Mass Spectrometry Handbook

The conceptual design of the O-trap Fourier transform ion cyclotron resonance (FT-ICR) cell addresses the speed of analysis issue in FT-ICR mass spectrometry. The concept of the O-trap includes separating the functions of ion excitation and detection between two different FT-ICR cell compartments. The detection compartment of the O-trap implements additional internal coaxial electrodes around which ions with excited cyclotron motion revolve. The expected benefits are higher resolving power and the lesser effect of the space charge. In this work we present the first experimental demonstration of the O-trap cell and its features, including the high ion transfer efficiency between two distinct compartments of an ICR cell after excitation of the coherent cyclotron motion. We demonstrate that utilization of the multiple-electrode detection in the O-trap provides mass resolving power enhancement (achieved over a certain time) equal to the order of the frequency multiplication. In an O-trap installed in a 5 T desk-top cryogen-free superconducting magnet, the resolving power of R = 80,000 was achieved for bradykinin [M + 2H](2+) (m/z 531; equivalent to 100,000 when recalculated for m/z 400) in 0.2 s analysis time (transient length), and R = 300,000 at m/z 531 for a 1 s transient. In both cases, detection on the third multiple of the cyclotron frequency was implemented. In terms of the acquisition speed at fixed resolving power, such performance is equivalent to conventional FT-ICR detection using a 15 T magnet.

Section: Novel Aspects Of the O-trap Ft-icr Cellmentioning

confidence: 99%

Fourier transform ion cyclotron resonance mass spectrometer with coaxial multi‐electrode cell (‘O‐trap’): first experimental demonstration

Misharin

Zubarev

Doroshenko

2010

“…Gabrielse implemented this approach by inserting compensation rings into an open cylindrical cell. [7] This idea was recently used in FTICR cells by Tolmachev et al [8] and Brustkern et al [9] Other segmentation methods involve a matrix cell by Marshall's group [10] and the segmented cells developed by Bruce et al [11] and Barlow and Tinkle [12] at Pacific Northwest National Laboratory (PNNL). All these harmonization methods provide a hyperbolic electric field only in a region around the center of the cell.…”

mentioning

confidence: 99%

Fourier transform ion cyclotron resonance cell with dynamic harmonization of the electric field in the whole volume by shaping of the excitation and detection electrode assembly

Boldin

Nikolaev

2010

110

119

A new principle of formation of the effective electric field distribution in a Penning trap is presented. It is based on the concept of electric potential space averaging via charged particle cyclotron motion. The method of making hyperbolic-type field distribution in the whole volume of a cylindrical Penning trap is developed on the basis of this new principal. The method is based on subdividing the cell cylindrical surface into segments with shapes producing quadratic dependence on axial coordinate of an averaged (along cyclotron motion orbit) electric potential at any radius of cyclotron motion. The cell performance is compared in digital experiments with the performance of a Gabrielse-type cylindrical cell with four compensation electrodes and is shown to be more effective in ion motion harmonization at higher cyclotron radii and axial oscillation amplitude.

“…It is crucial for assigning unknown spectra and quantifying isotopically labeled molecules. [1][2][3] Fourier transform mass spectrometry (FTMS) instruments have resolving powers in the 10 5 to 10 7 range [4][5][6] and thus can resolve the isotopic fine structure of molecules, including biomolecules such as proteins and lipids. This enables small differences in the elemental compositions of large molecules to be detected.…”

mentioning

confidence: 99%

Memory‐efficient calculation of the isotopic mass states of a molecule

Karabacak

Cobb

et al. 2010

Our previous work postulated a transition concept among different isotopic mass states (i.e., isotopic species) of a molecule, and developed a hierarchical algorithm for accurately calculating their masses and abundances. A theoretical mass spectrum can be generated by convoluting a peak shape function to these discrete mass states. This approach suffers from limited memory if a level in the hierarchical structure has too many mass states. Here we present a memory efficient divide-and-recursively-combine algorithm to do the calculation, which also improves the truncation method used in the previous hierarchical algorithm. Instead of treating all of the elements in a molecule as a whole, the new algorithm first 'strips' each element one by one. For the mass states of each element, a hierarchical structure is established and kept in the memory. This process reduces the memory usage by orders of magnitude (e.g., for bovine insulin, memory can be reduced from gigabytes to kilobytes). Next, a recursive algorithm is applied to combine mass states of elements to mass states of the whole molecule. The algorithm described above has been implemented as a computer program called Isotope Calculator, which was written in C++. It is freely available under the GNU Lesser General Public License from http://www.cs.brandeis.edu/~hong/software.html or http://people.brandeis.edu/~agar.