WHAT IT IS
Orbitrap Mass Spectrometry is a high-resolution, high-accuracy mass spectrometry technique that measures ion masses by detecting their orbital motion in an electrostatic field. It is part of the Fourier Transform (FT) mass spectrometry family and is widely used in proteomics, metabolomics, pharmaceutical analysis, environmental testing, and complex mixture characterization.
HOW IT WORKS
Ions are generated by electrospray ionization (ESI) or other soft ionization techniques and introduced into the Orbitrap analyzer after passing through ion optics and optional fragmentation stages such as collision-induced dissociation (CID) or higher-energy collisional dissociation (HCD).
Inside the Orbitrap analyzer, ions are trapped in an electrostatic field formed between a central spindle-shaped electrode and a surrounding outer electrode. The ions orbit around the central electrode and oscillate axially (back and forth along the central axis).
These oscillations generate an image current, which is detected over time. A Fourier transform (FT) is applied to this signal to convert it from the time domain into the frequency domain. The frequency of oscillation is directly related to the mass-to-charge ratio (m/z) of the ions, allowing their masses to be calculated with exceptional precision.
ADVANTAGES
Ultra-High Mass Resolution: Resolving powers exceeding 100,000 (and up to 1,000,000) allow the separation of closely spaced peaks, useful in isobaric compound analysis and isotope resolution.
High Mass Accuracy: Sub-ppm accuracy supports confident compound identification and exact mass confirmation without the need for extensive libraries.
Broad Mass Range: Suitable for detecting ions from small molecules to large proteins or oligonucleotides.
Stable and Compact Design: The electrostatic trapping system offers long-term stability without the need for superconducting magnets or cryogenic cooling.
MS/MS Capability: Can be combined with quadrupole or ion trap systems in hybrid instruments for tandem mass spectrometry experiments.
Quantitative Performance: Supports label-free quantitation, isotopic labeling, and targeted quantification in complex biological and chemical matrices.
CHALLENGES AND LIMITATIONS
Space Charge Effects: High ion populations can lead to decreased resolution and accuracy due to repulsion between ions (mitigated by AGC – automatic gain control).
Cost: Orbitrap systems are complex and relatively expensive, requiring specialized maintenance and operational expertise.
Limited High-Mass Performance: While capable of large molecule detection, performance may decline for very large ions or highly charged species.
Vacuum Requirements: Operates under ultra-high vacuum conditions, requiring robust system maintenance.