Haiyang Zheng

Particle size measurement system of the aerosol time-of-flight mass spectrometer optimization study

In this paper, Aerosol time-of-flight mass spectrometer optical particle size measurement system optimization and influencing factors are studied. Optimized the distance between nozzle and the skimmer, using a shorter wavelength light source measurement, Aerosol particle size measurement from the previous limit of 260 nm to 120 nm. Study found that the particles scattered light intensity is connected with light intensity and wavelength of the light source. particle size measurements using shorter laser wavelengths or greater energy, which can measure smaller size diameter within certain range. combining particle beam focusing aerodynamic lens system device, the particle size of air the time-resolved measurement of 256 / min, Measurement of time-resolved mass spectrometry to 170 / min, MS hit rate of 64.5%.

Initial Results of Continuous Monitoring of Dioxins Surrogate Using Laser Mass Spectrometry

Dioxins (polychiorinated dibenzo-p-dioxin/furan congeners) are the most toxic chemicals among the by-products emitted from combustion processes in trace amounts. Since the concentration of dioxins in flue gas is far beyond the detection limits of todays on-line methods the idea of using surrogate compounds of dioxins for fast measuring come up. Many evidences confirm that chlorobenzenes (monochlorobenze and some polychiorinated benzenes) are the suitable surrogates for on-line measuring of the dioxins in the flue gas by laser mass spectrometry. In this paper we present the principles of laser mass spectrometry. The 1+1 two-photon Resonant Enhanced Multiphoton Ionization (REMPI) spectra of monochlorobenzene in the range 240≈250nm are studied. The measurement shows that monochlorobenzene has the highest ionization efficiency excited at 248.6nm in this wavelength range and the detection limit of monochlorobenzene at ppb(v/v) concentration is obtained. The REPMI-MS properties of monochlorobenzene in this wavelength range provide useful information of practical measurements on mixtures.