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101-401: A mass spectrum is a type of plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules , and to elucidate the chemical identity or structure of molecules and other chemical compounds . In a typical MS procedure, a sample, which may be solid, liquid, or gaseous,

202-485: A mass spectrum , a record of ions as a function of m/Q . Typically, some type of electron multiplier is used, though other detectors including Faraday cups and ion-to-photon detectors are also used. Because the number of ions leaving the mass analyzer at a particular instant is typically quite small, considerable amplification is often necessary to get a signal. Microchannel plate detectors are commonly used in modern commercial instruments. In FTMS and Orbitraps ,

303-400: A broad application, in practice have come instead to connote a specific or a limited number of instrument configurations. An example of this is isotope-ratio mass spectrometry (IRMS), which refers in practice to the use of a limited number of sector based mass analyzers; this name is used to refer to both the application and the instrument used for the application. An important enhancement to

404-443: A central, spindle shaped electrode. The electrode confines the ions so that they both orbit around the central electrode and oscillate back and forth along the central electrode's long axis. This oscillation generates an image current in the detector plates which is recorded by the instrument. The frequencies of these image currents depend on the mass-to-charge ratios of the ions. Mass spectra are obtained by Fourier transformation of

505-429: A characteristic fragmentation pattern. In 1886, Eugen Goldstein observed rays in gas discharges under low pressure that traveled away from the anode and through channels in a perforated cathode , opposite to the direction of negatively charged cathode rays (which travel from cathode to anode). Goldstein called these positively charged anode rays "Kanalstrahlen"; the standard translation of this term into English

606-532: A chronological record of temperature and salinity of the water in the area. The oxygen isotope ratio in the atmosphere varies predictably with time of year and geographic location; e.g. there is a 2% difference between O-rich precipitation in Montana and O-depleted precipitation in Florida Keys. This variability can be used for approximate determination of geographic location of origin of a material; e.g. it

707-414: A mass filter, to transmit a particular fragment ion to the detector. If a quadrupole is made to rapidly and repetitively cycle through a range of mass filter settings, full spectra can be reported. Likewise, a triple quad can be made to perform various scan types characteristic of tandem mass spectrometry . The quadrupole ion trap works on the same physical principles as the quadrupole mass analyzer, but

808-775: A mass spectrometer. A collision cell then stabilizes the peptide ions while they collide with a gas, causing them to fragment by collision-induced dissociation (CID). A further mass analyzer then sorts the fragments produced from the peptides. Tandem MS can also be done in a single mass analyzer over time, as in a quadrupole ion trap . There are various methods for fragmenting molecules for tandem MS, including collision-induced dissociation (CID), electron capture dissociation (ECD), electron transfer dissociation (ETD), infrared multiphoton dissociation (IRMPD), blackbody infrared radiative dissociation (BIRD), electron-detachment dissociation (EDD) and surface-induced dissociation (SID). An important application using tandem mass spectrometry

909-471: A natural abundance of about 25 percent). The analyzer part of the spectrometer contains electric and magnetic fields, which exert forces on ions traveling through these fields. The speed of a charged particle may be increased or decreased while passing through the electric field, and its direction may be altered by the magnetic field. The magnitude of the deflection of the moving ion's trajectory depends on its mass-to-charge ratio. Lighter ions are deflected by

1010-453: A nuclear fission reaction. While the latter is almost as universally due to human influence as the former two, the natural nuclear fission reactor at Oklo , Gabon was detected through a significant diversion of U concentration in samples from Oklo compared to those of all other known deposits on earth. Given that U is a material of proliferation concern then as now every IAEA -approved supplier of Uranium fuel keeps track of

1111-519: A phosphor screen was replaced by indirect measurements with an oscilloscope . The use of the term mass spectroscopy is now discouraged due to the possibility of confusion with light spectroscopy . Mass spectrometry is often abbreviated as mass-spec or simply as MS . Modern techniques of mass spectrometry were devised by Arthur Jeffrey Dempster and F.W. Aston in 1918 and 1919 respectively. Sector mass spectrometers known as calutrons were developed by Ernest O. Lawrence and used for separating

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1212-434: A range of m/z to catalog the ions present. The time-of-flight (TOF) analyzer uses an electric field to accelerate the ions through the same potential , and then measures the time they take to reach the detector. If the particles all have the same charge , their kinetic energies will be identical, and their velocities will depend only on their masses . For example, ions with a lower mass will travel faster, reaching

1313-419: A relatively constant isotope ratio in all natural samples with ~0.72% U , some 55  ppm U (in secular equilibrium with its parent nuclide U ), and the balance made up by U . Isotopic compositions that diverge significantly from those values are evidence for the uranium having been subject to depletion or enrichment in some fashion or of (part of it) having participated in

1414-413: A static electric and/or magnetic field to affect the path and/or velocity of the charged particles in some way. As shown above, sector instruments bend the trajectories of the ions as they pass through the mass analyzer, according to their mass-to-charge ratios, deflecting the more charged and faster-moving, lighter ions more. The analyzer can be used to select a narrow range of m/z or to scan through

1515-603: A team that took the first photo of a single atom. He continued work on ion traps at the University of Washington , until his retirement in October 2002. In May 2010, he was honoured as one of Washington's Nobel laureates by Crown Princess Victoria of Sweden at a special event in Seattle. He was married to Irmgard Lassow, now deceased, and the couple had a son, Gerd, also deceased. In 1989 Dehmelt married Diana Dundore,

1616-548: A very redox-active element, sulfur can be useful for recording major chemistry-altering events throughout Earth's history , such as marine evaporites which reflect the change in the atmosphere's redox state brought about by the Oxygen Crisis . Lead consists of four stable isotopes : Pb, Pb, Pb, and Pb. Local variations in uranium / thorium / lead content cause a wide location-specific variation of isotopic ratios for lead from different localities. Lead emitted to

1717-460: A wide array of sample types. In this source, a plasma that is electrically neutral overall, but that has had a substantial fraction of its atoms ionized by high temperature, is used to atomize introduced sample molecules and to further strip the outer electrons from those atoms. The plasma is usually generated from argon gas, since the first ionization energy of argon atoms is higher than the first of any other elements except He, F and Ne, but lower than

1818-510: Is C-depleted. The layer of limestone deposited at the Permian extinction 252 Mya can be identified by the 1% drop in C/ C. The C isotope is important in distinguishing biosynthetized materials from man-made ones. Biogenic chemicals are derived from biospheric carbon, which contains C. Carbon in artificially made chemicals is usually derived from fossil fuels like coal or petroleum , where

1919-475: Is MALDI-TOF , which refers to a combination of a matrix-assisted laser desorption/ionization source with a time-of-flight mass analyzer. Other examples include inductively coupled plasma-mass spectrometry (ICP-MS) , accelerator mass spectrometry (AMS) , thermal ionization-mass spectrometry (TIMS) and spark source mass spectrometry (SSMS) . Certain applications of mass spectrometry have developed monikers that although strictly speaking would seem to refer to

2020-440: Is ionized , for example by bombarding it with a beam of electrons . This may cause some of the sample's molecules to break up into positively charged fragments or simply become positively charged without fragmenting. These ions (fragments) are then separated according to their mass-to-charge ratio, for example by accelerating them and subjecting them to an electric or magnetic field: ions of the same mass-to-charge ratio will undergo

2121-423: Is " canal rays ". Wilhelm Wien found that strong electric or magnetic fields deflected the canal rays and, in 1899, constructed a device with perpendicular electric and magnetic fields that separated the positive rays according to their charge-to-mass ratio ( Q/m ). Wien found that the charge-to-mass ratio depended on the nature of the gas in the discharge tube. English scientist J. J. Thomson later improved on

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2222-443: Is a wide variety of ionization techniques, depending on the phase (solid, liquid, gas) of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample, which are then targeted through the mass analyzer and into the detector . The differences in masses of the fragments allows the mass analyzer to sort the ions by their mass-to-charge ratio. The detector measures

2323-424: Is also a very important tracer for describing the fate of nitrogenous organic pollutants . Nitrogen-15 tracing is an important method used in biogeochemistry . The ratio of stable nitrogen isotopes, N/ N or δ N , tends to increase with trophic level , such that herbivores have higher nitrogen isotope values than plants , and carnivores have higher nitrogen isotope values than herbivores. Depending on

2424-491: Is an example of the linear ion trap. A toroidal ion trap can be visualized as a linear quadrupole curved around and connected at the ends or as a cross-section of a 3D ion trap rotated on edge to form the toroid, donut-shaped trap. The trap can store large volumes of ions by distributing them throughout the ring-like trap structure. This toroidal shaped trap is a configuration that allows the increased miniaturization of an ion trap mass analyzer. Additionally, all ions are stored in

2525-446: Is applied to the endcap electrodes, and the trapping voltage amplitude and/or excitation voltage frequency is varied to bring ions into a resonance condition in order of their mass/charge ratio. The cylindrical ion trap mass spectrometer (CIT) is a derivative of the quadrupole ion trap where the electrodes are formed from flat rings rather than hyperbolic shaped electrodes. The architecture lends itself well to miniaturization because as

2626-501: Is applied. This filament emits electrons which ionize the compounds. The ions can then further fragment, yielding predictable patterns. Intact ions and fragments pass into the mass spectrometer's analyzer and are eventually detected. However, the high temperatures (300 °C) used in the GC-MS injection port (and oven) can result in thermal degradation of injected molecules, thus resulting in the measurement of degradation products instead of

2727-444: Is called isotope analysis . The atomic mass of different isotopes affect their chemical kinetic behavior, leading to natural isotope separation processes. For example, different sources and sinks of methane have different affinity for the C and C isotopes, which allows distinguishing between different sources by the C/ C ratio in methane in the air. In geochemistry , paleoclimatology and paleoceanography this ratio

2828-460: Is called δ C . The ratio is calculated with respect to Pee Dee Belemnite (PDB) standard : Similarly, carbon in inorganic carbonates shows little isotopic fractionation, while carbon in materials originated by photosynthesis is depleted of the heavier isotopes. In addition, there are two types of plants with different biochemical pathways; the C3 carbon fixation , where the isotope separation effect

2929-407: Is designed to pass the untrapped ions rather than collect the trapped ones, and is for that reason referred to as a transmission quadrupole. A magnetically enhanced quadrupole mass analyzer includes the addition of a magnetic field, either applied axially or transversely. This novel type of instrument leads to an additional performance enhancement in terms of resolution and/or sensitivity depending upon

3030-472: Is in protein identification. Tandem mass spectrometry enables a variety of experimental sequences. Many commercial mass spectrometers are designed to expedite the execution of such routine sequences as selected reaction monitoring (SRM), precursor ion scanning, product ion scanning, and neutral loss scanning. Another type of tandem mass spectrometry used for radiocarbon dating is accelerator mass spectrometry (AMS), which uses very high voltages, usually in

3131-472: Is more pronounced, C4 carbon fixation , where the heavier C is less depleted, and Crassulacean Acid Metabolism (CAM) plants, where the effect is similar but less pronounced than with C 4 plants. Isotopic fractionation in plants is caused by physical (slower diffusion of C in plant tissues due to increased atomic weight) and biochemical (preference of C by two enzymes: RuBisCO and phosphoenolpyruvate carboxylase ) factors. The different isotope ratios for

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3232-567: Is not conclusive evidence of life or of the microbial sulfate reduction pathway in the Archean. Hans Dehmelt Hans Georg Dehmelt ( German pronunciation: [ˈhans ˈɡeːɔʁk ˈdeːml̩t] ; 9 September 1922 – 7 March 2017) was a German and American physicist, who was awarded a Nobel Prize in Physics in 1989, for co-developing the ion trap technique ( Penning trap ) with Wolfgang Paul , for which they shared one-half of

3333-408: Is not suitable for coupling to HPLC , i.e. LC-MS , since at atmospheric pressure, the filaments used to generate electrons burn out rapidly. Thus EI is coupled predominantly with GC , i.e. GC-MS , where the entire system is under high vacuum. Hard ionization techniques are processes which impart high quantities of residual energy in the subject molecule invoking large degrees of fragmentation (i.e.

3434-451: Is possible to determine where a shipment of uranium oxide was produced. The rate of exchange of surface isotopes with the environment has to be taken in account. The oxygen isotopic signatures of solid samples (organic and inorganic) are usually measured with pyrolysis and mass spectrometry . Improper or prolonged storage of samples can lead to inaccurate measurements. Sulfur has four stable isotopes, S , S, S, and S, of which S

3535-417: Is similar to a mass spectrograph except that the beam of ions is directed onto a phosphor screen. A mass spectroscope configuration was used in early instruments when it was desired that the effects of adjustments be quickly observed. Once the instrument was properly adjusted, a photographic plate was inserted and exposed. The term mass spectroscope continued to be used even though the direct illumination of

3636-518: Is so rare that it is very difficult to detect (~0.04% abundant). The ratio of O / O in water depends on the amount of evaporation the water experienced (as O is heavier and therefore less likely to vaporize). As the vapor tension depends on the concentration of dissolved salts, the O/ O ratio shows correlation on the salinity and temperature of water. As oxygen is incorporated into the shells of calcium carbonate -secreting organisms, such sediments provide

3737-635: Is the most abundant by a large margin due to the fact it is created by the very common C in supernovas . Sulfur isotope ratios are almost always expressed as ratios relative to S due to this major relative abundance (95.0%). Sulfur isotope fractionations are usually measured in terms of δ S due to its higher abundance (4.25%) compared to the other stable isotopes of sulfur , though δ S is also sometimes measured. Differences in sulfur isotope ratios are thought to exist primarily due to kinetic fractionation during reactions and transformations. Sulfur isotopes are generally measured against standards; prior to 1993,

3838-485: Is the ratio of the m/z measurement error to the true m/z . Mass accuracy is usually measured in ppm or milli mass units . The mass range is the range of m/z amenable to analysis by a given analyzer. The linear dynamic range is the range over which ion signal is linear with analyte concentration. Speed refers to the time frame of the experiment and ultimately is used to determine the number of spectra per unit time that can be generated. A sector field mass analyzer uses

3939-636: Is used to dissociate stable gaseous molecules in a carrier gas of He or Ar. In instances where a synchrotron light source is utilized, a tuneable photon energy can be utilized to acquire a photoionization efficiency curve which can be used in conjunction with the charge ratio m/z to fingerprint molecular and ionic species. More recently atmospheric pressure photoionization (APPI) has been developed to ionize molecules mostly as effluents of LC-MS systems. Some applications for ambient ionization include environmental applications as well as clinical applications. In these techniques, ions form in an ion source outside

4040-606: The C originally present has decayed below detectable limits. The amount of C currently present in a sample therefore indicates the proportion of carbon of biogenic origin. Nitrogen-15 , or N, is often used in agricultural and medical research, for example in the Meselson–Stahl experiment to establish the nature of DNA replication . An extension of this research resulted in development of DNA-based stable-isotope probing, which allows examination of links between metabolic function and taxonomic identity of microorganisms in

4141-606: The Canyon Diablo troilite standard (abbreviated to CDT ), which has a S: S equal to 22.220, was used as both a reference material and the zero point for the isotopic scale. Since 1993, the Vienna-CDT standard has been used as a zero point, and there are several materials used as reference materials for sulfur isotope measurements . Sulfur fractionations by natural processes measured against these standards have been shown to exist between −72‰ and +147‰, as calculated by

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4242-666: The German Army , which ordered him to attend the University of Breslau to study physics in 1943. After a year of study he returned to army service and was captured during the Battle of the Bulge . After his release from an American prisoner of war camp in 1946, Dehmelt returned to his study of physics at the University of Göttingen , where he supported himself by repairing and bartering old, pre-war radio sets. He completed his master's thesis in 1948 and received his PhD in 1950, both from

4343-646: The isotopes of uranium during the Manhattan Project . Calutron mass spectrometers were used for uranium enrichment at the Oak Ridge, Tennessee Y-12 plant established during World War II. In 1989, half of the Nobel Prize in Physics was awarded to Hans Dehmelt and Wolfgang Paul for the development of the ion trap technique in the 1950s and 1960s. In 2002, the Nobel Prize in Chemistry

4444-443: The tissue being examined, there tends to be an increase of 3-4 parts per thousand with each increase in trophic level. The tissues and hair of vegans therefore contain significantly lower δ N than the bodies of people who eat mostly meat. Similarly, a terrestrial diet produces a different signature than a marine-based diet. Isotopic analysis of hair is an important source of information for archaeologists , providing clues about

4545-421: The (officially) dimensionless m/z , where z is the number of elementary charges ( e ) on the ion (z=Q/e). This quantity, although it is informally called the mass-to-charge ratio, more accurately speaking represents the ratio of the mass number and the charge number, z . There are many types of mass analyzers, using either static or dynamic fields, and magnetic or electric fields, but all operate according to

4646-417: The 1960s, Dehmelt and his students worked on spectroscopy of hydrogen and helium ions. The electron was finally isolated in 1973 with David Wineland, who continued work on trapped ions at NIST. He created the first geonium atom in 1976, which he then used to measure precise magnetic moments of the electron and positron with R. S. Van Dyck into the 1980s, work that led to his Nobel prize. In 1979 Dehmelt led

4747-535: The Earth's (within 4 ppm). In 2013, a study was released that indicated water in lunar magma was 'indistinguishable' from carbonaceous chondrites and nearly the same as Earth's, based on the composition of water isotopes. Isotope biogeochemistry has been used to investigate the timeline surrounding life and its earliest iterations on Earth . Isotopic fingerprints typical of life, preserved in sediments, have been used to suggest, but do not necessarily prove, that life

4848-513: The Solar System. For example, the Moon 's oxygen isotopic ratios seem to be essentially identical to Earth's. Oxygen isotopic ratios, which may be measured very precisely, yield a unique and distinct signature for each Solar System body. Different oxygen isotopic signatures can indicate the origin of material ejected into space. The Moon's titanium isotope ratio ( Ti/ Ti) appears close to

4949-675: The University of Göttingen. He was then invited to Duke University as a postdoctoral associate, emigrating in 1952. Dehmelt became an assistant professor at the University of Washington in Seattle, Washington in 1955, an associate professor in 1958, and a full professor in 1961. In 1955 he built his first electron impact tube in George Volkoff 's laboratory at the University of British Columbia and experimented on paramagnetic resonances in polarized atoms and free electrons. In

5050-475: The above differential equation. Each analyzer type has its strengths and weaknesses. Many mass spectrometers use two or more mass analyzers for tandem mass spectrometry (MS/MS) . In addition to the more common mass analyzers listed below, there are others designed for special situations. There are several important analyzer characteristics. The mass resolving power is the measure of the ability to distinguish two peaks of slightly different m/z . The mass accuracy

5151-406: The above expressions for the force applied to the ion yields: This differential equation is the classic equation of motion for charged particles . Together with the particle's initial conditions, it completely determines the particle's motion in space and time in terms of m/Q . Thus mass spectrometers could be thought of as "mass-to-charge spectrometers". When presenting data, it is common to use

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5252-436: The actual molecule(s) of interest. Isotopic signature An isotopic signature (also isotopic fingerprint ) is a ratio of non-radiogenic ' stable isotopes ', stable radiogenic isotopes , or unstable radioactive isotopes of particular elements in an investigated material. The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry against an isotopic reference material . This process

5353-412: The advent of stable isotope ratio mass spectrometry , isotopic signatures of materials find increasing use in forensics , distinguishing the origin of otherwise similar materials and tracking the materials to their common source. For example, the isotope signatures of plants can be to a degree influenced by the growth conditions, including moisture and nutrient availability. In case of synthetic materials,

5454-491: The analyte is ionized by chemical ion-molecule reactions during collisions in the source. Two techniques often used with liquid and solid biological samples include electrospray ionization (invented by John Fenn ) and matrix-assisted laser desorption/ionization (MALDI, initially developed as a similar technique "Soft Laser Desorption (SLD)" by K. Tanaka for which a Nobel Prize was awarded and as MALDI by M. Karas and F. Hillenkamp). In mass spectrometry, ionization refers to

5555-583: The ancient diets and differing cultural attitudes to food sources. A number of other environmental and physiological factors can influence the nitrogen isotopic composition at the base of the food web (i.e. in plants) or at the level of individual animals. For example, in arid regions, the nitrogen cycle tends to be more 'open' and prone to the loss of N, increasing δ N in soils and plants. This leads to relatively high δ N values in plants and animals in hot and arid ecosystems relative to cooler and moister ecosystems. Furthermore, elevated δ N have been linked to

5656-455: The atmosphere by industrial processes has an isotopic composition different from lead in minerals. Combustion of gasoline with tetraethyllead additive led to formation of ubiquitous micrometer-sized lead-rich particulates in car exhaust smoke ; especially in urban areas the man-made lead particles are much more common than natural ones. The differences in isotopic content in particles found in objects can be used for approximate geolocation of

5757-560: The atmosphere, and predict how changes in land use will affect climate change. Similarly, marine fish contain more C than freshwater fish, with values approximating the C 4 and C 3 plants respectively. The ratio of carbon-13 and carbon-12 isotopes in these types of plants is as follows: Limestones formed by precipitation in seas from the atmospheric carbon dioxide contain normal proportion of C. Conversely, calcite found in salt domes originates from carbon dioxide formed by oxidation of petroleum , which due to its plant origin

5858-414: The central location of the peaks, since the starting velocity of ions is generally centered at zero. To fix this problem, time-lag focusing/ delayed extraction has been coupled with TOF-MS. Quadrupole mass analyzers use oscillating electrical fields to selectively stabilize or destabilize the paths of ions passing through a radio frequency (RF) quadrupole field created between four parallel rods. Only

5959-516: The detector consists of a pair of metal surfaces within the mass analyzer/ion trap region which the ions only pass near as they oscillate. No direct current is produced, only a weak AC image current is produced in a circuit between the electrodes. Other inductive detectors have also been used. A tandem mass spectrometer is one capable of multiple rounds of mass spectrometry, usually separated by some form of molecule fragmentation. For example, one mass analyzer can isolate one peptide from many entering

6060-438: The detector first. Ions usually are moving prior to being accelerated by the electric field , this causes particles with the same m/z to arrive at different times at the detector. This difference in initial velocities is often not dependent on the mass of the ion, and will turn into a difference in the final velocity. This distribution in velocities broadens the peaks shown on the count vs m/z plot, but will generally not change

6161-424: The detector is located. Ions of different mass are resolved according to impact time. The final element of the mass spectrometer is the detector. The detector records either the charge induced or the current produced when an ion passes by or hits a surface. In a scanning instrument, the signal produced in the detector during the course of the scan versus where the instrument is in the scan (at what m/Q ) will produce

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6262-409: The environment, without the need for culture isolation. Proteins can be isotopically labelled by cultivating them in a medium containing N as the only source of nitrogen, e.g., in quantitative proteomics such as SILAC . Nitrogen-15 is extensively used to trace mineral nitrogen compounds (particularly fertilizers ) in the environment. When combined with the use of other isotopic labels, N

6363-566: The following equation: δ S 34 s a m p l e = ( S 34 / 32 S sample S 34 / 32 S s t a n d a r d − 1 ) ⋅ 1000 {\displaystyle \delta {\ce {^{34}S}}_{\mathrm {sample} }=\left({\frac {{\ce {^{34}S/^{32}S}}_{{\ce {sample}}}}{{\ce {^{34}S/^{32}S}}_{\mathrm {standard} }}}-1\right)\cdot 1000} As

6464-430: The geologic record before about 2.45 billion years ago, and these isotopic signatures have since ceded to mass-dependent fractionation, providing strong evidence that the atmosphere shifted from anoxic to oxygenated at that threshold. Modern sulfate-reducing bacteria are known to favorably reduce lighter S instead of S, and the presence of these microorganisms can measurably alter the sulfur isotope composition of

6565-457: The identification of known molecules it is also useful for identifying unknowns using its similarity searching/analysis. All tandem mass spectrometry data comes from the experimental analysis of standards at multiple collision energies and in both positive and negative ionization modes. When a specific combination of source, analyzer, and detector becomes conventional in practice, a compound acronym may arise to designate it succinctly. One example

6666-492: The inferred seawater composition may be evidence of life. This claim is not clear-cut, however, and is sometimes contested using geologic evidence from the ~3.49 Ga sulfide minerals found in the Dresser Formation of Western Australia, which are found to have δ S values as negative as −22‰. Because it has not been proven that the sulfide and barite minerals formed in the absence of major hydrothermal input, it

6767-403: The ions according to their mass-to-charge ratio . The following two laws govern the dynamics of charged particles in electric and magnetic fields in vacuum: Here F is the force applied to the ion, m is the mass of the ion, a is the acceleration, Q is the ion charge, E is the electric field, and v × B is the vector cross product of the ion velocity and the magnetic field Equating

6868-416: The ions are injected into a Penning trap (a static electric/magnetic ion trap ) where they effectively form part of a circuit. Detectors at fixed positions in space measure the electrical signal of ions which pass near them over time, producing a periodic signal. Since the frequency of an ion's cycling is determined by its mass-to-charge ratio, this can be deconvoluted by performing a Fourier transform on

6969-562: The ions are trapped and sequentially ejected. Ions are trapped in a mainly quadrupole RF field, in a space defined by a ring electrode (usually connected to the main RF potential) between two endcap electrodes (typically connected to DC or auxiliary AC potentials). The sample is ionized either internally (e.g. with an electron or laser beam), or externally, in which case the ions are often introduced through an aperture in an endcap electrode. There are many mass/charge separation and isolation methods but

7070-417: The ions in a certain range of mass/charge ratio are passed through the system at any time, but changes to the potentials on the rods allow a wide range of m/z values to be swept rapidly, either continuously or in a succession of discrete hops. A quadrupole mass analyzer acts as a mass-selective filter and is closely related to the quadrupole ion trap , particularly the linear quadrupole ion trap except that it

7171-500: The isotopic composition of its constituents (the ratio of Cl to Cl). The ion source is the part of the mass spectrometer that ionizes the material under analysis (the analyte). The ions are then transported by magnetic or electric fields to the mass analyzer. Techniques for ionization have been key to determining what types of samples can be analyzed by mass spectrometry. Electron ionization and chemical ionization are used for gases and vapors . In chemical ionization sources,

7272-655: The isotopic composition of uranium to ensure none is diverted for nefarious purposes. It would thus become apparent quickly if another Uranium deposit besides Oklo proves to have once been a natural nuclear fission reactor. In archaeological studies, stable isotope ratios have been used to track diet within the time span formation of analyzed tissues (10–15 years for bone collagen and intra-annual periods for tooth enamel bioapatite) from individuals; "recipes" of foodstuffs (ceramic vessel residues); locations of cultivation and types of plants grown (chemical extractions from sediments); and migration of individuals (dental material). With

7373-423: The isotopic ratio of proteins; in an unadulterated honey the carbon isotopic ratios of sugars and proteins should match. As low as 7% level of addition can be detected. Nuclear explosions form Be by a reaction of fast neutrons with C in the carbon dioxide in air. This is one of the historical indicators of past activity at nuclear test sites. Isotopic fingerprints are used to study the origin of materials in

7474-492: The leaf level, but also during wood formation. Many recent studies combine leaf level isotopic fractionation with annual patterns of wood formation (i.e. tree ring δ C) to quantify the impacts of climatic variations and atmospheric composition on physiological processes of individual trees and forest stands. The next phase of understanding, in terrestrial ecosystems at least, seems to be the combination of multiple isotopic proxies to decipher interactions between plants, soils and

7575-408: The magnetic force to a greater degree than heavier ions (based on Newton's second law of motion , F = ma ). The streams of magnetically sorted ions pass from the analyzer to the detector, which records the relative abundance of each ion type. This information is used to determine the chemical element composition of the original sample (i.e. that both sodium and chlorine are present in the sample) and

7676-413: The magnitude and orientation of the applied magnetic field. A common variation of the transmission quadrupole is the triple quadrupole mass spectrometer. The "triple quad" has three consecutive quadrupole stages, the first acting as a mass filter to transmit a particular incoming ion to the second quadrupole, a collision chamber, wherein that ion can be broken into fragments. The third quadrupole also acts as

7777-430: The mass resolving and mass determining capabilities of mass spectrometry is using it in tandem with chromatographic and other separation techniques. A common combination is gas chromatography-mass spectrometry (GC/MS or GC-MS). In this technique, a gas chromatograph is used to separate different compounds. This stream of separated compounds is fed online into the ion source, a metallic filament to which voltage

7878-849: The mass spectrometer. Sampling becomes easy as the samples don't need previous separation nor preparation. Some examples of ambient ionization techniques are Direct Analysis in Real Time (DART), DESI , SESI , LAESI , desorption atmospheric-pressure chemical ionization (DAPCI), Soft Ionization by Chemical Reaction in Transfer (SICRT) and desorption atmospheric pressure photoionization DAPPI among others. Others include glow discharge , field desorption (FD), fast atom bombardment (FAB), thermospray , desorption/ionization on silicon (DIOS), atmospheric pressure chemical ionization (APCI), secondary ion mass spectrometry (SIMS), spark ionization and thermal ionization (TIMS). Mass analyzers separate

7979-460: The mega-volt range, to accelerate negative ions into a type of tandem mass spectrometer. The METLIN Metabolite and Chemical Entity Database is the largest repository of experimental tandem mass spectrometry data acquired from standards. The tandem mass spectrometry data on over 930,000 molecular standards (as of January 2024) is provided to facilitate the identification of chemical entities from tandem mass spectrometry experiments. In addition to

8080-407: The most commonly used is the mass instability mode in which the RF potential is ramped so that the orbit of ions with a mass a > b are stable while ions with mass b become unstable and are ejected on the z -axis onto a detector. There are also non-destructive analysis methods. Ions may also be ejected by the resonance excitation method, whereby a supplemental oscillatory excitation voltage

8181-733: The object's origin. Hot particles , radioactive particles of nuclear fallout and radioactive waste , also exhibit distinct isotopic signatures. Their radionuclide composition (and thus their age and origin) can be determined by mass spectrometry or by gamma spectrometry . For example, particles generated by a nuclear blast contain detectable amounts of Co and Eu . The Chernobyl accident did not release these particles but did release Sb and Ce . Particles from underwater bursts will consist mostly of irradiated sea salts. Ratios of Eu / Eu, Eu/ Eu, and Pu / Pu are also different for fusion and fission nuclear weapons , which allows identification of hot particles of unknown origin. Uranium has

8282-448: The ocean. Because the δ S values of sulfide minerals is primarily influenced by the presence of sulfate-reducing bacteria , the absence of sulfur isotope fractionations in sulfide minerals suggests the absence of these bacterial processes or the absence of freely available sulfate. Some have used this knowledge of microbial sulfur fractionation to suggest that minerals (namely pyrite ) with large sulfur isotope fractionations relative to

8383-402: The origin of a common brown PSA packaging tape by using the carbon, oxygen, and hydrogen isotopic signature of the backing polymer, additives, and adhesive . Measurement of carbon isotopic ratios can be used for detection of adulteration of honey . Addition of sugars originated from corn or sugar cane (C4 plants) skews the isotopic ratio of sugars present in honey, but does not influence

8484-408: The preferential excretion of 14N and reutilization of already enriched 15N tissues in the body under prolonged water stress conditions or insufficient protein intake. δ N also provides a diagnostic tool in planetary science as the ratio exhibited in atmospheres and surface materials "is closely tied to the conditions under which materials form". Oxygen occurs naturally in three variants, but O

8585-578: The prize (the other half of the Prize in that year was awarded to Norman Foster Ramsey ). Their technique was used for high precision measurement of the electron magnetic moment . At the age of ten Dehmelt enrolled in the Berlinisches Gymnasium zum Grauen Kloster , a Latin school in Berlin , where he was admitted on a scholarship. After graduating in 1940, he volunteered for service in

8686-617: The production of gas phase ions suitable for resolution in the mass analyser or mass filter. Ionization occurs in the ion source . There are several ion sources available; each has advantages and disadvantages for particular applications. For example, electron ionization (EI) gives a high degree of fragmentation, yielding highly detailed mass spectra which when skilfully analysed can provide important information for structural elucidation/characterisation and facilitate identification of unknown compounds by comparison to mass spectral libraries obtained under identical operating conditions. However, EI

8787-434: The recorded image currents. Orbitraps have a high mass accuracy, high sensitivity and a good dynamic range. Fourier-transform mass spectrometry (FTMS), or more precisely Fourier-transform ion cyclotron resonance MS, measures mass by detecting the image current produced by ions cyclotroning in the presence of a magnetic field. Instead of measuring the deflection of ions with a detector such as an electron multiplier ,

8888-405: The same amount of deflection. The ions are detected by a mechanism capable of detecting charged particles, such as an electron multiplier . Results are displayed as spectra of the signal intensity of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses (e.g. an entire molecule) to the identified masses or through

8989-631: The same trapping field and ejected together simplifying detection that can be complicated with array configurations due to variations in detector alignment and machining of the arrays. As with the toroidal trap, linear traps and 3D quadrupole ion traps are the most commonly miniaturized mass analyzers due to their high sensitivity, tolerance for mTorr pressure, and capabilities for single analyzer tandem mass spectrometry (e.g. product ion scans). Orbitrap instruments are similar to Fourier-transform ion cyclotron resonance mass spectrometers (see text below). Ions are electrostatically trapped in an orbit around

9090-421: The sample is vaporized (turned into gas ) and ionized (transformed into electrically charged particles) into sodium (Na) and chloride (Cl) ions. Sodium atoms and ions are monoisotopic , with a mass of about 23 daltons (symbol: Da or older symbol: u). Chloride atoms and ions come in two stable isotopes with masses of approximately 35 u (at a natural abundance of about 75 percent) and approximately 37 u (at

9191-402: The second ionization energy of all except the most electropositive metals. The heating is achieved by a radio-frequency current passed through a coil surrounding the plasma. Photoionization can be used in experiments which seek to use mass spectrometry as a means of resolving chemical kinetics mechanisms and isomeric product branching. In such instances a high energy photon, either X-ray or uv,

9292-408: The signal. FTMS has the advantage of high sensitivity (since each ion is "counted" more than once) and much higher resolution and thus precision. Ion cyclotron resonance (ICR) is an older mass analysis technique similar to FTMS except that ions are detected with a traditional detector. Ions trapped in a Penning trap are excited by an RF electric field until they impact the wall of the trap, where

9393-417: The signature is influenced by the conditions during the chemical reaction. The isotopic signature profiling is useful in cases where other kinds of profiling, e.g. characterization of impurities , are not optimal. Electronics coupled with scintillator detectors are routinely used to evaluate isotope signatures and identify unknown sources. A study was published demonstrating the possibility of determination of

9494-436: The size of a trap is reduced, the shape of the electric field near the center of the trap, the region where the ions are trapped, forms a shape similar to that of a hyperbolic trap. A linear quadrupole ion trap is similar to a quadrupole ion trap, but it traps ions in a two dimensional quadrupole field, instead of a three-dimensional quadrupole field as in a 3D quadrupole ion trap. Thermo Fisher's LTQ ("linear trap quadrupole")

9595-462: The subject molecule and as such result in little fragmentation. Examples include fast atom bombardment (FAB), chemical ionization (CI), atmospheric-pressure chemical ionization (APCI), atmospheric-pressure photoionization (APPI), electrospray ionization (ESI), desorption electrospray ionization (DESI), and matrix-assisted laser desorption/ionization (MALDI). Inductively coupled plasma (ICP) sources are used primarily for cation analysis of

9696-405: The systematic rupturing of bonds acts to remove the excess energy, restoring stability to the resulting ion). Resultant ions tend to have m/z lower than the molecular ion (other than in the case of proton transfer and not including isotope peaks). The most common example of hard ionization is electron ionization (EI). Soft ionization refers to the processes which impart little residual energy onto

9797-693: The two kinds of plants propagate through the food chain , thus it is possible to determine if the principal diet of a human or an animal consists primarily of C 3 plants ( rice , wheat , soybeans , potatoes ) or C 4 plants ( corn , or corn-fed beef ) by isotope analysis of their flesh and bone collagen (however, to obtain more accurate determinations, carbon isotopic fractionation must be also taken into account, since several studies have reported significant C discrimination during biodegradation of simple and complex substrates). Within C3 plants processes regulating changes in δ C are well understood, particularly at

9898-401: The value of an indicator quantity and thus provides data for calculating the abundances of each ion present. Some detectors also give spatial information, e.g., a multichannel plate. The following describes the operation of a spectrometer mass analyzer, which is of the sector type. (Other analyzer types are treated below.) Consider a sample of sodium chloride (table salt). In the ion source,

9999-402: The work of Wien by reducing the pressure to create the mass spectrograph. The word spectrograph had become part of the international scientific vocabulary by 1884. Early spectrometry devices that measured the mass-to-charge ratio of ions were called mass spectrographs which consisted of instruments that recorded a spectrum of mass values on a photographic plate . A mass spectroscope

10100-526: Was already in existence on Earth by 3.85 billion years ago. Sulfur isotope evidence has also been used to corroborate the timing of the Great Oxidation Event , during which the Earth's atmosphere experienced a measurable rise in oxygen (to about 9% of modern values ) for the first time about 2.3–2.4 billion years ago. Mass-independent sulfur isotope fractionations are found to be widespread in

10201-424: Was awarded to John Bennett Fenn for the development of electrospray ionization (ESI) and Koichi Tanaka for the development of soft laser desorption (SLD) and their application to the ionization of biological macromolecules , especially proteins . A mass spectrometer consists of three components: an ion source, a mass analyzer, and a detector. The ionizer converts a portion of the sample into ions. There

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