A practical reference on LC-MS: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-19 and is reviewed periodically as new material appears.
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.
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.
Mass spectrometry provides complementary information about molecular identity and certain impurities. Electrospray ionization and matrix-assisted laser desorption/ionization are common ionization techniques for peptides. A measured mass close to the expected value supports correct sequence length and modifications, while extra mass signals can reveal truncations, adducts, or incomplete deprotection. Mass spectrometry alone is not a quantitative purity assay, because ionization efficiency varies between compounds. Coupling liquid chromatography to mass spectrometry links retention time with mass and helps assign peaks that ultraviolet detection records.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized peptides commonly appear as powders; color can vary with sequence. |
| Solubility class | Variable; often soluble in water or aqueous buffer | Depends on sequence, charge, and hydrophobicity. |
| Typical storage temperature | -20 °C or lower | Desiccated and protected from light; avoid repeated freeze-thaw cycles. |
| Typical analytical method | Reversed-phase HPLC with UV detection | Often paired with mass spectrometry for identity confirmation. |
| Common synonyms | Peptide purity analysis; peptide purity assay | Used in certificate of analysis and quality control contexts. |
== Kicking style == Fletcher's execution of the torpedo punt was often used as a set-play clearing strategy by coach Kevin Sheedy. In a game in 2007, he kicked a torpedo punt goal from more than 70 metres. According to The Sunday Age, it was the fifth-longest kick in the history of the VFL/AFL.
MC1R. MC1R is associated with pigmentation genetics. MC2R. MC2R is also known as the ACTH receptor or corticotropin receptor because it is specific for ACTH alone. MC3R. MC3R is associated with childhood growth, accrual of lean mass and onset of puberty. MC4R. Defects in MC4R are a cause of autosomal dominant obesity, accounting for 6% of all cases of early-onset obesity. MC5R. MC5R These receptors are inhibited by endogenous inverse agonists agouti signalling peptide and agouti-related peptide, and activated by synthetic (i.e. afamelanotide) and endogenous agonist melanocyte-stimulating hormones.
=== Climate and Health === Beginning in 2024, the HISP Centre received a grant from the Wellcome Trust to develop and pilot new DHIS2 functionalities for climate and health use cases. This has led to the development of tools for integrating weather, climate, and environmental data into DHIS2 and harmonizing it with health data and for predictive modeling of climate-sensitive diseases.
Sources: en.wikipedia.org
== Further reading == Beardsley, E. (2006). "The Spartanburg Pellagra Hospital". The South Carolina Encyclopedia. Columbia, South Carolina: University of South Carolina Press. ISBN 1-57003-598-9. Crabb, Mary Katherine (1992). "An Epidemic of Pride: Pellagra and the Culture of the American South". Anthropologica. 34 (1): 89–103. doi:10.2307/25605634. JSTOR 25605634. Hampl, J. S.; Hampl, W. S. (1 November 1997). "Pellagra and the origin of a myth: evidence from European literature and folklore". Journal of the Royal Society of Medicine. 90 (11): 636–39. doi:10.1177/014107689709001114. PMC 1296679. PMID 9496281. Hendrick, Burton J. (April 1916). "The Mastery of Pellagra: The Mysterious Disease, Almost Unknown in This Country Fifteen Years Ago, That Now Claims 7,500 Victims A Year And Is Spreading Rapidly". The World's Work: A History of Our Time. XXXI: 633–39. Kraut, Alan (3 September 2010). "Dr. Joseph Goldberger and the War on Pellagra". Office of NIH History. National Institutes of Health. Archived from the original on 22 October 2004. "Reports and Resolutions of the General Assembly of the State of South Carolina, Regular Session Commencing January 11, 1916". Annual Report of the State Board of Health (1915–1916). 4. Columbia, South Carolina: Gonzales and Bryan, state printers. 1916. Swain, C. P.; Tavill, A. S.; Neale, G. (September 1976). "Studies of tryptophan and albumin metabolism in a patient with carcinoid syndrome, pellagra, and hypoproteinemia". Gastroenterology. 71 (3): 484–89. doi:10.1016/s0016-5085(76)80460-x. PMID 133045.
In Somaliland, the Isaaq Sultanate was established in 1750. The Isaaq Sultanate was a Somali kingdom that ruled parts of the Horn of Africa during the 18th and 19th centuries. It spanned the territories of the Isaaq clan, descendants of the Banu Hashim clan, in modern-day Somaliland and Ethiopia. The sultanate was governed by the Rer Guled branch established by the first sultan, Sultan Guled Abdi, of the Eidagale clan. According to oral tradition, prior to the Guled dynasty the Isaaq clan-family were ruled by a dynasty of the Tolje'lo branch starting from, descendants of Ahmed nicknamed Tol Je'lo, the eldest son of Sheikh Ishaaq's Harari wife. There were eight Tolje'lo rulers in total, starting with Boqor Harun (Somali: Boqor Haaruun) who ruled the Isaaq Sultanate for centuries starting from the 13th century. The last Tolje'lo ruler Garad Dhuh Barar (Somali: Dhuux Baraar) was overthrown by a coalition of Isaaq clans. The once strong Tolje'lo clan were scattered and took refuge amongst the Habr Awal with whom they still mostly live. In the late 19th century, after the Berlin Conference of 1884, European powers began the Scramble for Africa. In that year, a British protectorate was declared over part of Somalia, on the African coast opposite South Yemen. Initially, this region was under the control of the Indian Office, and so administered as part of the Indian Empire; in 1898 it was transferred to control by London.
==== Australian plate ==== Lord Howe hotspot (22) 34°42′S 159°48′E, w= 0.8 az= 351° ±10° Tasmantid hotspot (39) 40°24′S 155°30′E, w= 0.8 az= 007° ±5° rate= 63 ±5 mm/yr East Australia hotspot (30) 40°48′S 146°00′E, w= 0.3 az= 000° ±15° rate= 65 ±3 mm/yr
=== Antibody-directed enzyme prodrug therapy === Antibody-directed enzyme prodrug therapy (ADEPT) involves the application of cancer-associated monoclonal antibodies that are linked to a drug-activating enzyme. Systemic administration of a non-toxic agent results in the antibody's conversion to a toxic drug, resulting in a cytotoxic effect that can be targeted at malignant cells. The clinical success of ADEPT treatments is limited.
Sources: en.wikipedia.org
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.
A single method can miss co-eluting impurities, salts, water, or structural modifications. Orthogonal techniques separate compounds by different properties, such as hydrophobicity, charge, or size. Combining results gives a more complete assessment of sample composition.
No, purity measures the amount of target relative to other peaks, not the identity or sequence of the target. Mass spectrometry and sequencing may be needed to confirm structure. A high-purity sample can still contain a peptide with an incorrect sequence.
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.