摘要
The optical beam deflection method, the sensitivity of which has been found to be higher for a smaller, single microparticle, is used for measuring the ultraviolet-visible absorption spectrum of a single microparticulate sample and for ultratrace determination of substances adsorbed on the microparticle. When an Ar ion laser of 11-mW output power is used as the excitation source, the detection limit of optical absorbance is 1.1 × 10 for a 50-μm-diameter microparticle, which corresponds to 28 fg of Fe-oxine chelate complex adsorbed on the microparticle. This sensitivity is about 2–3 orders of magnitude superior to that of a conventional absorption microspectrophotometric method. The absorption spectrum of a 50-μm-diameter resin microparticle adsorbing 20 pg of Feoxine complex can be obtained when an Xe lamp is used as the excitation source. Under this condition, the present method is still 1–2 orders more sensitive than the conventional absorption microspectrophotometric method. The optical beam deflection method is also applied to measure the absorption spectrum of a single human white blood corpuscle (5–15-μm size), and the spectral differences between leukemia and normal white blood corpuscles can be distinguished. © 1991, American Chemical Society. All rights reserved.