Dynamic range of mass accuracy in LTQ orbitrap hybrid mass spectrometer

TLDR

The study investigates the dynamic range of accurate mass determination in short LC/MS experiments using a novel orbitrap mass spectrometer. They use a linear ion trap to load ions into a C‑trap, then inject them into an orbitrap analyzer where image‑current detection and FFT are performed within 1 s at 30,000 resolving power. The method yields ion populations spanning up to 10⁴ intensity range, achieving 5‑ppm mass accuracy with >95 % probability over a dynamic range exceeding 5 000—an order of magnitude better than TOF—and allows accurate mass determination when signal‑to‑noise exceeds ~2–3.

Abstract

Using a novel orbitrap mass spectrometer, the authors investigate the dynamic range over which accurate masses can be determined (extent of mass accuracy) for short duration experiments typical for LC/MS. A linear ion trap is used to selectively fill an intermediate ion storage device (C-trap) with ions of interest, following which the ensemble of ions is injected into an orbitrap mass analyzer and analyzed using image current detection and fast Fourier transformation. Using this technique, it is possible to generate ion populations with intraspectrum intensity ranges up to 10(4). All measurements (including ion accumulation and image current detection) were performed in less than 1 s at a resolving power of 30,000. It was shown that 5-ppm mass accuracy of the orbitrap mass analyzer is reached with >95% probability at a dynamic range of more than 5000, which is at least an order of magnitude higher than typical values for time-of-flight instruments. Due to the high resolving power of the orbitrap, accurate mass of an ion could be determined when the signal was reliably distinguished from noise (S/Np-p)>2...3).