摘要
A remarkable size dependency for sensitivity, which was considered to originate in dependence on absorption cross section, was observed in determinations with photoacoustic spectroscopy on 0.1-5.0 µm uniform polystyrene latex turbid solutions. A resonant increase In sensitivity appeared at a cross-sectional size coinciding with the excitation beam wavelength. Photoacoustic Immunoassay using the size dependency of sensitivity was proposed. In this method, antlbody/antigen coated latex particles agglutinated due to an Immunoreaction and the size of the agglutinations were controlled to be the same as the excitation wavelength. The agglutinations in a mixture of unreacted latex particles were selectively determined by photoacoustic spectroscopy and the antigen/antibody concentration was obtained. With a rheumatoid factor and denaturated γ-giobulin coated 0.2-µm polystyrene latex particles, the principle behind photoacoustic Immunoassay was proved and a determination limit of 9.8 X 10 IU/mL was obtained. This value was at least 3 orders better than results obtained by conventional turbidimetry. © 1987, American Chemical Society. All rights reserved.