Characterization of asphalt fume composition under simulated road paving conditions by GC/MS and microflow LC/quadrupole time-of-flight MS

A highly sensitive, selective, and reliable analytical method has been deve loped and validated for characterization of asphalt fume generated under si mulated road paving conditions. A dynamic asphalt fume generation system wa s modified to provide consistent test atmospheres at simulated asphalt road paving conditions. In the process of fame generation, asphalt was initiall y preheated in an oven to 170 degreesC, pumped to a large kettle, which mai ntained the asphalt temperature between 150 and 170 degreesC, and then tran sferred to the generator. The fume was conducted from the generator to an e xposure chamber through a heated transfer line. Characterization of the asp halt fume test atmospheres included the following: (1) determination of the consistency of the asphalt aerosol composition within the generation syste m; (2) quantification of total organic matter of the asphalt fume by electr on impact ionization of isotope dilution gas chromatography/mass spectromet ry); and (3) identification of individual priority polycyclic aromatic hydr ocarbons (PAHs) in asphalt fume by selected ion monitoring. With the develo ped method, asphalt fumes could be characterized into three fractions: (1) filter collection of a large molecular size fraction over a range of mass-t o-charge (m/z) ratios of 173-309; (2) XAD-2 trapping of a medium molecular size fraction over a range of m/z ratios of 121-197; and (3) charcoal trapp ing of a small molecular size fraction that contained mainly the volatile v apor fraction over a range of m/z ratios of 57-141. Total organic matter of the asphalt fume was quantified over the 5 exposure days. Sixteen specific priority PAHs were monitored and identified. These PAHs were determined at trace levels on the filter fraction. A novel approach, which utilizes coll ision-induced dissociation of fragmentation pathway leading to a characteri stic fragmentation pattern by coupling microflow liquid chromatography to a tmospheric pressure chemical ionization of quadrupole time-of-flight mass s pectrometry, was used to fut-ther clarify the trace amount of key component s present in simulated road paving asphalt fumes. These results demonstrate that asphalt fume composition could be characterized and specific priority PAHs could be identified by this method. The major advantages of this meth od are its highly sensitivity, selectivity, and reliability for chemical ha zard characterization in a complex mixture. This method is suitable for sup port toxicity studies using simulated occupational exposure to asphalt fume s.