|Ph.D Student||Levinson Jane-Evgenia|
|Subject||New Analytical Methods for Particulate Contaminants in|
|Department||Department of Chemistry||Supervisor||PROF. Israel Schechter|
|Full Thesis text|
Due to the growing interest in the quality of the environment new on-line monitoring technologies are highly encouraged. Our research is dedicated to the development of new methods applicable in on-line analysis of waterborne particles which is an important environmental object.
One of the known hazardous contaminants within the waterborne particles is the polycyclic aromatic hydrocarbons (PAHs). Nevertheless, this group of contaminants can not be properly sampled by the currently available sensors. A new setup for direct sampling and quantification of suspended particulate PAHs is suggested. It is based on a specially designed adsorbing film coupled to a fluorescence probe. As a part of the method optimization the electrokinetic properties of the PAHs hydrosols were utilized. Consequently, the electric field was applied which significantly induced the sampling rate of the PAH particles upon the film.
Another setup implemented for the PAH hydrosols measurements was Multi-Photon Ionization Fast-Conductivity system. The MPI response to the PAH of different concentration dispersed in a water was demonstrated. Two linear parts of the calibration plots with different slopes and the intersection point at the solubility limit of the PAH solution are the evidence for the transition between the solution and dispersion phases. Beyond the saturation limit of the PAH solution the process of the suspension development is observed and successfully traced by means of the MPI method. Supporting results were obtained by Fluorescence measurements supplying complimentary data interpreted in kinetic terms of the particles formation.
Laser Induced Breakdown technique was applied for hydrosols characterization. The Laser interaction with matter results in a breakdown process which brings to plasma formation. The spatial distribution of the induced plasma in suspensions was compared to that obtained in pure water. Such data were obtained from plasma imaging. The critical power density required for the breakdown induction is higher for liquid than for solid. This property is utilized for selective plasma generation upon the sols dispersed in a liquid. Another parameter that affects the breakdown threshold is the size of the particles suspension which is useful for size measurements. Both silica and polystyrene suspensions were examined. The results obtained with laser irradiation at 1064 nm were compared to those at 532 nm, and it was found that the laser wavelength affects the plasma imaging. Simultaneous sampling was performed by combining both wavelengths. The results indicate possible application of dichromatic system to compositional analysis of suspensions.