A novel segmented mass analyser with inductive mass-to-charge measurements of ions

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Abstract

Trapping mass spectrometers, such as Fourier transform ion cyclotron resonance and Orbitrap instruments, can obtain very high resolutions (~10^6 [1]), at the expense of having to trap ions for extended periods of time. This reduces cross-compatibility with chromatographic techniques such as ion mobility spectrometry, in which ion signal varies over milliseconds. Time-of-flight instruments operate on timescales in the order of 10 µs, however typically offer lower ultimate resolution due to constraints on ion path length in commercially viable devices. Furthermore, ToF devices use destructive detection methods, which can operate at single ion sensitivity - significantly more sensitive than ion trap mass analysers, which measure the (very small) image current induced in the device by ion motion. A device comprising segmented electrodes is proposed, which supports an Orbitrap-like electrostatic potential field spanning ~1.5 m axially to be used for mass-to-charge analysis of ions, using thin detector electrodes at the centre of ion oscillations to generate a strong, pulse-like induced signal, which can be used to elucidate the m/z of trapped ions. The proposed device is simulated in its entirety, using SIMION [2], to create the device and calculate the electrostatic potential, integrate ion trajectories, and measure induced signal; LTSPICE [3] to simulate transmission and amplification of the signal; and a proprietary program developed in C++ to process the signal. It is shown that the proposed device can reach resolutions of up to 250 000 in 5500 µs, and can reach resolutions of 15 000, with as few as 50 ions, in 3500 µs.

Keyword(s)

Fourier transform mass spectrometry (FTMS); High performance; High resolution; Ion trap; Mass spectrometry; Multipass; Orbitrap; Segmented; Time-of-flight

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