Quadrupole mass analyzer


Quadrupole mass analyzer

The quadrupole mass analyzer is one type of mass analyzer used in mass spectrometry. As the name implies, it consists of 4 circular rods, set perfectly parallel to each other.cite book|last=de Hoffmann|first=Edmond|coauthors=Vincent Stroobant|title=Mass Spectrometry: Principles and Applications|publisher=John Wiley & Sons, Ltd.|location=Toronto|date=2003|edition=Second|pages=65| isbn = 0471485667 ] In a quadrupole mass spectrometer the quadrupole mass analyzer is the component of the instrument responsible for filtering 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.

How it works


thumb|right|400 px|Image from "Apparatus For Separating Charged Particles Of Different Specific Charges" Patent number: 2939952 [">Cite patent|US|2939952 "Apparatus For Separating Charged Particles Of Different Specific Charges" Jun 1960; Paul et al.] The quadrupole consists of four parallel metal rods. Each opposing rod pair is connected together electrically and a radio frequency voltage is applied between one pair of rods, and the other. A direct current voltage is then superimposed on the R.F. voltage. Ions travel down the quadrupole in between the rods. Only ions of a certain m/z will reach the detector for a given ratio of voltages: other ions have unstable trajectories and will collide with the rods. This allows selection of a particular ion, or scanning by varying the voltages.

Applications

These types of mass spectrometers excel at applications where particular ions of interest are being studied because they can stay tuned on a single ion for extended periods of time. One place where this is useful is in liquid chromatography-mass spectrometry or gas chromatography-mass spectrometry where they serve as exceptionally high specificity detectors. Quadrupole instruments are often reasonably priced and make good multi-purpose instruments.

Triple quadrupoles

A linear series of three quadrupoles can be used; known as a triple quadrupole mass spectrometer. The first (Q1) and third (Q3) quadrupoles act as mass filters, and the middle (q2) quadrupole is employed as a collision cell. This collision cell is an RF only quadrupole (non-mass filtering) using He or N gas (~10-3 Torr, ~30 eV) to induce collisional dissociation of selected parent ion(s) from Q1. Subsequent fragments are passed through to Q3 where they may be filtered or scanned fully.

This process allows for the study of fragments (daughter ions) which are crucial in structural elucidation. For example, the Q1 may be set to "filter" for a drug ion of a known mass, which is fragmented in q2. The third quadrupole (Q3) can then be set to scan the entire "m/z" range, giving information on the sizes of the fragments made. Thus, the structure of the original ion can be deduced.

The arrangement of three quadrupoles was first developed by Jim Morrizon of LaTrobe University, Australia for the purpose of studying the photodissociation of gas-phase ions. Yet, the first triple-quadrupole for mass analysis was developed at Michigan State University by Dr. Christie Enke and graduate student Richard Yost in the late 1970's.

ee also

*RFQ Beam Coolers
*Quadrupole ion trap "A very closely related mass analyzer"
*Time of flight
*magnetic/electric sectors
*Fourier transform ion cyclotron resonance

References

External links

* [http://www.chem.vt.edu/chem-ed/ms/quadrupo.html Quadrupole mass spectrometry] Page from the Chemistry Hypermedia Project, summary of the technique and useful diagram


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Triple quadrupole mass spectrometer — Waters Quattro II triple quadropole mass spectrometer (center). This photo was taken in the old mass spec facility in Whitmore Lab of Pennsylvania State University. A triple quadrupole mass spectrometer is a tandem mass spectrometer consisting of …   Wikipedia

  • Mass spectrometry — (MS) is an analytical technique that measures the mass to charge ratio of charged particles.[1] It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical… …   Wikipedia

  • Mass spectrometry software — is software used for data acquisition, analysis, or representation in mass spectrometry. Contents 1 MS/MS peptide identification 1.1 Database search algorithms 1.1.1 SEQUEST 1.1.2 …   Wikipedia

  • Quadrupole ion trap — Scheme of a Quadrupole ion trap of classical setup with a particle of positive charge (dark red), surrounded by a cloud of similarly charged particles (light red). The electric field E (blue) is generated by a quadrupole of endcaps (a, positive)… …   Wikipedia

  • mass spectrometry — or mass spectroscopy Analytic technique by which chemical substances are identified by sorting gaseous ions by mass using electric and magnetic fields. A mass spectrometer uses electrical means to detect the sorted ions, while a mass spectrograph …   Universalium

  • Mass (mass spectrometry) — This article is about different concepts of mass used in mass spectrometry. For other uses, see mass. The mass recorded by a mass spectrometer can refer to different physical quantities depending on the characteristics of the instrument and the… …   Wikipedia

  • Mass spectrum — Electron ionization mass spectrum of toluene [4]. Note parent peak corresponding to molecular mass M = 92 (C7H8+) and highest peak at M 1 = 91 (C7H7+, quasi stable tropylium cation). A mass spectrum is an inten …   Wikipedia

  • Tandem mass spectrometry — Tandem mass spectrometry, also known as MS/MS, involves multiple steps of mass spectrometry selection, with some form of fragmentation occurring in between the stages. [IUPAC gold book definition of tandem mass spectrometer… …   Wikipedia

  • Secondary ion mass spectrometry — Infobox chemical analysis name = Secondary ion mass spectrometry caption =CAMECA IMS3f Magnetic SIMS Instrument acronym = SIMS classification =Mass spectrometry analytes = Solid surfaces, thin films related = Fast atom bombardment… …   Wikipedia

  • Static secondary ion mass spectrometry — Static secondary ion mass spectrometry, or static SIMS is a technique for chemical analysis including elemental composition and chemical structure of the uppermost atomic or molecular layer of a solid which may be a metal, semiconductor or… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.