Development of portable single photon ionization time-of-flight mass spectrometer combined with membrane inlet

摘要

A homemade portable vacuum ultraviolet single photon ionization time-of-flight mass spectrometer (SPI-TOFMS) combined with a membrane inlet (MI) has been developed for the on-line monitoring of volatile organic compounds (VOCs) in environmental air. A description of the principle, configuration and key features of this MI-SPI-TOFMS is presented. A dimethylsiloxane (PDMS) membrane was used to concentrate the VOCs, and the vacuum ultraviolet (VUV) light (10.6 eV) for the ionization was generated by a commercial krypton lamp. A miniature reflectron TOF analyzer was used to make the instrument portable with quite high mass resolution (R = 450 at 106 amu). The limits of detection (LOD) of toluene and xylene can achieve 0.5 ppbv and 0.4 ppbv for 1 s measurement with scan frequency of 10 kHz, respectively. The dimension of the instrument is 30 cm × 20 cm × 20 cm with a total weight 13 kg without battery. The application of on-line monitoring air inside passenger cabin of brand new cars was shown in this paper.