Ph.D Thesis

Ph.D StudentFisher Michal
SubjectOptical Methods for Chemical and Morphological
Charecterization of Polycyclic Aromatic
Hydrocarbon (PAH) Aerosols
DepartmentDepartment of Chemistry
Supervisor PROF. Israel Schechter


Analysis of polycyclic aromatic hydrocarbon (PAH) contaminated aerosols is of considerable environmental importance. These compounds, many of them known as carcinogenic or mutagenic agents, have to be continuously monitored in air. Due to their low vapor pressure they are most likely to be found in aerosols. The ideal aerosol instrument determines the size, composition and morphology of each particle sampled from a gas stream in real time. The ultimate goal of this research is to develop methods that would achieve, to best possible degree, all of these requirements. Four methods were developed:

a)Fourier transform spectral imaging microscopy (FT-SIM) was applied for fast analysis of aerosols contaminated with PAHs. Quantification limits in the range of 20 ng m‑3 in air were obtained.

b)      A new immunoassay for PAHs was developed and optimized. This study included the development of a competitive indirect enzyme-linked immunosorbent assay (ELISA) for PAHs and the development of an immunological-based fluorescent imaging analysis for intact PAH aerosols. Preliminary results indicated the feasibility of immunoassay analysis of PAH intact particulates.

c)Polymeric film sensors (PFS) were utilized for collection and detection of PAH aerosols. Direct analysis of PAH aerosols embedded into the PFS was performed by laser induced fluorescence (LIF) setup coupled with a dual-branch fiber-optic fluorescence probe. Identification and quantification was accomplished for both mono-component aerosols and for simple mixtures, with detection limits on the order of 10 ng cm3 in air. 

d)      Cavity ring-down laser absorption spectroscopy (CRLAS) was applied for aerosol detection and analysis. Validation of the method was performed using calibrated aerosol flows, such as NaCl, and CuCl2·2H2O, under ambient conditions. The actual sensitivity achieved by this preliminary setup was as low as an extinction coefficient of 5·10-8 cm-1. The ultimate theoretical performance of this method for aerosol detection is an extinction coefficient of 1·10-12 cm-1.