| The separation of complex environmental mixtures in order to identify bioactive substances usually involves a multi-level scheme culminating in detailed chemical analysis. The approach of this research program involves a fractionation scheme which includes acid/base/neutral partitioning, silica gel column chromatography and two-stage HPLC separation. This separation scheme has been applied in the bioassay-directed search for major airborne mutagenic compounds on inhalable particulate matter. In other words, the biologically "hot" fractions are separated and analyzed chemically or subfractionated to isolate "hot" subfractions which are then chemically analyzed by gas chromatography/mass spectrometry (GC/MS), gas chromatography/negative chemical ionization mass spectrometry (GC/NCIMS), Fourier transform infrared (FTIR), high performance liquid chromatography (HPLC), Fluorescence and Diode Array UV. The mutagenicity assay involves the inactivated TA98 Salmonella strain (TA98-S9) as well as enzyme-activated (TA98+S9) strain. Some other assays containing TA98NR (TA98-nitroreductase deficient), TA98/1,8DNP{dollar}sb6{dollar} (TA98-dinitropyrene reductase deficient) and TA100+/{dollar}-{dollar}S9 strains have been also performed to detect the highly bioactive derivatives of polycyclic aromatic hydrocarbons (PAH). In essence, we are employing mutagenicity as our chromatographic detector to pinpoint the most bioactive fractions and compounds in the air which are assumed to be responsible for human health impact, and then identify them as well as assess their reactivity.; The comparison of winter, summer and fall samples indicates that the profiles are similar in these three periods. However, levels of polycyclic aromatic hydrocarbons (PAH) are significantly greater in winter as compared to summer and fall. The major mutagenic substances derived from PAH in airborne particulate matter are polar PAH derivatives and the higher contribution of these polar compounds in summer relative to winter and fall suggests that chemical and photochemical reactions during the warm season are important. |
