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

Irei S - Int J Anal Chem (2016)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Centre for Atmospheric Chemistry and Department of Chemistry, York University, 4700 Keels Street, Toronto, ON, Canada M3J 1P3.

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.

No MeSH data available.


Related in: MedlinePlus

Molecular structures of targeted hopanoid series and possible structures of their fragment ions.
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Related In: Results  -  Collection


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fig1: Molecular structures of targeted hopanoid series and possible structures of their fragment ions.

Mentions: A quarter piece of an 8 × 10 inch quartz fiber filter (Tissuequartz 2500 QAT-UP, Pall Corp., NY, USA) was spiked with the internal standards and extracted at 313 K for 16 hours with 100 mL of PRA grade dichloromethane (Sigma-Aldrich Canada, Oakville, ON, Canada) using Soxhlet apparatus (Sigma-Aldrich Canada). Volume of the extract was reduced to a few mL using a rotary evaporator (Büchi, New Castle, DE, USA). The concentrated extract was then filtered using a 2 mL gas-tight syringe (Hamilton, Reno, NV, USA) with a 0.45 mm PTFE syringe filter (Chromatographic Specialties, Inc., Brockville, ON, Canada) and transferred into a 5 mL Reacti-Vial (Pierce, IL, USA). The volume of the filtered extract was further reduced to ~0.2 mL under a gentle stream of pure nitrogen (Praxair Canada, Mississauga, Canada). A 5 μL of the concentrated extract was then directly analyzed by a gas chromatography-mass spectrometry or GC-MS (HP 5890 and 5972, Agilent Technology, USA). A surface-deactivated injection sleeve and glass wool (Siltek split/splitless sleeve and Siltek glass wool, Restek Corp., Bellefonte, USA) were used for the analysis. 5Sil-MS (0.25 mm i.d. × 30 m with 0.25 mm film thickness, Restek Corp.) was used as the separation column. At the injection, splitless injection mode was held for 1 min. Optimized GC temperature program for separation was as follows: the initial isothermal hold at 373 K for 0.1 min, then ramping temperature at rate of 5 K min−1 to 398 K with its isothermal hold for 3 min, and then ramping temperature at 5 K min−1 to 573 K with its isothermal hold for 8 min. Temperature for the injector and the interface between the GC and the MS was set to 573 K during the analysis. Flow rate of carrier gas, helium, was set to 1 mL min−1 continuously. Combination of scanning and selected ion monitoring (SIM) modes was used to identify and quantify the molecular markers. Mass-to-charge ratios (m/z) of the designated ions were chosen in a way that the molecular and fragment ions were unique (except those for n-alkanes) and the major ions in the mass spectra obtained by the standard analysis. The selected ions are listed in Table 1. It was found that the most of selected ions for PAHs were molecular ions (M+ and M2+ ions). For n-alkanes, the selected ions were C6H13+ and C7H15+. For the hopane series, the structures of parent molecules and fragment ions selected are shown in Figure 1. The structures of the fragment ions were based on Soares et al. [8]. The identification of the molecular markers was made by comparison with the retention time and the reference mass spectrum obtained by analysis of the chemical standards, as well as with NIST 98 mass spectrum library. As quality assurance, a reference standard mixture containing 100 ng mL−1 of each molecular marker referred to earlier was measured after the analysis of one sample extract.


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

Irei S - Int J Anal Chem (2016)

Molecular structures of targeted hopanoid series and possible structures of their fragment ions.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4834413&req=5

fig1: Molecular structures of targeted hopanoid series and possible structures of their fragment ions.
Mentions: A quarter piece of an 8 × 10 inch quartz fiber filter (Tissuequartz 2500 QAT-UP, Pall Corp., NY, USA) was spiked with the internal standards and extracted at 313 K for 16 hours with 100 mL of PRA grade dichloromethane (Sigma-Aldrich Canada, Oakville, ON, Canada) using Soxhlet apparatus (Sigma-Aldrich Canada). Volume of the extract was reduced to a few mL using a rotary evaporator (Büchi, New Castle, DE, USA). The concentrated extract was then filtered using a 2 mL gas-tight syringe (Hamilton, Reno, NV, USA) with a 0.45 mm PTFE syringe filter (Chromatographic Specialties, Inc., Brockville, ON, Canada) and transferred into a 5 mL Reacti-Vial (Pierce, IL, USA). The volume of the filtered extract was further reduced to ~0.2 mL under a gentle stream of pure nitrogen (Praxair Canada, Mississauga, Canada). A 5 μL of the concentrated extract was then directly analyzed by a gas chromatography-mass spectrometry or GC-MS (HP 5890 and 5972, Agilent Technology, USA). A surface-deactivated injection sleeve and glass wool (Siltek split/splitless sleeve and Siltek glass wool, Restek Corp., Bellefonte, USA) were used for the analysis. 5Sil-MS (0.25 mm i.d. × 30 m with 0.25 mm film thickness, Restek Corp.) was used as the separation column. At the injection, splitless injection mode was held for 1 min. Optimized GC temperature program for separation was as follows: the initial isothermal hold at 373 K for 0.1 min, then ramping temperature at rate of 5 K min−1 to 398 K with its isothermal hold for 3 min, and then ramping temperature at 5 K min−1 to 573 K with its isothermal hold for 8 min. Temperature for the injector and the interface between the GC and the MS was set to 573 K during the analysis. Flow rate of carrier gas, helium, was set to 1 mL min−1 continuously. Combination of scanning and selected ion monitoring (SIM) modes was used to identify and quantify the molecular markers. Mass-to-charge ratios (m/z) of the designated ions were chosen in a way that the molecular and fragment ions were unique (except those for n-alkanes) and the major ions in the mass spectra obtained by the standard analysis. The selected ions are listed in Table 1. It was found that the most of selected ions for PAHs were molecular ions (M+ and M2+ ions). For n-alkanes, the selected ions were C6H13+ and C7H15+. For the hopane series, the structures of parent molecules and fragment ions selected are shown in Figure 1. The structures of the fragment ions were based on Soares et al. [8]. The identification of the molecular markers was made by comparison with the retention time and the reference mass spectrum obtained by analysis of the chemical standards, as well as with NIST 98 mass spectrum library. As quality assurance, a reference standard mixture containing 100 ng mL−1 of each molecular marker referred to earlier was measured after the analysis of one sample extract.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Centre for Atmospheric Chemistry and Department of Chemistry, York University, 4700 Keels Street, Toronto, ON, Canada M3J 1P3.

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.

No MeSH data available.


Related in: MedlinePlus