the Central Committee Emil Bobu and Prime Minister Constantin Dăscălescu were sent by Elena Ceaușescu (Nicolae being at that time in Iran) to resolve the situation. They met with a delegation of the protesters and agreed to free the majority of the arrested protesters. However, they refused to comply with the protesters' main demand— the resignation of Ceaușescu—and the situation remained essentially unchanged. The next day, trains loaded with workers from factories in Oltenia arrived in Timișoara. The regime was attempting to use them to repress the mass protests, but after a brief encounter they ended up joining the protests. One worker explained, "Yesterday our factory boss and a party official rounded us up in the yard, handed us wooden clubs and told us that Hungarians and 'hooligans' were devastating Timișoara and that it is our duty to go there and help crush the riots.
=== Portion size irregularities === Some customers took to the social media platform TikTok accusing Chipotle of reducing portion sizes. In June 2024, a Wells Fargo analyst and his team set investigated the matter and ordered 75 identically configured items from 8 different Chipotle locations in New York City. The team weighed each bowl and reported that portion sizes varied widely, ranging from 14 to 27 ounces (400 to 770 g) with a median weight of 21.5 ounces (610 g).
=== Creation of Animal Models === Intracerebroventricular injection has been used to inject drugs that induce a diseased state to create animal models for a variety of diseases. Of these, Alzheimer's disease (AD) animal models are heavily represented in the literature. ICV injection of Streptozotocin has been used to create a metabolic model of Alzheimer's disease. This protocol works by damaging the control level of cerebral glucose metabolism to mimic Alzheimer's disease symptoms. An early sign of AD is glucose hypometabolism and impaired insulin signaling has been seen in AD patients. Streptozotocin has also largely been used to create diabetes animal models, by injecting either intravenously or intraperitoneally. These ICV injections result in models for the sporadic Alzheimer's disease (sAD) form, rather than familial. A characteristic of sAD is an insulin-resistant brain state (IRBS). Streptozotocin is a beta-cytotoxic drug and by injecting it directly into the cerebral ventricles, the treated mice develop symptoms that align with sAD symptoms in humans. Some of these symptoms include IRBS-associated memory impairment, glucose hypometabolism, oxidative stress, and neurodegeneration. More recently, a model for AD that represents both familial and sporadic AD has emerged. In the clinic, as well as independent experiments, an increase in amyloid beta (Aβ) levels in the brain has been seen to cause Alzheimer-like symptoms. To create an animal model of AD, Aβ can be injected using ICV injection.
Sources: en.wikipedia.org
N-terminal prohormone of brain natriuretic peptide (NT-proBNP or BNPT) is a 76 amino acid long protein that is cleaved from the N-terminal end of the 108 amino acid long prohormone proBNP to release brain natriuretic peptide 32 (BNP, also known as B-type natriuretic peptide). The human version consists of residue number 27–102 of preproBNP the product of the NPPB gene. Both BNP and NT-proBNP levels in the blood are used for screening, diagnosis of acute congestive heart failure (CHF) and may be useful to establish prognosis in heart failure, as both markers are typically higher in patients with worse outcome. The plasma concentrations of both BNP and NT-proBNP are also typically increased in patients with asymptomatic or symptomatic left ventricular dysfunction and is associated with coronary artery disease, myocardial ischemia, and severity of aortic valve stenosis.
The mathematics of the preadaptation model assume that the distribution of fitness effects is bimodal, with new sequences of mutations tending to break something or tinker, but rarely in between. Following this logic, populations may either evolve local solutions, in which selection operates on each individual locus and a relatively high error rate is maintained, or a global solution with a low error rate which permits the accumulation of deleterious cryptic sequences. De novo gene birth is thought to be favored in populations that evolve local solutions, as the relatively high error rate will result in a pool of cryptic variation that is "preadapted" through the purging of deleterious sequences. Local solutions are more likely in populations with a high effective population size. In support of the preadaptation model, an analysis of ISD in mice and yeast found that young genes have higher ISD than old genes, while random non-genic sequences tend to show the lowest levels of ISD. Although the observed trend may have partly resulted from a subset of young genes derived by overprinting, higher ISD in young genes is also seen among overlapping viral gene pairs. With respect to other predicted structural features such as β-strand content and aggregation propensity, the peptides encoded by proto-genes are similar to non-genic sequences and categorically distinct from canonical genes.
The breast-filler fat was harvested by liposuction (abdomen, buttocks, thighs), and yielded fat-graft volumes of 220–650 cm3 per breast. At six months post-procedure, the follow-up treatment included photographs, intravenous contrast MRI or 3-D volumetric imaging, or both. Each woman had an increased breast volume of 250 cm3 per breast, a mean volume increase confirmed by quantitative MRI analysis. The mean increase in breast volume was 1.2 times the initial breast volume measurements; the statistical difference between the pre-procedure and the six-month post-procedure breast volumes was (P< 00.0000007); the percentage increase basis of the breast volume was 60–80% of the initial, pre-procedure breast volume.
=== Media and arts representation of sickle cell disease === Popular media and art have been important educational tools about sickle cell disease. Hertz Nazaire was a Haitian-American visual artist, writer, and advocate who lived with sickle cell disease and used his art to raise awareness, combat stigma, and champion better access to care. Representations of sickle cell disease in television shows include in the longrunning American medical drama ER (season 4 "Obstruction of Justice" and season 15 "Separation Anxiety" and "Dream Runner"), the 2024 British superhero series Supacell, in the 2024 period drama Lady in the Lake, and in the 2025 medical procedural drama The Pitt (episode "8:00 am"). Noah Wyle, who plays Dr. Michael "Robby" Robinavitch on The Pitt, has spoken about the importance of popular media representation of sickle cell and the impacts of racism on the quality of care patients receive. Sickle cell disease has also been featured in several movies including the 1973 Sydney Poitier classic, A Warm December, 1996 Nigerian drama Mortal Inheritance, Genie Award- winning 2008 Canadian drama Nurse.Fighter.Boy, the 2017 animated documentary Spilled Milk, the 2020 Nigerian drama Strain, the 2022 animated short The Park Bench, and the 2023 American sci-fi action film Transformers: Rise of the Beasts.
20 standard amino acids 22 proteinogenic amino acids over 80 amino acids created abiotically in high concentrations about 900 are produced by natural pathways over 118 engineered amino acids have been placed into proteins These groups overlap, but are not identical. All 22 proteinogenic amino acids are biosynthesised by organisms and some, but not all, of them also are abiotic (found in prebiotic experiments and meteorites). Some natural amino acids, such as norleucine, are misincorporated translationally into proteins due to infidelity of the protein-synthesis process. Many amino acids, such as ornithine, are metabolic intermediates produced biosynthetically, but not incorporated translationally into proteins. Post-translational modification of amino acid residues in proteins leads to the formation of many proteinaceous, but non-proteinogenic, amino acids. Other amino acids are solely found in abiotic mixes (e.g. α-methylnorvaline). Over 30 unnatural amino acids have been inserted translationally into proteins in engineered systems, yet are not biosynthetic.
Sources: en.wikipedia.org
==== Tax expenditures ==== The term "tax expenditures" refers to income exclusions, deductions, preferential rates, and credits that reduce revenues for any given level of tax rates in the individual, payroll, and corporate income tax systems. Like conventional spending, they contribute to the federal budget deficit. They also influence choices about working, saving, and investing, and affect the distribution of income. The amount of reduced federal revenues are significant, estimated by CBO at nearly 8% GDP or about $1.5 trillion in 2017, for scale roughly half the revenue collected by the government and nearly three times as large as the budget deficit. Since eliminating a tax expenditure changes economic behavior, the amount of additional revenue that would be generated is somewhat less than the estimated size of the tax expenditure. CBO reported that the following were among the largest individual (non-corporate) tax expenditures in 2013:
The quantitative "reading" is usually based on detection of intensity of transmitted light by spectrophotometry, which involves quantitation of transmission of some specific wavelength of light through the liquid (as well as the transparent bottom of the well in the multiple-well plate format). The sensitivity of detection depends on amplification of the signal during the analytic reactions. Since enzyme reactions are very well known amplification processes, the signal is generated by enzymes which are linked to the detection reagents in fixed proportions to allow accurate quantification, and thus the name "enzyme-linked". The analyte is also called the ligand because it will specifically bind or ligate to a detection reagent, thus ELISA falls under the bigger category of ligand binding assays. The ligand-specific binding reagent is "immobilized", i.e., usually coated and dried onto the transparent bottom and sometimes also side wall of a well (the stationary "solid phase"/"solid substrate" here as opposed to solid microparticle/beads that can be washed away), which is usually constructed as a multiple-well plate known as the "ELISA plate". Conventionally, like other forms of immunoassays, the specificity of antigen-antibody type reaction is used because it is easy to raise an antibody specifically against an antigen in bulk as a reagent. Alternatively, if the analyte itself is an antibody, its target antigen can be used as the binding reagent.
Lawsone (2-hydroxy-1,4-naphthoquinone), also known as hennotannic acid, is a red-orange dye present in the leaves of the henna plant (Lawsonia inermis), for which it is named, as well as in the common walnut (Juglans regia) and water hyacinth (Pontederia crassipes). Humans have used henna extracts containing lawsone as hair and skin dyes for more than 5,000 years. Lawsone reacts chemically with the protein keratin in skin and hair via a Michael addition reaction, resulting in a strong permanent stain that lasts until the skin or hair is shed. Darker colored staining is due to more lawsone–keratin interactions occurring, which evidently break down as the concentration of lawsone decreases and the tattoo fades. Lawsone strongly absorbs UV light, and aqueous extracts can be effective sunless tanning agents and sunscreens. Lawsone is a 1,4-naphthoquinone derivative, an analog of hydroxyquinone containing one additional ring. Lawsone isolation from Lawsonia inermis can be difficult due to its easily biodegradable nature. Isolation involves four steps:
The discovery of an orally inactive peptide from the skin of poisonous frogs established the important role of angiotensin converting enzyme (ACE) inhibitors in regulating blood pressure. This led to the development of captopril, the first ACE inhibitor. When the adverse effects of captopril became apparent new derivates were designed. Then after the discovery of two active sites of ACE: N-domain and C-domain, the development of domain-specific ACE inhibitors began.
== Nullification == Tensions arose between the Malian government and the Permanent Strategic Framework for Peace, Security, and Development (CSP-PSD), a coalition of the CMA and pro-government militias, in August 2023 following the Malian government and allied Wagner Group's atrocities against civilians. The conflict culminated on August 11, 2023, when CSP-PSD fighters clashed with Mali and Wagner over control of the former MINUSMA base in Ber, which MINUSMA hadn't even finished evacuating. This conflict spiraled into a war between the CSP-PSD and the Malian government, and the nullification of the Algiers Agreement. The Malian government announced its withdrawal from the agreement on January 25, 2024. The government cited the failure of other parties, including Algeria, to uphold the terms of the agreement. Mali's transitional government also accused Algeria of "unfriendly acts" and instrumentalising the accord for its own interests. The Malian authorities further alleged that certain groups, formerly involved in the peace process, had transformed into "terrorist actors" with ties to Algeria.
Sources: en.wikipedia.org
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.
Creatinine is a degradation product formed when creatine loses water and cyclizes. It can appear during storage, processing, or analysis if conditions are harsh. Quality specifications often set a maximum limit for creatinine to control purity.
No universal testing protocol applies across all markets. Some products follow pharmacopeial monographs, while others rely on manufacturer specifications and third-party certificates. Common tests include assay, water content, heavy metals, and microbial 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.