Depth Profiling Analysis of Adsorbed Species on a Single Microparticle with Photoacoustic Spectroscopy

A novel nondestructive evaluation method for the adsorption layer thickness of a single microparticle using the frequency characteristics of the photoacoustic signal magnitude and phase is proposed. The adsorption thickness of metal 8-quinolinol chelates on an Amberlite XAD-2 microparticle of about 300 um in diameter was estimated by the proposed method. Measurements were performed with a single particle, and adsorption thicknesses of 10⁰ - 10¹ µm could be examined. A good agreement between the photoacoustic and microscopic determinations was obtained when the thermal diffusion length was longer than the adsorption thickness. The application range with respect to the relation between the thermal diffusion length and the adsorption thickness is discussed qualitatively on the basis of the experimental results of the frequency characteristics of the signal magnitude.