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 has been 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 prevent 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 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 singlet oxygen spectrophotometer is being upgraded to measure singlet oxygen production in non-photochemical reactions. This system has also been modified to permit the direct observation of keratinocytes grown in a monolayer. With the aid of this instrumentation we have been able for the first time to detect singlet oxygen directly in cells. To interpret the singlet oxygen 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 over the heterogeneous (micellar) systems, which more closely relates to biological environments. As new technology becomes available, all of the above systems are continually being modified. These changes frequently also require the building of new interfaces and the development of new software for control. We are presently building a prototype photoconductivity cell to measure electrical photoconductivity in dielectric liquids in conjunction with ESR detection. This cell will be interfaced to the time-resolved laser flash photolysis spectrometer (vide supra) to permit studies of systems that cannot be observed optically. The laser flash photolysis system has been upgraded with a tunable laser system which emulates dye lasers. This new system has been adapted for EMF studies by incorporating an electromagnet.In order to understand the photochemistry and photophysics of environmental chemicals it is necessary to use the techniques of modern chemical analysis including spectroscopic techniques of many kinds. The object of this project is to build, test and interface spectrometers that are needed for photophysical studies.
