Collision/reaction cell

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A collision/reaction cell is a device used in inductively coupled plasma mass spectrometry to remove interfering ions through ion/neutral reactions. [1]

Contents

Dynamic reaction cell

The collision reaction cell known by the trade name dynamic reaction cell was introduced by Perkin-Elmer on their Elan DRC (followed by Elan DRC II and Elan DRC-e) instrument. The dynamic reaction cell is a chamber placed before the traditional quadrupole chamber of an ICP-MS device, for eliminating isobaric interferences. [2] [3] [4] [5] The chamber has a quadrupole and can be filled-up with reaction (or collision) gases (ammonia, methane, oxygen or hydrogen), with one gas type at a time or a mixture of two of them, which reacts with the introduced sample, eliminating some of the interference.

The DRC is characterized by the following parameters, that can be modified: RPq (the corresponding q parameter from the Mathieu equation), RPa (the corresponding a parameter from the Mathieu equation), which refer to the voltage applied to the quadrupole rods and the gas flow of the reaction gas.

Ammonia gas is the best solution for the majority of interferences, but it is far for being the perfect gas. Sometimes, for specific isotopes, other gas must be used for better results or even mathematical correction, if no gas offers a satisfactory advantage.

Collisional reaction interface (CRI) or mini-Collision/Reaction Cell

The proprietary collisional reaction interface (CRI) [6] [7] used in the Bruker ICP-MS Aurora M90 destroying interfering ions. These ions are removed by injecting a collisional gas (He), or a reactive gas (H2), or a mixture of the two, directly into the plasma as it flows through the skimmer cone and/or the sampler cone. Supplying the reactive/collisional gas into the tip of the skimmer cone induces extra collisions and reactions that destroy polyatomic ions in the passing plasma. Fundamentally CRI is a mini- Collision/Reaction Cell installed in front of the parabolic Ion Mirror optics.

Axial field technology

Axial field technology (AFT) is a patented improvement of DRC made by Perkin-Elmer, which consists in two supplementary rods placed in the DRC cell, smaller than normal quadrupole's rods, with the purpose of "pushing" the ions faster to the exit by generating a supplementary electric potential, minimizing the time needed for the gas to be in the DRC and improving analysis speed. The suplimetary potential of the AFT rods does not contribute significantly to the global energy, but drastically improve ion passage time.

Collision cell technology with kinetic energy discrimination

Thermo Scientific's XSeries2 instrument utilizes a collision/reaction cell for interference removal, consisting of a non-consumable hexapole and chicane ion deflector, which takes the ion beam off-axis and leads to low instrument backgrounds of <0.5 integrated counts per second (icps) at vacant masses such as 5 and 220. This hexapole is inherently part of the Thermo lens system and is present in the ion path, regardless of the use of the collision cell. The collision/reaction gas mixtures can be 1% NH3 in He, 7% H2 in He and 100% H2, where the NH3 and H2 are reactive gasses and the He is a collisional gas. The 3rd generation cell utilizes kinetic energy discrimination, which employs running the quadrupole bias slightly less negative (more positive) than the hexapole bias. Polyatomic ions generated within the plasma can have larger atomic radii than analyte ions of similar mass, i.e. the interferent NaAr+ (mass 63) is larger than the analyte Cu+ (mass 63). Thus, when using a collisional/reactive gas mixture, these larger species undergo more collisions/reactions in the cell, in which they lose increasingly more energy, and are then excluded from the quadrupole mass filter by the kinetic energy barrier.

Octopole reaction system

Another implementation of this type of interference removal is an octopole (instead of a quadrupole) collision cell, implemented by Agilent's 7500 series. The octopole reaction system (ORS)) uses only helium or hydrogen and the volume of the cell is smaller than that of a DRC. The small molecules of helium and hydrogen collide with the large, unwanted polyatomic ions formed in the plasma and break them up into other ions that can be separated in the quadrupole mass analyser. However, unlike the DRC the OCR system is based only on collision reactions and not on chemical reactions.

Related Research Articles

Inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry that uses an Inductively coupled plasma to ionize the sample. It atomizes the sample and creates atomic and small polyatomic ions, which are then detected. It is known and used for its ability to detect metals and several non-metals in liquid samples at very low concentrations. It can detect different isotopes of the same element, which makes it a versatile tool in Isotopic labeling.

Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio of ions. The results are typically presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.

Ion source Device that creates charged atoms and molecules (ions)

An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.

A plasma afterglow is the radiation emitted from a plasma after the source of ionization is removed. The external electromagnetic fields that sustained the plasma glow are absent or insufficient to maintain the discharge in the afterglow. A plasma afterglow can either be a temporal, due to an interrupted (pulsed) plasma source, or spatial, due to a distant plasma source. In the afterglow, plasma-generated species de-excite and participate in secondary chemical reactions that tend to form stable species. Depending on the gas composition, super-elastic collisions may continue to sustain the plasma in the afterglow for a while by releasing the energy stored in rovibronic degrees of freedom of the atoms and molecules of the plasma. Especially in molecular gases, the plasma chemistry in the afterglow is significantly different from the plasma glow. The afterglow of a plasma is still a plasma and as thus retains most of the properties of a plasma.

Tandem mass spectrometry

Tandem mass spectrometry, also known as MS/MS or MS2, is a technique in instrumental analysis where two or more mass analyzers are coupled together using an additional reaction step to increase their abilities to analyse chemical samples. A common use of tandem-MS is the analysis of biomolecules, such as proteins and peptides.

Gas chromatography–mass spectrometry

Gas chromatography–mass spectrometry (GC-MS) is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. Applications of GC-MS include drug detection, fire investigation, environmental analysis, explosives investigation, and identification of unknown samples, including that of material samples obtained from planet Mars during probe missions as early as the 1970s. GC-MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, it can identify trace elements in materials that were previously thought to have disintegrated beyond identification. Like liquid chromatography–mass spectrometry, it allows analysis and detection even of tiny amounts of a substance.

Selected-ion flow-tube mass spectrometry

Selected-ion flow-tube mass spectrometry (SIFT-MS) is a quantitative mass spectrometry technique for trace gas analysis which involves the chemical ionization of trace volatile compounds by selected positive precursor ions during a well-defined time period along a flow tube. Absolute concentrations of trace compounds present in air, breath or the headspace of bottled liquid samples can be calculated in real time from the ratio of the precursor and product ion signal ratios, without the need for sample preparation or calibration with standard mixtures. The detection limit of commercially available SIFT-MS instruments extends to the single digit pptv range.

Chemical ionization Ionization technique used in mass [[spectroscopy]]

Chemical ionization (CI) is a soft ionization technique used in mass spectrometry. This was first introduced by Burnaby Munson and Frank H. Field in 1966. This technique is a branch of gaseous ion-molecule chemistry. Reagent gas molecules are ionized by electron ionization, which subsequently react with analyte molecules in the gas phase in order to achieve ionization. Negative chemical ionization (NCI), charge-exchange chemical ionization and atmospheric-pressure chemical ionization (APCI) are some of the common variations of this technique. CI has several important applications in identification, structure elucidation and quantitation of organic compounds. Beside the applications in analytical chemistry, the usefulness in chemical ionization extends toward biochemical, biological and medicinal fields as well.

Quadrupole mass analyzer

The quadrupole mass analyzer (QMS), also known as a transmission quadrupole mass spectrometer, quadrupole mass filter, or quadrupole mass spectrometer, is one type of mass analyzer used in mass spectrometry. As the name implies, it consists of four cylindrical rods, set parallel to each other. In a quadrupole mass spectrometer the quadrupole is the mass analyzer - the component of the instrument responsible for selecting sample ions based on their mass-to-charge ratio (m/z). Ions are separated in a quadrupole based on the stability of their trajectories in the oscillating electric fields that are applied to the rods.

Electron-capture dissociation

Electron-capture dissociation (ECD) is a method of fragmenting gas-phase ions for structure elucidation of peptides and proteins in tandem mass spectrometry. It is one of the most widely used techniques for activation and dissociation of mass selected precursor ion in MS/MS. It involves the direct introduction of low-energy electrons to trapped gas-phase ions.

Isotope-ratio mass spectrometry

Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample.

Proton-transfer-reaction mass spectrometry

Proton-transfer-reaction mass spectrometry (PTR-MS) is an analytical chemistry technique that uses gas phase hydronium reagent ions which are produced in an ion source. PTR-MS is used for online monitoring of volatile organic compounds (VOCs) in ambient air and was developed in 1995 by scientists at the Institut für Ionenphysik at the Leopold-Franzens University in Innsbruck, Austria. A PTR-MS instrument consists of an ion source that is directly connected to a drift tube and an analyzing system. Commercially available PTR-MS instruments have a response time of about 100 ms and reach a detection limit in the single digit pptv or even ppqv region. Established fields of application are environmental research, food and flavor science, biological research, medicine, security, cleanroom monitoring, etc.

Ion-mobility spectrometry–mass spectrometry

Ion-mobility spectrometry–mass spectrometry (IMS-MS), also known as ion-mobility separation–mass spectrometry, is an analytical chemistry method that separates gas phase ions based on their interaction with a collision gas and their masses. In the first step, the ions are separated according to their mobility through a buffer gas on a millisecond timescale using an ion mobility spectrometer. The separated ions are then introduced into a mass analyzer in a second step where their mass to charge ratios can be determined on a microsecond timescale. The effective separation of analytes achieved with this method makes it widely applicable in the analysis of complex samples such as in proteomics and metabolomics.

Atomic emission spectroscopy Analytical method using radiation to identify chemical elements in a sample

Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. The sample may be excited by various methods.

Triple quadrupole mass spectrometer

A triple quadrupole mass spectrometer (TQMS), is a tandem mass spectrometer consisting of two quadrupole mass analyzers in series, with a (non-mass-resolving) radio frequency (RF)–only quadrupole between them to act as a cell for collision-induced dissociation. This configuration is often abbreviated QqQ, here Q1q2Q3.

Linear ion trap

The linear ion trap (LIT) is a type of ion trap mass spectrometer. In a linear ion trap, ions are confined radially by a two-dimensional radio frequency (RF) field, and axially by stopping potentials applied to end electrodes. Linear ion traps have high injection efficiencies and high ion storage capacities.

Collision-induced dissociation A mass spectrometry technique to induce fragmentation of selected ions in the gas phase

Collision-induced dissociation (CID), also known as collisionally activated dissociation (CAD), is a mass spectrometry technique to induce fragmentation of selected ions in the gas phase. The selected ions are usually accelerated by applying an electrical potential to increase the ion kinetic energy and then allowed to collide with neutral molecules. In the collision some of the kinetic energy is converted into internal energy which results in bond breakage and the fragmentation of the molecular ion into smaller fragments. These fragment ions can then be analyzed by tandem mass spectrometry.

Extractive electrospray ionization

Extractive electrospray ionization (EESI) is a spray-type, ambient ionization source in mass spectrometry that uses two colliding aerosols, one of which is generated by electrospray. In standard EESI, syringe pumps provide the liquids for both an electrospray and a sample spray. In neutral desorption EESI (ND-EESI), the liquid for the sample aerosol is provided by a flow of nitrogen.

References

  1. ↑ Yip, Y.; Sham, W (2007). "Applications of collision/reaction-cell technology in isotope dilution mass spectrometry". TrAC Trends in Analytical Chemistry. 26: 727. doi:10.1016/j.trac.2007.03.007.
  2. ↑ V. Baranov; S. Tanner (1999). "A dynamic reaction cell for ICP-MS. Part 1: The rf-field energy contribution in thermodynamics of ion-molecule reactions". J. Anal. At. Spectrom. 14: 1133–1142. doi:10.1039/a809889a.
  3. ↑ S. Tanner; V. Baranov (1999). "A dynamic reaction cell for ICP-MS. Part 2: Reduction of interferences produced within the cell". J. Am. Soc. Mass Spectrom. 10: 1083–1094. doi:10.1016/S1044-0305(99)00081-1.
  4. ↑ "A beginner's Guide to ICP-MS R. Thomas". Archived from the original on 2018-08-08. Retrieved 2017-08-10.
  5. ↑ S. Tanner; V. Baranov; D. Bandura (2002). "Reaction cells and collision cells for ICP-MS: a tutorial review". Spectrochimica Acta B . 57: 1361–1452. Bibcode:2002AcSpe..57.1361T. doi:10.1016/S0584-8547(02)00069-1.
  6. ↑ I. Kalinitchenko, Patent Application under the Patents Cooperation Treaty WO 2004/012223 A1
  7. ↑ Wang, XueDong; Iouri Kalinitchenko. "Principles and performance of the Collision Reaction Interface for the" (PDF). Varian. Retrieved 2009-01-20.
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