Direct Analysis of Low-Volatile Molecular Marker Extract from Airborne Particulate Matter Using Sensitivity Correction Method

Abstract

Molecular marker analysis of environmental samples often requires time consuming preseparation steps. Here, analysis of low-volatile nonpolar molecular markers (5-6 ring polycyclic aromatic hydrocarbons or PAHs, hopanoids, and n-alkanes) without the preseparation procedure is presented. Analysis of artificial sample extracts was directly conducted by gas chromatography-mass spectrometry (GC-MS). After every sample injection, a standard mixture was also analyzed to make a correction on the variation of instrumental sensitivity caused by the unfavorable matrix contained in the extract. The method was further validated for the PAHs using the NIST standard reference materials (SRMs) and then applied to airborne particulate matter samples. Tests with the SRMs showed that overall our methodology was validated with the uncertainty of ~30%. The measurement results of airborne particulate matter (PM) filter samples showed a strong correlation between the PAHs, implying the contributions from the same emission source. Analysis of size-segregated PM filter samples showed that their size distributions were found to be in the PM smaller than 0.4 μm aerodynamic diameter. The observations were consistent with our expectation of their possible sources. Thus, the method was found to be useful for molecular marker studies.

Molecular Marker Study of Particulate Organic Matter in Southern Ontario Air

“…Here we analyzed the filter samples for the following nonpolar substances to trace primary POM: polycyclic aromatic hydrocarbons (PAHs) of benzo[a]pyrene (BaP), dibenz[a,h]anthracene (Db), indeno[1,2,3-cd]pyrene (Ind), benzo[ghi]perylene (BgP), and coronene (Cor) (purities > 99%, Sigma-Aldrich Canada, Oakville, ON, Canada); hopane series of trisnorhopane (TrisHp), norneohopane (NorHp), α , β -hopane (abHp), and β , α -hopane (baHp) (purities > 99%, Chiron AS, Norway); and n -alkanes with the carbon numbers from C 20 to C 34 (purities > 99%, Sigma-Aldrich Canada). The details of the nonpolar molecular marker analysis are described elsewhere [ 21 ]. Briefly, one or two pieces of each filter sample, which 40 and 200 ng of internal standards (benzo[a]pyrene-d 2 and tetracosane-d 50 , Sigma-Aldrich Canada) were spiked onto, were extracted with 100 mL of PRA grade dichloromethane (Sigma-Aldrich Canada) using Soxhlet apparatus (Sigma-Aldrich Canada) for 16 hours.…”

“…However, the detailed analysis ( F -test of one-sided analysis of variance) on slopes of the linear regressions for each site and concentration ratios of two species for each sample revealed that some PAHs showed statistically the same trend (or concentration ratios) at all three sites, but some did not. For example, concentration plots of BaP versus Ind [ 21 ] exhibited a high correlation, and the calculated F -value was 0.664. For the total number of 46 data points obtained from the three locations, the α threshold of 5% confidence interval for the null hypothesis is 3.2, which is apparently higher than the calculated F -value, justifying that the data from the three locations can be handled together.…”