Carbonaceous aerosol components, OC and EC, were quantified using Nilotinib Desert Research Institute (DRI) Model 2001 carbon analyzer (Atmoslytic Inc., Calabasas, CA, USA). The IMPROVE-A thermal/optical reflectance (TOR) protocol (Chow et al., 2007a) was used for the analyses. The detailed analytical approach has been shown in Cao et al. (2005). Total OC was defined as the sum of four OC fractions plus OP, whereas total EC was defined as the sum of three EC sections minus OP. Han et al. (2009) used a thermal optical reflectance method to determine the concentrations of the char and soot fractions of EC because of their interest in the chemical, physical, and light absorbing properties of the two types of EC (Masiello, 2004 and Reid et al., 2005). Accordingly, char was defined here as EC1 minus OP and soot was calculated as the sum of EC2 and EC3.
In-injection port thermal desorption (TD) coupled with gas chromatography/mass spectrometry (GC/MS) was used to quantify selected PAHs and n-alkanes on the filter samples ( Ho and Yu, 2004, Chow et al., 2007b, Ho et al., 2008 and Ho et al., 2011). This method reduces sample preparation time, minimizes potential contamination, and offers lower detection limits compared with more conventional methods. In fact, the TD-GC/MS has become an alternative to a traditional method of solvent extraction (SE) followed by GC/MS ( van Drooge et al., 2009, Chow et al., 2007b and Bi et al., 2008). The details of in-injection port TD-GC/MS method have been described in our previous publications ( Ho and Yu, 2004, Ho et al., 2008 and Ho et al., 2011). Examples of selected ion monitoring (SIM) chromatograms of PAHs and n-alkanes in this study are shown in Fig. 2.