The
mass spectrometer is an important tool for modern chemical
analysis and detection. Especially, the emergence of miniature mass
spectrometers has provided new tools for field analysis and detection.
The resolution of a mass spectrometer reflects the ability of the
instrument to discriminate between adjacent mass-to-charge ratio ions,
and the higher the resolution, the better the discrimination of complex
mixtures. Quadrupole ion traps are generally considered as a low-resolution
mass spectrometry method, but they have gained wide attention and
development in recent years because of their suitability for miniaturization
and high qualitative capability. For an ion trap mass spectrometer,
the mass sensitivity and resolution can be mutually constrained and
need to be balanced by setting an appropriate scanning speed. In this
study, a super-resolution U-net algorithm (SR-Unet) is proposed for
ion trap mass spectrometry, which can estimate the possible ions from
the overlapping ion peaks of low-resolution spectra and improve the
equivalent resolution while ensuring sufficient sensitivity and analysis
speed of the instrument. By determining the mass spectra of a linear
ion trap mass spectrometer (LTQ XL) in Turbo and Normal scan modes,
the same unit mass resolution as that at a scan speed of 16,667 Da/s
was successfully obtained at 125,000 Da/s. Also, the experiments demonstrated
that the algorithm is capable of the mass-to-charge ratio and instrument
migration. SR-Unet can be migrated and applied to a miniature mass
spectrometer for cruise detection of volatile organic compounds (VOCs),
and the identification of VOC species in Photochemical Assessment
Monitoring Stations (PAMS) was improved from 31 to 50 species with
the same monitoring and analysis speed requirement. Further, super-unit
mass resolution peptide detection was achieved on a miniature mass
spectrometer with the help of the SR-Unet algorithm, which reduced
the full width at half-maxima (FWHM) of bradykinin divalent ions (m/z 531) from 0.35 to 0.15 Da at a scan
speed of 375 Da/s and improved the equivalent resolution to 3540.
The proposed method provides a new idea to enhance the field mixture
detection capability of miniature ion trap mass spectrometers.