Lara A. Gundel

Direct Determination of the Phase Distributions of Semi-Volatile Polycyclic Aromatic Hydrocarbons Using Annular Denuders

An annular denuder-based sampler, here called the integrated organic vapor/particle sampler (IOVPS), has been developed for direct determination of both gaseous and particulate semi-volatile organic species. The IOVPS uses a cyclone inlet for removal of particles greater than 2.5 μm (D50) from the airstream, followed by two or three sandblasted glass annular denuders coated with ground particles of an adsorbent resin. The denuders trap the gas-phase species of interest before the airstream passes through a filter and a backup denuder. Extracts of the denuders and filters are analyzed for the semi-volatile species of interest. The IOVPS has been tested and validated for sampling semi-volatile polycyclic aromatic hydrocarbons (PAH) in indoor laboratory room air and environmental tobacco smoke (ETS). Ground XAD-4 was the adsorbent for these initial studies. Gas- and particulate-phase concentrations of semi-volatile PAH are presented for these two environments. The new sampler provides the means for directly determining phase distributions of PAH and other classes of semi-volatile organic species, rather than by difference or by techniques that are subject to large positive and negative artifacts.

Fractionation of polar organic extracts of airborne particulate matter using cyanopropyl-bonded silica in solid-phase extraction

A mg-scale fractionation method has been developed for polar organic matter in airborne particles. The method give reproducibly good recoveries of mass while avoiding the use of water or salts. Cyanopropyl-bonded silica solid-phase extraction (SPE) columns were used to fractionate a mixture of standard compounds and acetone-soluble extracts from particles collected in Elizabeth, NJ, USA and from National Institute of Standards and Technology Standard Material 1649 (urban air particles). Critical factors proved to be reducing the polarity of the extract before its application to the column and pre-wetting the column with n-hexane. Ten fractions were eluted with solvent mixtures of increasing polarity, ranging from n-hexane to methanol. Blank-corrected mass recoveries were 95 and 98% for the Elizabeth, NJ, USA and SRM 1649 extracts, respectively.

Characterization of particles from several sources and three urban areas by solvent extraction

Abstract Selective solvent extraction was used to characterize source and ambient particlulate matter collected during conditions of low photochemical activity, and the results were compared with those for samples collected during smog episodes. If the technique can correctly distinguish ozone-related, photochemically produced secondary compounds from primary (source) compounds, it should yield very different results for the two sampling conditions. The results of our comparison, however, indicate that selective solvent extraction is unable to uniquely identify the contribution of photochemical processes to the production of ambient particlulate matter.