Health Assessment Document for Diesel Emissions - NSCEP | US ...
Health Assessment Document for Diesel Emissions - NSCEP | US ...
Health Assessment Document for Diesel Emissions - NSCEP | US ...
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1 solvent. and this ratio was probably the result of the presence of both oxygenated organic<br />
2 compounds and inorganic sulfates in the extracted mass.<br />
3<br />
4 2.3.2.3.1. Extraction and fractionation techniques. A variety of solvents and extraction<br />
5 techniques have been used in the past <strong>for</strong> the separation of organic compounds from diesel<br />
6 particles (Levsen, 1988). Although the reports on the extraction efficiencies are in part<br />
7 contradictory, it appears that Soxhlet extraction and the binary solvent system composed of<br />
8 aromatic solvent and alcohol gave the best recovery ofPAHs, as determined by 14C-B[a]P . 9 (benzo[ a ]pyrene) spiking experiments (Schuetzle and Perez, 1981 ). Direct chemical analysis of<br />
1 0 the entire extractable fraction of diesel particulate matter is not generally possible because a large<br />
11 number of compounds of different polarity_ are present. The separation of diesel particulate<br />
12 organic matter (POM) into various fractions according to chemical functionalities is a necessary<br />
13 preliminary step to chemical identification of individual compounds. Open-column liquid<br />
14 chromatography (LC) and liquid-liquid separation procedures have been the most widely used<br />
15 fractionation methods (Lee and Schuetzle, 1983). Open-column LC is very often followed by<br />
16 normal-phase high-per<strong>for</strong>mance liquid chromatography (HPLC) if the identification of less<br />
17 abundant components is required.<br />
18<br />
19 2.3.2.3.2. Chemical composition. Table 2-7 lists the general classes of extractable organic<br />
·20 compounds identified in POM from combustion emissions, including diesel emissions.<br />
21 Liquid chromatography methods usually divide the complex environmental mixtures of<br />
22 organic compounds ·into nonpolar, moderately polar, and polar fractions. This separation is<br />
Table 2-7. Classes of organic compounds identified in particulate-phase<br />
combustion emissions<br />
Hydrocarbons<br />
Derivatives• of hydrocarbons<br />
Polycyclic aromatic hydrocarbons (PAHs)<br />
Derivatives of PAH<br />
Multifunctional derivatives of P AH<br />
Heterocyclic compounds<br />
Derivatives of heterocyclics<br />
Multifunctional derivatives of heterocyclic compounds<br />
'Derivatives include acids, alcohols, aldehydes, esters, ketones, nitrates, and sulfonates.<br />
Source: Adapted from Schuetzle ( 1988).<br />
2/1198 2-18 DRAFT--DO NOT CITE OR QUOTE<br />
. .