Dependences of photoacoustic signal magnitude on thermal diffusion and solvent materials were examined for testing theoretical expressions for photoacoustic spectrometry in a liquid at normal incidence and oblique incidence (total internal reflection). As expected from the thermal diffusion term in the expressions, the signal magnitudes of opaque dye solutions increase with decreasing optical absorption coefficient in normal incidence and are nearly constant in oblique incidence. The signal magnitudes of dye solutions prepared from different solvents can be well explained for normal incidence by a solvent term in the expressions. However, some anomalous behavior of the signal magnitudes in oblique incidence seems to be due to adsorption of dye anions at a glass-solution interface.
The Japan Society for Analytical Chemistry