A VUV photoionization aerosol time-of-flight mass spectrometer with a RF-powered VUV lamp for laboratory-based organic aerosol measurements

摘要

A vacuum ultraviolet (VUV) photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) has been developed for real-time, quantitative chemical analysis of organic particles in laboratory environments. Annozzle of similar to 0.12 mm orifice combined with an aerodynamic lens assembly and a three stage differential pumping system is used to sample particles at atmospheric pressure. The particles are vaporized on a thermal heater, and then the nascent vapor is photoionized by light generated with a RF-powered VUV lamp. A 0.41 V/cm electric field is used to drive the ions from the ionization region into the ion extraction region where a positive electric pulse repels the ions into a reflectron mass spectrometer. The mass resolution of the spectrometer is similar to 350 and the detection limit is similar to 400 mu m(3.). The signal intensities observed are linear with the mass concentration of aerosols. Oleic acid particles are well quantified with an uncertainty of 15% in mass concentrations ranging from 3.9 mg/m(3) to 392 mg/m(3). The VUV-ATOFMS has substantial potential for the use in laboratory investigations on organic aerosol chemistry.