orbitrap

Orbitrap is a type of mass analyzer used in mass spectrometry. It operates by trapping ions in an electrostatic field between a central spindle electrode and an outer barrel, creating an axially oscillating ion cloud while ions orbit around the central axis. The motion induces an image current on the detection electrodes; the axial oscillation frequency of the ions is characteristic of their mass-to-charge ratio. Fourier transform of the detected signal produces a mass spectrum with high resolution and high mass accuracy.

Origin and development: It was developed in the early 2000s by Alexander Makarov and commercialized by Thermo Fisher Scientific, becoming widely used for proteomics and other omics analyses.

Performance and design: Orbitraps provide high resolving power and mass accuracy, with resolutions often exceeding 100,000 at m/z 400 and mass accuracies in the low ppm range. They operate under high vacuum and do not use magnetic fields, relying instead on electrostatic trapping fields. They can be used in single-stage MS or tandem MS modes when combined with collision-induced dissociation (CID) or higher-energy collisional dissociation (HCD) in hybrid configurations.

Variants and applications: Modern Orbitrap instruments integrate a quadrupole or linear ion trap for precursor selection and MS/MS, e.g., Orbitrap Q Exactive, Orbitrap Fusion, Orbitrap Exploris. They are widely used in proteomics, metabolomics, small molecule analysis, and complex mixtures due to their accuracy and throughput.

Limitations: instrumental cost, maintenance, and scanning speed can be limiting for some high-throughput workflows. The technology continues to evolve with improved scan rate and sensitivity.