This is a working overview of mass spectrometry, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-05 and is reviewed periodically as new material appears.
Other methods address specific purity concerns. Amino acid analysis gives compositional data after hydrolysis, while capillary electrophoresis separates by charge-to-mass ratio. Karl Fischer titration measures residual water, and gas chromatography can detect residual solvents. Nuclear magnetic resonance can identify organic impurities but is less sensitive for trace levels. No single test covers all possible impurities, so purity testing usually combines orthogonal methods and reports the conditions used. The choice of methods is guided by the impurity classes of interest.
Reverse-phase high-performance liquid chromatography (RP-HPLC) is widely used to estimate peptide purity. It separates components by hydrophobicity on a column with a water-organic mobile phase. Ultraviolet absorbance at 214 nm or 220 nm detects peptide bonds. The main peak area as a percentage of total peak area gives a purity figure. This figure depends on column, gradient, wavelength, and how peaks are integrated, so it is method-specific rather than absolute.
Mass spectrometry provides complementary information by measuring molecular mass. Electrospray ionization or matrix-assisted laser desorption/ionization can confirm the expected peptide mass and reveal related impurities with different masses. It does not directly quantify all species because ionization efficiency varies. When coupled to liquid chromatography, LC-MS can assign masses to chromatographic peaks. This helps distinguish target peptide from truncation, oxidation, or deletion products. Mass accuracy and resolution determine how confidently a mass can be matched to a proposed structure.
Handling and storage influence measured purity, and peptides can oxidize, deamidate, aggregate, or adsorb to surfaces over time. Lyophilized powders stored at -20 °C or lower are generally more stable than solutions, though some sequences require different conditions. Repeated freeze-thaw cycles can promote aggregation and loss, so testing after storage checks whether purity has changed. Stability-indicating methods compare stressed and unstressed samples to detect degradation pathways. Light exposure and pH can also accelerate modification.
Solid-phase peptide synthesis can produce truncated sequences when coupling reactions fail. Deletion peptides lack one or more internal residues, while truncation peptides end prematurely. Side reactions include aspartimide formation, oxidation of methionine, and aggregation during chain assembly. Crude synthetic peptides therefore contain target peptide plus related impurities, counterions, residual solvents, and water. Purification by preparative chromatography reduces these impurities but does not remove every closely related species, including some that differ by a single amino acid.
| Property | Value | Notes |
|---|---|---|
| Typical analytical method | RP-HPLC with UV detection | Separates by hydrophobicity; purity is method-dependent |
| Confirmatory method | LC-MS or MALDI-TOF MS | Provides molecular mass and impurity mass information |
| Common detection wavelength | 214 nm or 220 nm | Peptide bond absorbance; also 280 nm for aromatic residues |
| Typical purity specification | 95% or greater by HPLC area | Common research grade; exact threshold depends on application |
| Sample preparation | Dissolve in water/acetonitrile with acid | Formic acid or trifluoroacetic acid often used |
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.
Peptide purity testing measures how much of a sample consists of the intended peptide sequence compared with related substances, water, counterions, and residual solvents. No single analytical method captures all of these components at once. Reversed-phase high-performance liquid chromatography with ultraviolet detection is widely used because it separates peptides by hydrophobicity. The reported purity value therefore depends on the chosen method, column, mobile phase, and detection wavelength. Established practice treats purity as method-dependent rather than an absolute property of the 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.
Handling practices strongly affect measured purity and sample integrity. Many peptides are hygroscopic, susceptible to oxidation, or prone to adsorption on glass and plastic surfaces. Lyophilized powders are typically stored desiccated at -20 °C or below, while solutions may require colder storage and minimized freeze-thaw cycles. Peptides containing cysteine, methionine, or tryptophan can degrade through oxidation or disulfide exchange. Working aliquots reduce repeated exposure to moisture and temperature fluctuations during routine analysis.
Purity values do not necessarily predict biological potency. Net peptide content corrects for counterions such as acetate or trifluoroacetate, water, and residual salts. Impurity thresholds for reporting, identification, and qualification are often set according to regulatory guidance, though specific limits depend on the product class and route of administration. Open questions remain about the toxicological relevance of low-level peptide impurities and about how best to compare results across different analytical platforms. A certificate of analysis should state the methods used and the basis for each reported value.
Peptide purity testing sits within a broader quality control framework. Release testing commonly includes appearance, identity, purity, peptide content, counterion content, water content, and residual solvents. Elemental impurities and microbiological attributes may be examined when relevant to the manufacturing route. Pharmacopoeial monographs and general chapters provide methods and acceptance criteria for some peptides, but many research-grade materials are not covered by such standards. Method validation establishes specificity, linearity, accuracy, precision, range, and robustness for each test.
Basilea Pharmaceutica is a biopharmaceutical company based in Allschwil near Basel, Switzerland. Basilea was spun off from F. Hoffmann-La Roche in 2000 and has been listed as an independent company on the Swiss stock exchange since March 2004. The company's subsidiary is Basilea Pharmaceutica International AG, Allschwil, which is also based in Allschwil, Switzerland, and in which the company's operating activities are bundled.
The SpyTag/SpyCatcher system is a technology for irreversible conjugation of recombinant proteins. The peptide SpyTag (13 amino acids) spontaneously reacts with the protein SpyCatcher (12.3 kDa) to form an intermolecular isopeptide bond between the pair. DNA sequence encoding either SpyTag or SpyCatcher can be recombinantly introduced into the DNA sequence encoding a protein of interest, forming a fusion protein. These fusion proteins can be covalently linked when mixed in a reaction through the SpyTag/SpyCatcher system. Using the Tag/Catcher pair, bioconjugation can be achieved between two recombinant proteins that would otherwise be difficult or impossible with traditional direct genetic fusion between the two proteins. For example, issues regarding protein folding, suboptimal expression host, and specialized post-translational modifications may be alleviated by separating the production of the proteins with the modularity of the Tag/Catcher system.
acts as a self-standard. Ultramicroporous, microporous, and mesoporous conditions may be analyzed using this technique. Typical standard deviations for full isotherm fits including porous samples are less than 2%. Notice that in this description of physical adsorption, the entropy of adsorption is consistent with the Dubinin thermodynamic criterion, that is the entropy of adsorption from the liquid state to the adsorbed state is approximately zero.
=== Colorado === On May 17, 2024, Colorado Governor Jared Polis signed the Colorado AI Act (CAIA) into law. The CAIA establishes requirements for deployers and developers of high-risk AI systems, including transparency obligations and risk assessments, to prevent algorithmic discrimination against Colorado residents. It is the first comprehensive, state-level law that regulates high-risk AI systems in the United States. The law was unpopular among pro-business advocates. An attempt to amend the regulation failed, but its implementation was delayed from the original February 1, 2026 start date to an expected June 1, 2026 start. Jared Polis has created a committee to investigate its implementation. Brianna Titone, the bill's sponsor, criticized the commission for being full of industry representatives without representation from consumers across the state. On May 14, 2026, Polis signed into law SB 26-189, which repealed and replaced CAIA. The replacement law eliminated the focus on high-risk systems; instead, it requires companies that deploy AI for decision-making related to certain topics (like employment or housing) to inform individuals that AI is being used.
== Awards and recognition == Eberlin was named among the Forbes "30 Under 30" list in 2015. She won the Marion Milligan Mason Award of the American Association for the Advancement of Science in 2016. The award is given every two years to promising young female researchers in chemistry. She won the MacArthur "Genius" Fellowship from the John D. and Catherine T. MacArthur Foundation in 2018 for her research on the use of mass spectrometry "to differentiate more quickly and accurately diseased from healthy tissues during surgery". She is the first UT Austin professor to win MacArthur grant this century. The award consists of a $625,000 no-strings-attached grant. According to the foundation, this award goes to "extraordinarily talented and creative individuals as an investment in their potential". She also won the Moore Inventor Fellowship in 2018. She received the 2020 Curt Brunnée Award from the International Mass Spectrometry Foundation. She was named on the Power List by the Analytical Scientist in 2014, 2018, 2019, 2021, 2022, 2023, and 2024. She received the 2024 Norman Hackerman Award from the Welch Foundation and the Biemann Medal from the American Society for Mass Spectrometry in 2025.
Sources: en.wikipedia.org
Roller chains are used in low- to mid-speed drives at around 600 to 800 feet per minute; however, at higher speeds, around 2,000 to 3,000 feet per minute, V-belts are normally used due to wear and noise issues. A bicycle chain is a roller chain. Bicycle chains may have a master link, or may require a chain tool for removal and installation. A similar but larger and thus stronger chain is used on most motorcycles although it is sometimes replaced by either a toothed belt or a shaft drive, which offer lower noise level and fewer maintenance requirements. A timing chain is a roller chain used in some internal combustion automobile engines to drive a camshaft. Very high performance engines often use gear drive, and starting in the early 1960s toothed belts were used by some manufacturers.
This stirring also helps avoid the development of reductive sulfur compounds like mercaptans and hydrogen sulfide that can appear if the lees layer is more than 10 cm (3.9 in) thick and undisturbed for more than a week. Most of the benefits associated with lees contact deals with the influence on the wine of the mannoproteins released during the autolysis of the yeast cells. Composed primarily of mannose and proteins, with some glucose, mannoproteins are often bound in the cell wall of yeast with hydrophobic aroma compounds that become volatilized as the cell wall breaks down. Not only does the release of mannoproteins impart sensory changes in the wine but they can contribute to tartrate and protein stability, help enhance the body and mouthfeel of the wine as well as decrease the perception of bitterness and astringency of tannins.
Collision avoidance system – a short range radar or LIDAR system on an automobile or vehicle that detects if the vehicle is about to collide with an object and applies the brakes to prevent the collision. Radar fuze – a detonator for an aerial bomb which uses a radar altimeter to measure the height of the bomb above the ground as it falls and detonates it at a certain altitude.
=== Micelles and dendrimers === Another type of drug delivery vehicle used is polymeric micelles. They are prepared from certain amphiphilic co-polymers consisting of both hydrophilic and hydrophobic monomer units. They can be used to carry drugs that have poor solubility. This method offers little in the terms of size control or function malleability. Techniques that utilize reactive polymers along with a hydrophobic additive to produce a larger micelle that create a range of sizes have been developed. Dendrimers are also polymer-based delivery vehicles. They have a core that branches out in regular intervals to form a small, spherical, and very dense nanocarrier.
== Applications of SSMS == Spark source mass spectrometry has been used for trace analysis and multielement analysis applications for highly conducting, semiconducting, and nonconducting materials. Some examples of SSMS applications are the trace element analysis of high-purity materials, multielement analysis of elements in technical alloys, geochemical and cosmochemical samples, biological samples, industrial stream samples, and radioactive material.
Sources: en.wikipedia.org
It usually refers to the relative area of the main peak in a chromatographic separation, such as RP-HPLC. It estimates the proportion of UV-absorbing material in that peak, not the absolute mass fraction of the target peptide. Different methods can give different percentages.
HPLC separates and quantifies components, while mass spectrometry identifies molecular masses. Together they can show whether a main peak has the expected mass and whether other peaks correspond to related peptide variants. This combination is more informative than either method alone.
Higher purity reduces the proportion of detectable related impurities, which can matter for research reproducibility. However, purity value alone does not establish identity, biological activity, or safety. The appropriate purity depends on the intended use and the sensitivity of the assay.
No. Purity testing measures chemical composition and does not assess biological activity, sterility, or endotoxin levels. Functional performance must be tested in the intended assay.