Abstract: Room temperature phosphorescence(RTP) signal intensity of eosin-ITC on a polyamide membrane(PM) was very low, but the signal was increased obviously once some inorganic salts were added into the system at λ_ex/λ_em=532 nm/685 nm. The enhancement effect of ⅡA element ions(such as Ca ²⁺, Sr ²⁺ and Ba ²⁺) on RTP of eosin-ITC is much obvious than that of Pb ²⁺ and Hg ²⁺ used constantly as an outer heavy atom perturber in phosphorimetry. Based on that, a new solid substrate room temperature phosphorescence immunoassay(SS-RTP-IA) for the determination of the human IgG was proposed to demonstrate the feasibility using eosin-ITC as phosphorescent marker. It was found that a good linear relationship with the ΔI_P was obtained when the amount of human IgG in the range from 6.25 to 400 pg/spot(corresponding to the mass concentration: 15.63 ng/mL—1 μg/L, sample volume of 0.4 μL/spot). The regression equation of working curve can be expressed as ΔI_P=3.06²⁺0.00864x(pg)(n=7, r=0.996), The detection limit calculated as 3S_b/k is 0.394 pg/spot. The method was applied directly to the determination of IgG in human serum with a satisfying result. These results show that eosin-ITC can be used conveniently as a RTP marker of high sensitivity.

Key words: Solid substrate room temperature phosphorescence immunoassay, Eosin-5-isothiocynate, CaCl₂ as an enhancer, IgG