DEVELOPMENT OF INSTRUMENTATION FOR PHOTOCHEMICAL STUDIES

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Spectral techniques such as fluorescence, phosphorescence, flash photolysis, and ESR are necessary to elucidate the photophysics and photochemistry of environmental chemicals. Because much of the needed equipment is either not available commercially or does not offer the desired futures, we build or modernize/upgrade most of it ourselves. This includes the interfacing to computers for ease of data acquisition and manipulation. Two old spectrophotofluorometers (steady state and phase modulation) that have been combined into one T-configured unit have being upgraded to measure phosphorescence spectra and photobleaching. The laser flash photolysis set-up has a new more powerful laser (Surelite II) for excitation. The choice of excitation wavelengths is extended from 400nm to the infrared by using a tunable OPO system that is pumped by the 355nm harmonic from the Surelite laser. A flow system that refreshes anaerobic samples after strong laser excitation has been added to the system, which prevents the bleaching of the irradiated area. This new laser flash photolysis set-up has been adapted for EMF studies by incorporating an electromagnet and a new analytical lamp to observe the transient spectra in the presence of EMF. The Surelite laser has also been aligned with the EPR spectrometer to generate radicals directly in the cavity of the EPR spectrometer after multi-photon absorption from laser pulses. Our singlet oxygen (1O2) spectrometers are being presently used to measure the interaction of singlet molecular oxygen with biological and environmental substrates we investigate. In addition, the steady-state 1O2 spectrophotometer is being upgraded to measure singlet oxygen production in non-photochemical reactions. To interpret the 1O2 phosphorescence data correctly, we have to establish how singlet oxygen properties may be affected by different environment. We have already measured the influence of polarity, proticity and polarizability in a number of solvents and solvent mixtures. Presently, these investigations are being extended to heterogeneous (micellar) systems, which more closely resemble biological environments.