Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Fourier transform ion cyclotron resonance

Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Fourier transform ion cyclotron resonance

Fourier rework ion cyclotron resonance mass spectrometry, also called Fourier rework mass spectrometry, is a kind of mass analyzer (or mass spectrometer) for figuring out the mass-to-charge ratio (m/z) of ions primarily based on the cyclotron frequency of the ions in a set magnetic discipline.[1] The ions are trapped in a Penning lure (a magnetic discipline with electrical trapping plates) the place they’re excited to a bigger cyclotron radius by an oscillating electrical discipline perpendicular to the magnetic discipline. The excitation additionally leads to the ions shifting in part (in a packet). The sign is detected as a picture present on a pair of plates which the packet of ions passes near as they cyclotron. The ensuing sign known as a free induction decay (FID), transient or interferogram that consists of a superposition of sine waves. The helpful sign is extracted from this knowledge by performing a Fourier rework to present a mass spectrum.

Fourier rework ion cyclotron resonance (FTICR) mass spectrometry is a really excessive decision method in that plenty might be decided with very excessive accuracy. Many functions of FTICR-MS use this mass accuracy to assist decide the composition of molecules primarily based on correct mass. That is attainable because of the mass defect of the weather. FT-ICR MS is ready to obtain greater ranges of decision than different types of mass spectrometry, partially, as a result of a superconducting magnet is way more secure than rf voltage.[2] One other place that FTICR-MS is helpful is in coping with complicated mixtures for the reason that decision (slim peak width) permits the indicators of two ions of comparable mass to cost (m/z) to be detected as distinct ions.[3][4][5] This excessive decision can be helpful in learning giant macromolecules comparable to proteins with a number of fees which might be produced by electrospray ionization. For instance, attomole stage of detection of two peptides has been reported .[6] These giant molecules include a distribution of isotopes that produce a collection of isotopic peaks. As a result of the isotopic peaks are shut to one another on the m/z axis, because of the a number of fees, the excessive resolving energy of the FTICR is extraordinarily helpful.

FTICR-MS differs considerably from different mass spectrometry methods in that the ions will not be detected by hitting a detector comparable to an electron multiplier however solely by passing close to detection plates. Moreover the plenty will not be resolved in house or time as with different methods however solely by the cyclotron (rotational) frequency that every ion produces because it rotates in a magnetic discipline. Thus, the totally different ions will not be detected in other places as with sector devices or at totally different instances as with time-of-flight devices however all ions are detected concurrently over some given time period. In FT-ICR MS, decision might be improved by growing the power of the magnet (in teslas) and by growing the magnet’s bore diameter.[7]

Historical past[edit]

FT-ICR was invented by Alan G. Marshall and Melvin B. Comisarow[8] on the College of British Columbia. The primary paper appeared in Chemical Physics Letters in 1974.[9] The inspiration was earlier developments in standard ICR and Fourier Rework Nuclear Magnetic Resonance (FT-NMR) spectroscopy. Marshall has continued to develop the method at The Ohio State College and Florida State College.

Linear ion lure – Fourier rework ion cyclotron resonance mass spectrometer (panels round magnet are lacking).

The physics of FTICR is just like that of a cyclotron not less than within the first approximation.

Within the easiest kind (idealized) the connection between the cyclotron frequency and the mass to cost ratio is given by:

the place f = cyclotron frequency, q = ion cost, B = magnetic discipline power and m = ion mass.

That is extra usually represented in angular frequency:

the place

ωc{displaystyle omega _{c}}

is the angular cyclotron frequency which is said to frequency by the definition

f=ω2π{displaystyle f={frac {omega }{2pi }}}


Due to the quadrupolar electrical discipline used to lure the ions within the axial route this relationship is just approximate. The axial electrical trapping leads to axial oscillations inside the lure with the (angular) frequency:

The place

α{displaystyle alpha }

is a continuing just like the spring fixed of a harmonic oscillator and depends on voltage and the lure dimensions and geometry.

The electrical discipline and the ensuing axial harmonic movement reduces the cyclotron frequency and introduces a second radial movement referred to as magnetron movement that happens on the magnetron frequency. The cyclotron movement continues to be the frequency getting used however the relationship above will not be precise because of this phenomenon. The pure angular frequencies of movement are:

the place

ωt{displaystyle omega _{t}}

is the axial trapping frequency due the axial electrical trapping and

ω+{displaystyle omega _{+}}

is the lowered cyclotron (angular) frequency and

ω{displaystyle omega _{-}}

is the magnetron (angular) frequency. Once more

ω+{displaystyle omega _{+}}

is what is often measured in FTICR. The which means of this equation might be understood qualitatively by contemplating the case the place

ωt{displaystyle omega _{t}}

is small, which is mostly true. In that case the worth of the novel is simply barely lower than

ωc/2{displaystyle omega _{c}/2}

and the worth of

ω+{displaystyle omega _{+}}

is simply barely lower than

ωc{displaystyle omega _{c}}

(the cyclotron frequency has been barely lowered). For

ω{displaystyle omega _{-}}

the worth of the novel is identical (barely lower than

ωc/2{displaystyle omega _{c}/2}

) however it’s being subtracted from

ωc/2{displaystyle omega _{c}/2}

leading to a small quantity equal to

ωcω+{displaystyle omega _{c}-omega _{+}}

(i.e. the precise quantity that the cyclotron frequency was lowered by).

ICR cell sorts[edit]

A cylindrical ICR cell. The partitions of the cell are product of copper, and ions enter the cell from the proper, transmitted by the octopole ion guides.

A overview of various cell geometries with their particular electrical configurations is on the market within the literature [10]. Nonetheless, ICR cells can belong to one of many following two classes.

Closed cells[edit]

A number of closed ICR cells with totally different geometries had been fabricated and their efficiency has been characterised. Grids had been used as finish caps to use an axial electrical discipline for trapping ions axially (parallel to the magnetic discipline strains). Ions might be both generated contained in the cell (by Electron impression ionization) or might be enjected to the cell from an exterior ionization supply (comparable to Electrospray or MALDI). Nested ICR cells with double pair of grids had been additionally fabricated to lure each constructive and detrimental ions concurrently.

Open cells[edit]

The commonest geometry is a cylinder, which is axially segmented into totally different components to supply totally different ring electrodes. The central ring electrode is mostly used for making use of radial excitation electrical discipline and detection. DC electrical voltage is utilized on the terminal ring electrodes to lure ions alongside the magnetic discipline strains. Open cylindrical cells with ring electrodes of various diameters have additionally been designed.[11] They proved not solely succesful in trapping and detecting each ion polarities concurrently, but in addition they succeeded to separate constructive from detrimental ions radially. This offered a big discrimination in kinetic ion acceleration between constructive and detrimental ions trapped concurrently inside the brand new cell. A number of ion axial acceleration schemes had been not too long ago written for ion-ion collision research [12]

Saved waveform inverse Fourier rework[edit]

Saved waveform inverse Fourier rework (SWIFT) is a technique for the creation of excitation waveforms for FTMS.[13] The time-domain excitation waveform is fashioned from the inverse Fourier rework of the suitable frequency-domain excitation spectrum, which is chosen to excite the resonance frequencies of chosen ions. The SWIFT process can be utilized to pick ions for tandem mass spectrometry experiments.


  1. Marshall, A. G.; Hendrickson, C. L.; Jackson, G. S., Fourier rework ion cyclotron resonance mass spectrometry: a primer. Mass Spectrom Rev 17, 1-35.
  2. Shi, S (2000). “Comparability and interconversion of the 2 commonest frequency-to-mass calibration features for Fourier rework ion cyclotron resonance mass spectrometry”. Worldwide Journal of Mass Spectrometry 195-196: 591. doi:10.1016/S1387-3806(99)00226-2. 
  3. Sleno L, Volmer DA, Marshall AG (February 2005). “Assigning product ions from complicated MS/MS spectra: the significance of mass uncertainty and resolving energy”. J. Am. Soc. Mass Spectrom. 16 (2): 183–98. doi:10.1016/j.jasms.2004.10.001. PMID 15694769. 
  4. Bossio RE, Marshall AG (April 2002). “Baseline decision of isobaric phosphorylated and sulfated peptides and nucleotides by electrospray ionization FTICR ms: one other step towards mass spectrometry-based proteomics”. Anal. Chem. 74 (7): 1674–9. doi:10.1021/ac0108461. PMID 12033259. 
  5. He F, Hendrickson CL, Marshall AG (February 2001). “Baseline mass decision of peptide isobars: a report for molecular mass decision”. Anal. Chem. 73 (3): 647–50. doi:10.1021/ac000973h. PMID 11217775. 
  6. Solouki T, Marto JA, White FM, Guan S, Marshall AG (November 1995). “Attomole biomolecule mass evaluation by matrix-assisted laser desorption/ionization Fourier rework ion cyclotron resonance”. Anal. Chem. 67 (22): 4139–44. doi:10.1021/ac00118a017. PMID 8633766. 
  7. Marshall, A (2002). “Fourier rework ion cyclotron resonance detection: ideas and experimental configurations”. Worldwide Journal of Mass Spectrometry 215: 59. doi:10.1016/S1387-3806(01)00588-7. 
  8. “UBC Chemistry Personnel: Melvin B. Comisarow”. College of British Columbia. Retrieved 2009-11-05. 
  9. M.B. Comisarow and A.G. Marshall, Chem. Phys. Lett. 25, 282 (1974)
  10. S. Guan, A. G. Marshall, Int. J. Mass Spectrom., 146/147 (1995) 261
  11. Kanawati, B. (2007). “Characterization of a brand new open cylindrical ion cyclotron resonance cell with uncommon geometry”. Evaluation of Scientific Devices 78: 074102. doi:10.1063/1.2751100. 
  12. Kanawati, B (2008). “Characterization of a brand new open cylindrical ICR cell for ion–ion collision research☆”. Worldwide Journal of Mass Spectrometry 269: 12. doi:10.1016/j.ijms.2007.09.007. 
  13. Cody, R. B. (1987). “Saved waveform inverse fourier rework excitation for acquiring elevated father or mother ion selectivity in collisionally activated dissociation: Preliminary outcomes”. Fast Communications in Mass Spectrometry 1: 99. doi:10.1002/rcm.1290010607. 

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