The short version of RP-HPLC fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-08-19 and is reviewed periodically as new material appears.
Orthogonal separation methods address impurities that RP-HPLC may not resolve. Size-exclusion chromatography detects aggregates and higher-order species, while ion-exchange chromatography separates charge variants. Capillary electrophoresis can assess charge-to-mass ratios and, in some formats, size-based impurities. Amino acid analysis and nitrogen determination estimate peptide content rather than chromatographic purity. Because each technique has a different selectivity, a complete purity profile usually combines results from more than one method. The choice of method depends on the impurity classes of concern.
Reversed-phase high-performance liquid chromatography (RP-HPLC) is widely used to estimate peptide purity. Separation depends on interactions between peptide residues and a hydrophobic stationary phase, with gradients of water and organic solvent. Ultraviolet detection near 214 nm responds to the peptide backbone and to many related impurities. The resulting chromatogram is often expressed as area percent, which reports the proportion of peak area assigned to the main component. Different columns, gradients, and wavelengths can produce different purity values for the same material.
Chromatographic separation resolves truncated, oxidized, deamidated, and epimerized peptide variants when their retention times differ from the target. Mass spectrometry confirms molecular mass and can reveal modifications that UV detection misses. Liquid chromatography coupled to mass spectrometry combines separation with identity information, which helps distinguish a pure target from a co-eluting impurity. UV-based area percent can overestimate purity if an impurity lacks a chromophore or if the target and impurity have similar response factors. Researchers often report both chromatographic purity and mass confirmation to give a fuller picture.
Additional techniques address components that reversed-phase chromatography may not resolve. Ion-exchange chromatography separates by charge, size-exclusion chromatography detects aggregates, and capillary electrophoresis offers high separation efficiency. Water content is measured by Karl Fischer titration, residual solvents by gas chromatography, and elemental impurities by inductively coupled plasma mass spectrometry. Amino acid analysis or nitrogen determination can estimate peptide content on a mass basis. Purity is frequently reported as area percent, yet standardized comparison across laboratories remains an open question because methods and reporting practices differ.
| Property | Value | Notes |
|---|---|---|
| Common separation technique | Reversed-phase HPLC | Separates mainly by hydrophobicity; gradient elution is typical. |
| Typical detection wavelength | 214 nm | Peptide bond absorbance; also detects many organic impurities. |
| Identity confirmation method | LC-MS or MALDI-MS | Provides molecular mass; not a stand-alone quantitative purity measure. |
| Aggregate assessment method | Size-exclusion chromatography | Detects dimers, oligomers, and larger species. |
| Content assessment method | Amino acid analysis | Estimates peptide mass fraction after hydrolysis and separation. |
== Units of measurement == When referring to dietary allowances or nutritional science, retinol is usually measured in international units (IU). IU refers to biological activity and therefore is unique to each individual compound, however, 1 IU of retinol is equivalent to approximately 0.3 micrograms (300 nanograms).
Glucagon-like peptide-2 (GLP-2) is a 33 amino acid peptide with the sequence HADGSFSDEMNTILDNLAARDFINWLIQTKITD (see Proteinogenic amino acid) in humans. GLP-2 is created by specific post-translational proteolytic cleavage of proglucagon in a process that also liberates the related glucagon-like peptide-1 (GLP-1). GLP-2 is produced by the intestinal endocrine L cell and by various neurons in the central nervous system. Intestinal GLP-2 is co-secreted along with GLP-1 upon nutrient ingestion. When externally administered, GLP-2 produces a number of effects in humans and rodents, including intestinal growth, enhancement of intestinal function, reduction in bone breakdown and neuroprotection. GLP-2 may act in an endocrine fashion to link intestinal growth and metabolism with nutrient intake. GLP-2 and related analogs (such as Teduglutide) may be treatments for short bowel syndrome, Crohn's disease, osteoporosis and as adjuvant therapy during cancer chemotherapy. GLP-2 has an antidepressant effect in a mouse model of depression when delivered via intracerebroventricular injection. However, a GLP-2 derivative (PAS-CPP-GLP-2) was shown to be efficiently delivered to the brain intranasally, with similar efficacy.
== Other uses == Gallantry Cross, Gold of the Republic of Venda Geological Curators' Group, a UK charity promoting geology Global Church of God, a Sabbatarian church based in England Government College Gujranwala, in Pakistan The Grilled Cheese Grill, an American restaurant chain Guardian Capital Group, a Canadian financial services company Gwaun-Cae-Gurwen, a village in Neath Port Talbot, Wales Knight Grand Cross of the Royal Guelphic Order, a Hanoverian order of chivalry
Expansion of the bone marrow in the developing child leads to a distinctive facial shape often referred to as "Chipmunk facies". Other skeletal changes include osteoporosis, growth retardation, and malformation of the spine. People with thalassemia can get too much iron in their bodies, either from the disease itself as RBCs are destroyed, or as a consequence of frequent blood transfusions. Excess iron is not excreted, but forms toxic non-transferrin-bound iron. This can lead to organ damage, potentially affecting the heart, liver, endocrine system, bones and spleen. Symptoms include an irregular heartbeat, cardiomyopathy, cirrhosis of the liver, hypothyroidism, delayed puberty and fertility problems, brittle and deformed bones, and an enlarged spleen. The spleen is the organ which removes damaged red blood cells from circulation; in thalassemia patients it is abnormally active, causing it to enlarge and possibly become hyperactive, a condition called hypersplenism. The immune system can become compromised in a number of ways; anemia, iron overload, and hypersplenism may affect the immune response and increase the risk of severe infection.
Sources: en.wikipedia.org
(Rateable Values) (Scotland) Order 1993 (S.I. 1993/878) British Gas plc. (Rateable Values) (Scotland) Order 1993 (S.I. 1993/879) British Railways Board (Rateable Values) (Scotland) Order 1993 (S.I. 1993/880) British Telecommunications plc. (Rateable Values) (Scotland) Order 1993 (S.I. 1993/881) Glasgow Underground (Rateable Values) (Scotland) Order 1993 (S.I. 1993/882) Lochaber Power Company (Rateable Values) (Scotland) Order 1993 (S.I. 1993/883) Mercury Communications Ltd. (Rateable Values) (Scotland) Order 1993 (S.I. 1993/884) Mines and Quarries (Rateable Values) (Scotland) Order 1993 (S.I. 1993/885) Water Undertakings (Rateable Values) (Scotland) Order 1993 (S.I. 1993/886) National Health Service Act 1977 (Composition of Medical Practices Committee) Modification Order 1993 (S.I. 1993/887) A1 Trunk Road (Islington) Red Route Traffic Order 1993 (S.I. 1993/891) United Kingdom Central Council for Nursing, Midwifery and Health Visiting (Legal Assessors) (Amendment) Order 1993 (S.I. 1993/892) Nurses, Midwives and Health Visitors (Professional Conduct) Rules 1993 Approval Order 1993 (S.I. 1993/893) Non-Domestic Rating (Collection and Enforcement) (Amendment and Miscellaneous Provision) (No. 2) Regulations 1993 (S.I. 1993/894) A1 Trunk Road (Islington) (Bus Lanes) Red Route Traffic Order 1993 (S.I. 1993/895) A1 Trunk Road (Haringey) Red Route Traffic Order 1993 (S.I. 1993/896) A1 Trunk Road (Haringey) (Bus Lanes) Red Route Traffic Order 1993 (S.I. 1993/897) Act of Sederunt (Fees of Solicitors in the Sheriff Court) (Amendment) 1993 (S.I.
=== Other === In traditional Japanese art, alum and animal glue were dissolved in water, forming a liquid known as dousa (ja:礬水), and used as an undercoat for paper sizing. Alum is an ingredient in some recipes for homemade modeling compounds, often called "play clay" or "play dough", intended for use by children. Potassium alum was formerly used as a hardener for photographic emulsions (films and papers), usually as part of the fixer. It has now been replaced in that use by other chemicals.
=== General features === Some general architectural features of the ribosome are conserved across kingdoms: The structure of the small subunit can be sub-divided into two large segments, the head and the body. Characteristic features of the body include the left and right feet, the shoulder and the platform. The head features a pointed protrusion reminiscent of a bird's beak. In the characteristic "crown view" of the large subunit, structural landmarks include the central protuberance, the L1-stalk and the P-stalk. The majority of the eukaryote-specific RNA and protein elements are found on the solvent-exposed sides of the 40S and 60S subunits. The subunit interface, as well as important functional regions such as the peptidyl transferase center and the decoding site are mostly conserved, with some differences observed in the surrounding regions. In stark contrast to prokaryotic ribosomal proteins, which interact primarily with RNA, the eukaryote-specific protein segments engage in a multitude of protein-protein interactions. Long-distance interactions are mediated by eukaryote-specific helical extensions of ribosomal proteins, and several eukaryotic ribosomal proteins jointly to form inter-protein beta-sheets.
Sources: en.wikipedia.org
Temperature-responsive polymers or thermoresponsive polymers are polymers that exhibit drastic and discontinuous changes in their physical properties with temperature. The term is commonly used when the property concerned is solubility in a given solvent, but it may also be used when other properties are affected. Thermoresponsive polymers belong to the class of stimuli-responsive materials, in contrast to temperature-sensitive (for short, thermosensitive) materials, which change their properties continuously with environmental conditions. In a stricter sense, thermoresponsive polymers display a miscibility gap in their temperature-composition diagram. Depending on whether the miscibility gap is found at high or low temperatures, either an upper critical solution temperature (UCST) or a lower critical solution temperature (LCST) exists.
Removal of a proton from an aliphatic –OH group is difficult to achieve in aqueous solution because the energy required for this process is rather large. Thus, ionization of aliphatic –OH groups occurs in aqueous solution only in special circumstances. One such circumstance is found with compounds containing the H2N–C–C–OH substructure. For example, compounds containing the 2-aminoethanol substructure can form metal–chelate complexes with the deprotonated form, H2N–C–C–O−. The chelate effect supplies the extra energy needed to break the O–H bond. An important example occurs with the molecule tris. This molecule should be used with caution as a buffering agent as it will form chelate complexes with ions such as Fe3+ and Cu2+.
== Actions == Due to their modulatory and diffusive nature, neuropeptides can act on multiple time and spatial scales. A nearly complete map of these interactions is known for at least one small animal, C. elegans. For many other animals, at least some neuropeptide actions are known, as shown in the Examples section above.
=== Liver === The liver parenchyma is the functional tissue of the organ made up of around 80% of the liver volume as hepatocytes. The other main type of liver cells are non-parenchymal. Non-parenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume.
Sources: en.wikipedia.org
RP-HPLC purity is the relative area of the main peptide peak compared with the total integrated peak area. It reflects ultraviolet-absorbing species under one set of separation conditions. It does not identify every impurity or measure biological activity.
Chromatographic conditions such as column chemistry, gradient slope, mobile-phase additives, and detection wavelength affect peak resolution. Sample preparation and integration rules also influence area percent values. Without a shared reference standard and validated method, direct comparisons remain uncertain.
Purity describes the proportion of the main peak among detected components. Peptide content measures the amount of the target peptide in a sample after accounting for counterions, water, and residual salts. A sample can have high chromatographic purity but lower net peptide content.
It usually refers to the relative peak area of the target peptide in a chromatogram, not the mass fraction of the entire sample. Different analytical methods can yield different purity values. Water, counterions, and residual solvents are excluded unless the calculation specifies otherwise.