![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
Abstract
During the hot application of bitumen-containing materials, as, for instance, in road paving and roofing, fumes are emitted which contain trace amounts of polycyclic aromatic compounds (PACs). The PAC levels are very low, and from the available epidemiological studies, there is no evidence that human exposure to bitumen or its fumes results in any cancer risk to the workforce. For comparative purposes we are trying to identify a laboratory “marker” for bitumen fume condensates (BFCs) which will give a correlation with biological activity and hence carcinogenic potential. Previously it was found that the determination of total 3–6-ring PACs by DMSO extraction followed by gas chromatographic analysis, whose use is well established for mineral oils, showed promise as a marker for BFCs as well.
Because standard DMSO extractions require about 4 g of sample, whereas generally only one mg or less of bitumen fume can be sampled, we developed a micro extraction technique, using Flow Injection Analysis (FIA). The FIA-DMSO extraction was coupled with normal phase liquid chromatography (NPLC) followed by gas chromatography with flame ionisation detection. Only 9 μl of sample solution in cyclohexane (at least 2% m/v) is injected into a cyclohexane stream and extracted with DMSO in the FIA coil. A 50 μl cut from the DMSO stream is introduced into a tetrahydrofurane (THF)/n-octane (50/50) stream to the NPLC-column. A 608 μl fraction of the THF/octane stream after the NPLC column, comprising the time window in which the standard EPA 2–6 ring PAC mixture elutes, is directly introduced into the retention gap. After evaporation of most of the solvent in the retention gap, the concentrated analyte is swept into the GC for the quantitative analysis using the FID. The system is selective towards the biologically most active fraction, the unsubstituted and lightly substituted PACs.
The 3–6-ring PAC content by FIA-DMSO correlates well with the Mutagenicity Index (MI) of the Mobil modified Ames test (R2= 0.927), these data have been measured on a wide range of materials ranging from bitumen fume condensates, distillate luboils to heavy residual materials such as bitumens. The residual products have to be freed from the heaviest molecules by pentane precipitation. The 3–6-ring PAC content also correlates with carcinogenicity in mouse skin-painting bioassays.
This technique enables us to assess the carcinogenic hazard of potential new feedstocks, processing routes and products in an early stage of development.