Enhancement of Portable Mass Spectrometer Sensitivity and Selectivity by a Qualitative Pre-Scan Waveform (QPSW)

Abstract

While portability is a key aspect of small mass spectrometers, they also need to be able to effectively screen the analytes from complex matrices. The accuracy and performance of mass spectrometers depend not only on the identification of parent ion signals in targets but also fragment ion signals. This paper reports on the construction of a device that uses a new time-domain excitation waveform called qualitative pre-scan waveform (QPSW) for its quadrupole ion trap mass spectrometry analyzer. This approach uses scanning to eliminate interfering ions, thus improving the sensitivity for the analyte and removing the cumbersome steps required to convert conventional stored waveform inverse Fourier transform (SWIFT) waveforms from the frequency domain to the time domain. Tests show that the target ions can be fragmented just by introducing air at the moment when the pinch valve is opened without any need for a carrier gas. This simplifies the equipment required, making the mass spectrometer more portable. Tests were undertaken to compare the performance with the use of conventional SWIFT waveforms and to optimize its experimental parameters so that the target ions were effectively accumulated in the ion trap. An approximate 5-fold improvement in sensitivity was achieved by QPSW compared to the SWIFT for 2 μg/mL ketamine. A 5-fold reduction in the limit of detection (LOD) to 20 ng/mL was also obtained for enrofloxacin. In addition, the stability was improved by QPSW with a relative standard deviation less than 13% compared to 16% for SWIFT.

Keywords:

• mass spectrometry (MS)
• qualitative pre-scan waveform (QPSW)
• quadrupole ion trap (QIT)
• stored waveform inverse Fourier transform (SWIFT)

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (U20A20121 and 61971248), the Key Research and Development Program of Zhejiang Province (2020C03064), the Natural Science Foundation of Zhejiang Province (LY22F010004), the Ningbo Science and Technology Project) 2021S130), and the K.C. Wong Magna Fund at Ningbo University (xkzwl1507). It was also supported by the Natural Science Foundation of Zhejiang Province (LY21F020006), Ningbo Natural Science Foundation (2019A610088), the Ningbo Public Welfare Project (202002N3109), the Ningbo Key Science and Technology Plan (2025) Projects (2018B10075, 2019B10125, and 2019B10028), special research funding from the Marine Biotechnology and Marine Engineering Discipline Group at Ningbo University (No. 422004582), the Quzhou Science and Technology Planning Project (2020k06), and the Key Project of the National Natural Science Foundation of China (u20a20121).