Quadrupole mass spectrometers

Quadrupole mass spectrometers (mass filters) allow ions at each m/z value to pass through sequentially for example, ions at m/z 100, 101, 102 will pass one after the other through the quadrupole assembly so that first m/z 100 is transmitted, then m/z 101, then m/z 102 (or vice versa), and so on. Therefore, the ion collector (or detector) at the end of the quadrupole unit needs to cover only one point or focus in space (Figure 29.1a), and a complete mass spectrum is recorded over a period of time. The ions arrive at the collector sequentially, and ions are detected in a time domain, not in a spatial domain.  [c.205]

Metastable ions formed in any of these field-free regions can be detected by specialized changes in the various electric and/or magnetic fields (linked scanning) without interference from normal ions formed in the source. In a one-sector magnetic instrument there are only two field-free regions. In tandem MS (mass spectrometry), there is always one more possible field-free region than there are sectors for example, a four-sector instrument has five such regions although, in practice, only one or two are used for metastable ion observations. In a simple quadrupole mass spectrometer, differentiation between normal and metastable ions is not possible but can be carried out efficiently  [c.226]

For a quadrupole mass spectrometer, this high rate of scanning is not difficult because it requires only simple changes in some electrical voltages, and these changes can be made electronically at very high speed, which is why quadrupoles are popular in GC/MS combinations. In the early days of magnetic-sector mass spectrometers, the required scanning speed was not possible because of serious hysteresis effects in the magnets. With modem magnet technology, scanning can be done  [c.255]

For a quadrupole mass spectrometer, this high rate of scanning is not difficult because it requires only simple changes in some electrical voltages, and these changes can be made electronically at very high speed, which is one reason why quadmpoles are popular in LC/MS combinations. In the early days of magnetic-sector mass spectrometers, the required scanning speed was not possible because of serious hysteresis effects in the magnets. With modem magnet technology, scanning can be done at high speed with insignificant hysteresis, and magnetic-sector instruments can now compete with quadmpoles. While ultimate. scan speed for a magnetic instrument is not as good as the quadrupole s, the former does have the advantage of providing greater mass resolution at higher mass.  [c.264]

Normal ions are readily and easily observed by quadrupole mass spectrometers.  [c.412]

Table 2. Scan Functions for a Triple Quadrupole Mass Spectrometer Table 2. Scan Functions for a Triple Quadrupole Mass Spectrometer
Instrument configurations other than a magnetic-sector mass spectrometer with a pin sample source are also suitable for analytical GDMS, but with some compromise in analytical performance. If analysis to ultratrace levels is not required, but only measurements to levels well above the background of isobaric mass spectral interferences, low-resolution quadrupole mass spectrometer based instruments can be configured. Such instruments have recendy been made available by several instrument manufacturers. In these cases, the unique advant e of GDMS lies not with the ultratrace capability but with the fiiU elemental coverage from matrix concentrations to levels of 0.01-0.1 ppm. Also, quadrupole MS mass spectral analysis requires significandy less time, enabling the more rapid analysis suitable for depth profiling of films.  [c.612]

The mass spectrometer usually found on ICPMS instruments is a quadrupole mass spectrometer. This gives high throughput of ions and resolutions of 1 amu. Only a  [c.625]

A quadrupole mass spectrometer allows ions of a specific charge-to-mass ratio to pass through on a trajectory to reach the detector. This is accomplished by applying dc and rf potentials to four rods (hence the name quadrupole) that can be tuned to achieve different mass conductances through the spectrometer. The detector only counts ions, it is the quadrupole tuning that determines which ions are counted. The quadrupole can be tuned through a wide mass range quickly a scan from 1 amu to 240 amu can take less than a second. An increased signal-to-noise ratio is accomplished by time averaging many scans.  [c.626]

Quadrupole Mass Spectrometers  [c.89]

TDS, sometimes called temperature-programmed desorption (TPD), is simple in principle. A gas or mixture of gases is adsorbed on a clean metal foil for a chosen time then, after the gas is pumped away, the foil is heated, at a strictly linear rate, to a high temperature, during which the current of a particular ion or group of ions is monitored as a function of temperature. The ion masses are selected in a quadrupole mass spectrometer. As the binding energy thresholds of the adsorbed species on the surface are crossed, peaks in the desorbed ion current appear at characteristic temperatures. From the characteristic temperatures and the shape of the desorption peak above the threshold, the activation energies for desorption can be obtained, along with information about the nature of the desorption process. The mass spectrum from the mass spectrometer, of course, provides information about the species that actually occur on the surface after adsorption.  [c.178]

These authors also analysed marine diesel fuel with GC X GC, connected to a quadrupole mass spectrometer for identification purposes, although the scan speed of the spectrometer was not quite suited for the fast second-dimension peaks  [c.400]

Brodbelt J, Liou C-C and Donovan T 1991 Selective adduct formation by dimethyl ether chemical ionization is a quadrupole ion trap mass spectrometer and a conventional ion source Ana/. Chem. 63 1205-9  [c.1359]

DSI is discussed in Part C (Chapter 17), since the approach usually requires an initial evaporation of solvent from a solution by moderate heating in a gas stream so as to leave the solute (the analytical sample). The resulting residual sample is then heated strongly to vaporize it. Typically, a solution is placed onto a heat-resistant wire or onto a graphite probe, and then the solvent is allowed to evaporate or is encouraged to do so by application of heat, directly or indirectly. The residual solid on its metal or graphite support is placed just below the plasma flame, which is allowed to stabilize for a short time. The probe and sample are then driven into the high-temperature flame, which causes vaporization, fragmentation, and ionization (Figure 16.2). Because the heat capacity of the flame is relatively small, the sample holder and sample should have as low a thermal mass as possible so as not to interfere with the operation of the flame. With the direct-insertion method, samples appear transiently in the flame therefore, if a wide range of elements is to be examined, the mass spectrometer should be one that can span a wide m/z range in the short space of time the sample takes to pass through the flame (quadrupole, time-of-flight). Further details of the DSI technique are discussed in Part C (Chapter 17).  [c.105]

Charged species such as ions, when passing through magnetic or electric fields (sectors), experience a force that deflects them from their original trajectory. This effect is utilized in magnetic-sector mass spectrometers to separate ions according to mass or, strictly, mass-to-charge ratio (m/z), the deflection being related to m/z and magnetic field strength (see Chapter 24). In a quadrupole instmment, only electric fields are used to separate ions according to mass. The ions are separated as they pass along the central axis of four parallel, equidistant rods (poles) that have DC and alternating (radio frequency, RF) voltages applied to them (Figure 25.1).  [c.183]

Thus, where magnetic sector and quadrupole instruments might be considered for a particular application, ultimate resolving power could be a decisive factor. For example, for use in a gas chromatograph/mass spectrometer combination (GC/MS), because most compounds that are volatile enough to pass through the GC will have relative molecular masses of well under 800, the lower ultimate resolving power of the quadrupole is less important, and its lower cost becomes decidedly advantageous.  [c.185]

Some Factors Important in Choosing between Quadrupole and Magnetic-Sector Mass Spectrometers  [c.186]

Modem mass spectrometers are used in a very wide variety of situations, so it is almost impossible to have a simple set of criteria that would determine whether a quadrupole or magnetic sector instmment would be best for any particular application. Nevertheless, some attempt is made here to address major considerations, mostly relating to cost.  [c.186]

All mass spectrometers analyze ions for their mass-to-charge ratios (m/z values) by separating the individual m/z values and then recording the numbers (abundance) of ions at each m/z value to give a mass spectrum. Quadrupoles allow ions of different m/z values to pass sequentially e.g., ions at m/z 100, 101, 102 will pass one after the other through the quadrupole assembly so that first m/z 100 is passed, then 101, then 102 (or vice versa), and so on. Therefore, the ion collector (or detector) at the end of the quadrupole assembly needs only to cover one point or focus for a whole spectrum to be scanned over a period of time (Figure 28.1a). This type of point detector records ion arrivals in a time domain, not a spatial one.  [c.201]

A magnetic-sector instrument separates ions according to their m/z values, but, unlike the quadrupole, it can also separate the ions by dispersing them in space (Figure 29.1b). The arrival of the dispersed ions can be recorded simultaneously in space (array or photographic plate focal-plane detection. Figure 29.1b), or, by manipulating the strength of the magnetic field, the ions can be brought sequentially to a focus at a point ion collector (Figure 29.1c). Other types of mass spectrometer can use point, array, or both types of ion detection. A time-of-flight (TOF) mass spectrometer collects ions sequentially and uses an array that is also a sequential detector (time-to-digital converter, TDC).  [c.205]

Besides obtaining this information from the electric/magnetic-sector methods described previously, this same information on ion connections can also be obtained quickly from collision-induced fragmentations in triple quadrupoles (see Chapter 33), in hybrid instruments having two mass analyzers — as in the Q/TOF (quadrupole and time-of-flight) instruments (see Chapter 23) — or in instruments having two successive magnetic sectors. These sorts of mass spectrometer are frequently used with ionization methods that give stable molecular ions with no tendency to fragment. If structural information is to be obtained in such cases, it is necessary to activate the molecular ions, which is usually done by colliding them with neutral gas molecules in a special  [c.243]

Peak matching can be done on quadrupole and magnetic-sector mass spectrometers, but only the latter, particularly as double-focusing instruments, have sufficiently high resolution for the technique to be useful at high mass.  [c.274]

The ease of vaporization of a sample can be an overriding factor in choice of mass spectrometer. Generally, the three phases — gas, liquid, and solid — need to be considered. By definition, a gas is volatile, and inserting a gas into a mass spectrometer is easy. A simple system of valves and filters is sufficient for transferring a gas into the vacuum of a mass spectrometer, and often an El source is all that is needed. Additionally, gases tend to be of low molecular mass, so ion analyzers for gases need not be very sophisticated or have more than a modest resolving power to cover the range needed (often less than an upper limit of m/z 100-150). Mass spectrometers for such purposes can be very small and light, and they are used on space probes to other planets. Similarly, small mass spectrometers (usually quadrupole instruments) are used to monitor atmospheres on earth in places where noxious substances may be present. These small mass spectrometers can be used in and transported by small vans or cars.  [c.278]

The ability of an analyzer to effect unit resolution of m/z values is important. It is useful to differentiate a working resolution from a best resolution. For obvious reasons, a mass spectrometer manufacturer will want to quote the best measured resolution attainable on any one instrument, but the purchaser needs to remember that this measurement will have been obtained when everything is working perfectly. Under everyday conditions, the mass spectrometer is unlikely to be operating even close to this best limit therefore effective resolving power is likely to be much lower than the best as stated in a brochure. As a rough guide, it is probably reasonable to subtract 10-15% from best-resolution figures to get some idea of the effective resolution obtainable under normal working conditions. Even then, choice of analyzer is not necessarily easy. As a general guide, up to m/z 600-1000 with unit mass resolution, all types of analyzer will be sufficient, but the quadrupole or ion trap is likely to be cheapest. As the working range increases, the quadrupoles and ion traps begin to drop out of consideration, and TOF or sector instruments come to the fore. Of these, the TOF is good up to m/z 3000-5000, although the higher mass ranges would probably need to include the use of a reflectron. As with the quadrupoles and ion traps, the TOF instruments are robust and easy to operate. Ion cyclotron resonance instruments may also be used at high m/z values if operated in Fourier-transform mode.  [c.281]

A major divergence appears for ion traps and ion cyclotron resonance (ICR) mass spectrometers, In both of these, MS/MS can be carried out without the need for a second analyzer. The differentiation is made possible by the length of time ion traps or ICR instruments can hold selected ions in their mass analyzers. For quadrupoles, magnetic sectors, and TOF analyzers, the ions generated in an ion source pass once through the analyzer, usually within a few microseconds. For ion traps and ICR instruments, ions can be retained in the trap or resonance cell for periods of milliseconds. In the latter case, it becomes possible to select ions at low background gas pressure, to collisionally activate these ions by increasing their velocity relative to background bath gas for a short time, and then to examine the resulting fragment ions. It is even possible to carry out MS" analyses, where n can be from two to about five. Ion traps, like quadrupoles, are limited in ultimate mass that can be measured, but they provide a relatively cheap introduction to MS/MS, The ICR instruments tend to be as expensive as bigger hybrid instruments, but they can also be used in MS measurements.  [c.282]

Electrospray can be used with sector, time-of-flight, and quadrupole instruments. The technique has been used extensively to couple liquid chromatographs to mass spectrometers.  [c.390]

The choice of mass spectrometer for a particular analysis depends on the namre of the sample and the desired results. For low detection limits, high mass resolution, or stigmatic imaging, a magnetic sector-based instrument should be used. The analysis of dielectric materials (in many cases) or a need for ultrahigh depth resolution requires the use of a quadrupole instrument.  [c.548]

It is very evident in Figure 3 that the chemical complexity of Hasteloy presents special problems for mass spectrometric analysis using a quadrupole mass spectrometer with low mass resolution. Molecular ions comprised of combinations of matrix and plasma atoms are formed in abundance and will obscure many elements  [c.577]

Molecular ion mass interferences are not as prevalent for the simpler matrices, as is clear from the mass spectrum obtained for the Pechiney 11630 A1 standard sample by electron-gas SNMSd (Figure 4). For metals like high-purity Al, the use of the quadrupole mass spectrometer can be quite satisfiictory. The dopant elements are present in this standard at the level of several tens of ppm and are quite evident in the mass spectrum. While the detection limit on the order of one ppm is comparable to that obtained from optical techniques, the elemental coverage by SNMS is much more comprehensive.  [c.578]

Demonstration of GDMS feasibility and research into glow-discharge processes has been carried out almost exclusively using the combination of a glow-discharge ion source with a quadrupole mass spectrometer (GDQMS). The combination is inexpensive, readily available and suitable for such purposes. In addition, the quadru-  [c.611]

The sensitivity factors summarized in Figure 2 are appropriate for analyses using a particular instrument (the VG 9000 GDMS) under specific glow-discharge conditions (3 mA and 1000 V in Ar, with cryocooling of the ion source) and with a well-controlled sample configuration in the source. RSFs depend on the sample-source configuration. In particular, they vary significantly with the spacing between the sample and the ion exit aperture from the cell. Use of the factors shown in Figure 2 under closely similar conditions will result in measurements with 20% accuracy. These factors can also be used to reduce the data obtained on other instruments, but the accuracy of the results will be reduced. In particular, the factors shown can be only approximately valid for results obtained using a quadrupole mass spectrometer, since ion-transmission characteristics differ significandy between the quadrupole mass spectrometer and the magnetic-sector spectrometer used to obtain the results of Figure 2.  [c.615]

Quadrupole mass spectrometers have been in use for many years as residual gas analyzers (with an ionizing hot filament) and in desorption studies and SSIMS. They consist of four circular rods, or poles, arranged equally spaced in a rectangular array and exactly coaxial. Figure 3.3 indicates the arrangement, as depicted by Krauss and Gruen [3.8]. Two voltages are applied to the rods, a dc voltage (Udc) and an rf voltage (Urf L/qCOS art). When an ion with a certain mass-to-charge ratio, m/q enters the space between the rods it is accelerated by the electrostatic field and for a particular combination of dc and rf voltages the ion has a stable trajectory and passes to a detector. For other combinations of voltages, the trajectory diverges rapidly and the ion is lost either as a result of hitting one of the poles or by passing between them to another part of the system. The mass resolution is governed by the dimensions of the mass spectrometer, the accuracy of its construction, and the stability and reproducibility of the ramped voltage. The quadrupole mass spectrometer is compact, does not require magnets, and is entirely ultra-high vacuum compatible - hence its popularity. It does have disadvantages, however, in that its transmission (typically <1%) is very low and decreases with increasing mass number. It is, furthermore, a scanning instrument enabling only sequential transmission of ions, all other ions being discarded. The information loss is, therefore, very high.  [c.89]

For IBSCA analysis, standard HV or, better, UHV-equipment with turbomolecular pump and a residual gas pressure of less than 10 Pa is necessary. As is apparent from Fig. 4.46, the optical detection system, which consists of transfer optics, a spectrometer, and a lateral-sensitive detector, is often combined with a quadrupole mass spectrometer for analysis of secondary sputtered particles (ions or post-ionized neutrals).  [c.242]

G. J. Opiteck, J. W. Jorgenson, M. A. Moseley III and R. J. Anderegg, Two-dimensional mia ocolumn HPLC coupled to a single-quadrupole mass spectrometer for the elucidation of sequence tags and peptide mapping , 7. Microcolumn Sep. 10 365-375 (1998).  [c.291]

A solution containing the analyte of interest is sprayed from the end of a capillary by application of a high electric potential. The resulting charged droplets are stripped of solvent, and ions formed from analyte molecules are directed electrically into the mass spectrometer (Z-spray). The ion beam passes into a quadrupole analyzer, which can be operated in a narrow band-pass mode so as to transmit ions of defined m/z values or in its wide band-pass mode, in which all ions are transmitted regardless of m/z value. There is a further focusing hexapole, after which the ion beam is focused and accelerated by an electric lens before being passed into the TOF analyzer in front of a deflector electrode. A high electric potential is applied to this electrode in pulses so that, at each pulse, a section of the ion beam is deflected and accelerated into the TOF analyzer. After reflection by the reflectron, the ions are detected at a microchannel plate multipoint collector. The reflectron is used mainly to increase the time intervals at which successive m/z values are detected at the collector and to improve focusing. The quadrupole is operated in the narrow band-pass mode for MS/MS and in its wide band-pass mode for obtaining a full spectrum by the TOF analyzer.  [c.155]

The term Q/TOF is used to describe a type of hybrid mass spectrometer system in which a quadrupole analyzer (Q) is used in conjunction with a time-of-flight analyzer (TOP). The use of two analyzers together (hybridized) provides distinct advantages that cannot be achieved by either analyzer individually. In the Q/TOF, the quadrupole is used in one of two modes to select the ions to be examined, and the TOF analyzer measures the actual mass spectrum. Hexapole assemblies are also used to help collimate the ion beams. The hybrid orthogonal Q/TOF instrument is illustrated in Figure 23.1.  [c.169]

The fundamentals of the ion optics for magnetic and electric sector, quadrupole, ion trap, and Fourier-transform ion cyclotron resonance (FTICR) mass spectrometers range from fairly simple to difficult. The basic ion optics of time-of-flight (TOF) instruments are very straightforward. Basically, ions need to be extracted from an ion source in short pulses and then directed down an evacuated straight tube to a detector. The time taken to travel the length of the drift or flight tube depends on the mass of the ion and its charge. For singly charged ions (z = 1 m/z = m), the time taken to traverse the distance from the source to the detector is proportional to a function of mass The greater the mass of the ion, the slower it is in arriving at the detector. Thus, there are no electric or magnetic fields to constrain the ions into curved or complicated trajectories. After initial acceleration, the ions pass in a straight line, at constant speed, to the detector. The arrival of the ions at the detector is recorded in the usual way as a trace of ion abundance against time of arrival, the latter being converted into a mass scale to give the final mass spectrum.  [c.189]

Ions produced in an ion source can be separated into their m/z values by a variety of analyzers. The resultant set of m/z values, along with the numbers (abundances) of ions, forms the mass spectrum. The separation of ions into their individual m/z values has been effected by analyzers utilizing magnetic fields or RF (radio frequency) electric fields. For example, the mass analysis of ions by instruments using a magnetic field is well known, as are instruments having quadru-pole RF electric fields (quadrupole, ion trap). Ions can also be dispersed in time, so their m/z values are measured according to their flight times in a time-of-flight (TOF) instrument. These individual pieces of equipment have their own characteristics and are commonly used in mass spectrometry. In addition, combinations of sectors have given rise to hybrid instruments. The earliest of these was the double-focusing mass spectrometer having an electric. sector to focus ions according to their energies and then a magnetic sector to separate the individual m/z values. There is now a whole series of hybrid types, each with some advantage over nonhybrids. Ion collectors have seen a similar improvement in performance, and any of the above analyzers may be used with ion detectors based on single-electron multipliers or, in the case of magnetic sectors, on arrays of multipliers, or, in the case of ion cyclotron resonance (ICR), on electric-field frequencies.  [c.195]

When quadrupole, hexapole, and other multipolar devices are operated in an RF-only mode, they act as guides, transmitting ions from one section of a mass spectrometer to another, offsetting the effects of space charge, stray electric fields, and collisions with neutral background molecules. The devices operate at atmospheric pressure or in high vacuum, serving as bridges between high-and low-pressure regions in a mass spectrometer.  [c.382]

Thermospray and plasmaspray can be used with both sector and quadrupole instruments. They have been used extensively to couple liquid chromatographs to mass spectrometers.  [c.392]

A simple mass spectrometer of low resolution (many quadrupoles, magnetic sectors, time-of-flight) cannot easily be used for accurate mass measurement and, usually, a double-focusing magnetic/electric-sector or Fourier-transform ion cyclotron resonance instrument is needed.  [c.416]

Mass spectrometer configuration. Multianalyzer instruments should be named for the analyzers in the sequence in which they are traversed by the ion beam, where B is a magnetic analyzer, E is an electrostatic analyzer, Q is a quadrupole analyzer, TOP is a time-of-flight analyzer, and ICR is an ion cyclotron resonance analyzer. For example BE mass spectrometer (reversed-geometry double-focusing instrument), BQ mass spectrometer (hybrid sector and quadrupole instrument), EBQ (double-focusing instrument followed by a quadrupole).  [c.430]

SIMS instruments are generally disdnguished by their primary ion beams, and the kinds of spectrometers they use to measure the secondary ions. Several types of primary ion beams—typically, oxygen, cesium, argon, or a liquid metal like gallium— are used in SIMS analyses, depending on the application. Nearly any SIMS instrument can be configured with one or more of these ion-beam types. The majority of SIMS mass spectrometers fall into three basic categories double-focusing electrostatic or magnetic sector, quadrupole, and time-of-flight. Time-of-flight analyzers are primarily used for surface and oiganic analyses (especially for high molecular weight species) and axe mentioned in the article on static SIMS.  [c.547]

Quadrupole spectrometers. These are the least expensive mass spectrometers, and the easiest to operate. By applying AC and DC potentials to a set of four rods, ions are separated by mass as they pass through the quadrupole. The voltages can be changed quickly, allowing relatively rapid scanning of the mass range, which is usually limited to around 1000 amu. Because quadrupoles cannot effectively separate ions having a wide energy spectrum, an electrostatic filter is used between the sample and the quadrupole. Perhaps the major drawback to  [c.551]

See pages that mention the term Quadrupole mass spectrometers : [c.321]    [c.622]    [c.90]    [c.282]   
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Surface and thin films analysis  -> Quadrupole mass spectrometers

Mass Spectrometry Basics (2003) -- [ c.205 , c.264 ]