A practical reference on mass spectrometry: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-05-07 and is reviewed periodically as new material appears.
Several techniques are used for quantification. Enzymatic recycling assays rely on glutathione reductase and a colorimetric or fluorescent readout, offering sensitivity for total glutathione. High-performance liquid chromatography can separate GSH from GSSG and other thiols, often with UV, fluorescence, or electrochemical detection. Mass spectrometry provides structural confirmation and can quantify low-abundance species when paired with separation. Each approach has trade-offs in specificity, throughput, and equipment requirements, so method selection depends on the research question and available instrumentation.
Stability depends on pH, temperature, oxygen exposure, and trace metals. Aqueous solutions of reduced glutathione are susceptible to oxidation, especially when neutral or alkaline and exposed to air. Transition metal ions can catalyze thiol oxidation, so chelators and inert atmospheres are sometimes used in research settings. Standards are typically stored cold and desiccated, with limited freeze-thaw cycles. Questions remain about how closely in vitro stability data reflect the behavior of glutathione within intact cells and tissues.
Quality control for glutathione measurements includes calibration with authenticated standards, internal standards where available, blank correction, and spike recovery checks. Because glutathione can form during sample processing or degrade before analysis, pre-analytical handling is a major source of variability. Interlaboratory comparisons often show differences in reported values due to method-specific calibration and detection principles. Interpretive thresholds are context-dependent, and no single reference range applies across all tissues or matrices. Researchers generally report both reduced and oxidized forms, along with the method and sample handling details.
Quantification of glutathione in biological or food samples commonly uses liquid chromatography coupled to ultraviolet, fluorescence, electrochemical, or mass spectrometric detection. Because the thiol group oxidizes readily, samples are often acidified or derivatized immediately after collection to stabilize reduced glutathione. Enzymatic recycling assays and colorimetric kits offer higher throughput but generally lower specificity than chromatographic methods. Mass spectrometry can distinguish glutathione from related thiols and allow simultaneous measurement of oxidized forms. Reported concentrations depend strongly on sample type, extraction procedure, and analytical platform.
Glutathione reference materials are sensitive to oxygen, light, and elevated temperature. Solid material is typically stored desiccated at -20 °C or below, while solutions require tighter control because thiol oxidation proceeds faster in liquid form. Aqueous solutions are often prepared fresh, kept cold, and protected from air; some protocols add acid or chelating agents to slow metal-catalyzed oxidation. Repeated freeze-thaw cycles can accelerate degradation and should be avoided. Stability data vary by matrix, so laboratories usually verify performance with their own storage conditions.
| Property | Value | Notes |
|---|---|---|
| Reduced form | GSH | Main intracellular thiol |
| Oxidized form | GSSG | Disulfide dimer of two GSH molecules |
| Common separation method | Reversed-phase HPLC | Often with ion-pairing or derivatization |
| Typical detection | Fluorescence or mass spectrometry | UV detection is also used in some assays |
| Storage of standards | -20 °C or below, desiccated | Limit freeze-thaw and moisture exposure |
Quality control for glutathione focuses on identity, purity, and oxidation state. Certificates of analysis may report assay value, water content, and the presence of GSSG or other impurities. Chromatographic purity is often expressed as a percentage of peak area. Reference standards help laboratories compare results across instruments and batches. Because glutathione is a small, polar molecule, separation from cysteine, gamma-glutamylcysteine, and related thiols can be challenging. Verification often combines more than one analytical technique.
Measuring glutathione requires attention to sample preparation because the molecule oxidizes readily. Blood, tissue, and cell samples are often treated with acid to precipitate proteins and stabilize the thiol. Without such steps, GSH can convert to GSSG or form mixed disulfides during storage. Analytical methods include spectrophotometric assays, high-performance liquid chromatography, and mass spectrometry. Each approach has different sensitivity, specificity, and susceptibility to interference from related compounds in complex matrices.
Enzymatic recycling assays provide a complementary approach for total glutathione. In these methods, glutathione reductase reduces oxidized glutathione while a thiol-reactive reagent, such as 5,5'-dithiobis(2-nitrobenzoic acid), produces a colored product. The reaction cycles between reduced and oxidized forms, amplifying the signal. Spectrophotometric or fluorometric detection can then estimate concentration. Distinguishing reduced glutathione from glutathione disulfide often requires separate aliquots, masking agents, or chromatographic separation, and the choice affects reported values.
Storage conditions strongly influence glutathione stability. The solid reduced form is commonly kept desiccated at or below minus twenty degrees Celsius, protected from light and moisture. Aqueous solutions are less stable because the thiol group reacts with dissolved oxygen, and oxidation accelerates at neutral or alkaline pH. Acidic solutions and oxygen-free handling can slow degradation, but repeated freeze-thaw cycles should be avoided. Researchers often verify concentration before use, because apparent losses can arise from oxidation or water uptake.
Measuring glutathione in biological samples requires attention to oxidation and matrix effects. High-performance liquid chromatography with ultraviolet or fluorescence detection can separate reduced and oxidized forms after derivatization. Liquid chromatography with tandem mass spectrometry offers higher specificity and can quantify glutathione alongside related thiols. Because glutathione can oxidize during sample handling, many protocols use rapid acidification with metaphosphoric acid or sulfosalicylic acid. Internal standards help correct for losses during extraction and analysis.
=== Discovery === In 1938, Emilio Segrè and Glenn T. Seaborg isolated for the first time the metastable isotope technetium-99m, after bombarding natural molybdenum with 8 MeV deuterons in the 37-inch (940 mm) cyclotron of Ernest Orlando Lawrence's Radiation laboratory. In 1970 Seaborg explained that:
Perhaps the best-known hypothesis involving mercury and autism involves the use of the mercury-based compound thiomersal, a preservative that has been phased out from most childhood vaccinations in developed countries including the US and EU. There is no scientific evidence for a connection between thiomersal and autism, but parental concern about a relationship between thiomersal and vaccines led to decreasing rates of childhood immunizations and increasing likelihood of disease outbreaks in the 1990s. In 1999, the U.S. Public Health Service recommended that thiomersal be removed from childhood vaccines. By 2002, the flu vaccine was the only childhood vaccine using thiomersal. The removal of thiomersal did not decrease autism rates in any country that removed thiomersal from their childhood vaccines. A causal link between thiomersal and autism has been rejected by international scientific and medical professional bodies including the American Medical Association, the American Academy of Pediatrics, the American College of Medical Toxicology, the Canadian Paediatric Society, the U.S. National Academy of Sciences, the Food and Drug Administration, Centers for Disease Control and Prevention, the World Health Organization, the Public Health Agency of Canada, and the European Medicines Agency.
(2026) recover ancient DNA from mammoth ivory from the Hohle Fels cave (Germany), and report evidence of presence of mammoth specimens from multiple distinct lineages in the studied sample. Zanina et al. (2026) reconstruct the environment and diet of the woolly mammoth calf specimen "Yana" from the Batagay section (Sakha, Russia) on the basis of the study of contents of its gastrointestinal tract and the material found between its forelimbs. A new, nearly complete skeleton of a woolly mammoth, identified as a male aged approximately 30–40 years, is described from the latest Pleistocene strata from the Taymyr Peninsula (Russia) by Petrova et al. (2026). Moots et al. (2026) determine sex of 521 woolly mammoth specimens on the basis of the study of ancient DNA, reporting evidence indicating that mammoths from bone accumulation sites were predominantly female, while mammoths from other depositional settings were predominantly male, and interpret these findings as suggestive of anthropogenic origin of mammoth bone accumulations and of preferential targeting of mammoth females by humans. Hannold et al. (2026) reconstruct the diets of pygmy mammoths from Northern Channel Islands and Columbian mammoths from Rancho La Brea and coastal Santa Barbara in southern California on the basis of stable isotopes in tooth enamel. Evidence from the study of tooth enamel of Columbian mammoths from 14 sites in the Central Basin of Mexico, interpreted as indicative of a generalist diet with varying proportions of C3 and C4 plants, is presented by Rodríguez-Franco et al. (2026).
== Further reading == Baena-Cagnani CE (2001). "Desloratadine activity in concurrent seasonal allergic rhinitis and asthma". Allergy. 56 Suppl 65: 21–7. doi:10.1111/j.1398-9995.2001.00001.x-i1. PMID 11243501. Devillier P, Roche N, Faisy C (2008). "Clinical pharmacokinetics and pharmacodynamics of desloratadine, fexofenadine and levocetirizine : a comparative review". Clinical Pharmacokinetics. 47 (4): 217–30. doi:10.2165/00003088-200847040-00001. PMID 18336052. Geha RS, Meltzer EO (April 2001). "Desloratadine: A new, nonsedating, oral antihistamine". The Journal of Allergy and Clinical Immunology. 107 (4): 751–62. doi:10.1067/mai.2001.114239. PMID 11295678. Henz BM (2001). "The pharmacologic profile of desloratadine: a review". Allergy. 56 Suppl 65: 7–13. doi:10.1034/j.1398-9995.2001.00101.x. PMID 11243504.
Proper cytotrophoblast function is essential in the implantation of a blastocyst. After hatching, the embryonic pole of the blastocyst faces the uterine endometrium. Once they make contact the trophoblast begins to rapidly proliferate. The cytotrophoblast secretes proteolytic enzymes to break down the extracellular matrix between the endometrial cells to allow finger-like projections of trophoblast to penetrate through. Projections of cytotrophoblast and syncytiotrophoblast pull the embryo into the endometrium until it is fully covered by endometrial epithelium, save for the coagulation plug.
Sources: en.wikipedia.org
Iodine-131 (131I) is a beta-emitting isotope with a half-life of 8.0249 days, and comparatively energetic (0.61 MeV) beta radiation, which penetrates 0.6 to 2.0 mm from the site of uptake. This beta radiation can be used for the destruction of thyroid nodules or hyperfunctioning thyroid tissue and for elimination of remaining thyroid tissue after surgery for the treatment of Graves' disease. The purpose of this therapy, which was first explored by Dr. Saul Hertz in 1941, is to destroy thyroid tissue that could not be removed surgically. In this procedure, 131I is administered either intravenously or orally following a diagnostic scan. This procedure may also be used, with higher doses of radio-iodine, to treat patients with thyroid cancer. The 131I is taken up into thyroid tissue and concentrated there. The beta particles emitted by the radioisotope destroys the associated thyroid tissue with little damage to surrounding tissues (more than 2.0 mm from the tissues absorbing the iodine). Due to similar destruction, 131I is the iodine radioisotope used in other water-soluble iodine-labeled radiopharmaceuticals (such as MIBG) used therapeutically to destroy tissues. The high energy beta radiation (up to 606 keV) from 131I causes it to be the most carcinogenic of the iodine isotopes.
== Global demand == Global EO demand has expanded from 16.6 Mt (18.3 million short tons) in 2004 to 20 Mt (22 million short tons) in 2009, while demand for refined EO expanded from 4.64 Mt (5.11 million short tons) in 2004 to 5.6 Mt (6.2 million short tons) in 2008. In 2009, demand is estimated to have declined to about 5.2 Mt (5.7 million short tons). Total EO demand registered a growth rate of 5.6% per annum during the period 2005 to 2009 and is projected to grow at 5.7% per annum during 2009 to 2013.
Michael Rosen, (born 7 May 1946), son of Connie and Harold Rosen, is an English children's author, poet, presenter, political columnist, broadcaster, activist, and academic, who is a professor of children's literature in the Department of Educational Studies at Goldsmiths, University of London. He has written over 200 books for children and adults. Chanie Rosenberg (1922 –2021) South African-Lithuanian Jewish-born artist, author, journalist, radical pamphleteer, teacher and socialist; sister of Michael Kidron and partner of Tony Cliff, founder member of Socialist Workers Party in Britain.; relative of poet Isaac Rosenberg; studied Hebrew at Cape Town University; in 1944, moved to Palestine to live on kibbutz where she became an anti-Zionist and a revolutionary socialist and met Yigael Gluckstein (better known as Tony Cliff); moved to Britain where she was member of the Revolutionary Communist Party from 1944 to 1949; afterwards joining the group which eventually became the Socialist Workers Party; active in many anti-racist and anti-fascist mobilisations; active in the National Union of Teachers.; also artist whose sculpture has been exhibited in Royal Academy of Arts. Andrew Roth (23 April 1919 – 12 August 2010); biographer and journalist known for his compilation of Parliamentary Profiles, a directory of biographies of British Members of Parliament; compiled profiles of the personnel of the British Parliament and assessed their character traits, history, opinions and psychological drives; The Daily Telegraph called Roth a "Westminster institution".
== National differences and how to specialise == Australia In Australia, transfusion medicine is a sub-specialty of haematology. Training in transfusion medicine is covered by the Royal College of Pathologists of Australasia (RCPA). Australia has national blood services operated by the Australian Red Cross Blood Service. There are a series of guidelines and standards relevant to the laboratory released by the National Association of Testing Authorities, Australia (NATA), Australian and New Zealand Society of Blood Transfusion (ANZSBT) and RCPA. Similarly, there are a series of clinical practice, patient blood management guidelines by the National Blood Authority. In Australia, the Serious Transfusion Incident Reporting (STIR) system is in place to capture serious transfusion incidents and near-miss incidents.
In 1961, Peter Mitchell proposed chemiosmosis as a cell's primary system of energy conversion. The mechanism, now ubiquitous in living cells, powers energy conversion in micro-organisms and in the mitochondria of eukaryotes, making it a likely candidate for early life. Mitochondria produce adenosine triphosphate (ATP), the energy currency of the cell used to drive cellular processes such as chemical syntheses. The mechanism of ATP synthesis involves a closed membrane in which the ATP synthase enzyme is embedded. The energy required to release strongly bound ATP has its origin in protons that move across the membrane. In modern cells, those proton movements are caused by the pumping of ions across the membrane, maintaining an electrochemical gradient. In the first organisms, the gradient could have been provided by the difference in chemical composition between the flow from a hydrothermal vent and the surrounding seawater, or perhaps meteoric quinones that were conducive to the development of chemiosmotic energy across lipid membranes if at a terrestrial origin.
Sources: en.wikipedia.org
Common methods include enzymatic recycling assays, liquid chromatography, and mass spectrometry. Many protocols separate reduced glutathione from its oxidized disulfide form before detection.
The ratio compares reduced glutathione with its oxidized dimer. It is used as an indicator of redox status, although the value depends strongly on sample handling and analytical method.
Glutathione can oxidize quickly after a sample is collected. Acidification, cooling, and chelators are often used to reduce artifactual changes before analysis.
Acidification lowers pH and helps prevent oxidation of the thiol group during extraction and storage. It can also precipitate proteins and stabilize the reduced form before analysis.