Studies in Inverse Raman and Photothermal Deflection Spectroscopies.

Abstract

Applications of two laser spectroscopic techniques, inverse Raman spectroscopy and photothermal deflection spectroscopy, are described. Inverse Raman spectroscopy is used to study the intercalation of proflavin-DNA complex. Photothermal deflection spectroscopy is applied to the detection of chromatographic b and s in high performance thin layer chromatographic systems. The development of an instrument for this purpose is described. Resonance inverse Raman spectroscopy is used to probe the proflavin-DNA complex. A weak Raman hypochromic b and of proflavin is observed. The intensity is attenuated only some 20%. Other proflavin ring mode intensities parallel the absorption hypochromism and are attenuated to about 30% of their starting intensities. The 1485 cm('-1) b and is assigned to the Wilson 19a mode of the central ring of proflavin. Our study suggests that binding to DNA is localized on the outer rings. Photothermal deflection is used as the basis of a sensitive densitometer for thin layer chromatography. An argon ion laser delivering 20 mW is used as a source and a 2 mW He-Ne laser is used as a probe. The effect of beam shape on photothermal deflection densitometry is investigated. Measurement precision is about (+OR-) 1.5% under optimum performance. Detection limits for some quinones and a-ionone range from 1.3 ng to 6.2 pg, depending upon how strongly absorbing the compound is.