title: Real-time, ultrasensitive monitoring of air toxics by laser photoionization time-of-flight mass spectrometry.
abstract: Gas phase concentrations of individual polycyclic aromatic hydrocarbons (PAHs) were measured in real time in combustion products from a co-flow diffusion flame using laser photoionization (LP) time-of-flight mass spectrometry (TOF/MS). In particular, a naphthalene detection sensitivity of 4 parts per billion (ppb) was demonstrated. The use of calibration mixtures with argon indicated the feasibility of naphthalene detection at about 45 parts per trillion (ppt) at a signal-to-noise (S/N) ratio of 20. This suggests the possibility of low-ppt level detection at a S/N of 1. The novelty of the system is the use of a heated sampling probe and a continuously purged, heated-pulse valve that was positioned close to the ionization zone, thereby allowing the generation of photoions in the high-density region of the sample jet, where concentrations of PAH are high. Because the system developed allows for the real time detection of select species, it represents a useful tool in continuous emissions monitoring (CEM) for environmental compliance as well as direct process control.
authors.affiliation: Department of Chemical Engineering, University of California, Los Angeles, California, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Castaldi
authors.forename: S M
authors.initials: SM
authors.lastname: Senkan
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000633:toxicity*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis* / Q000633:toxicity*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000393:Air Pollutants; D011084:Polycyclic Aromatic Hydrocarbons