Abstract: In pH=6.6 Britton-Robinson(BR) buffer medium, a 1: 2(molar ratio) compound of dichlorofluorescein(DCF), dibromofluorescein(DBF) or diiodofluorescein(DIF) with carbazochromum(CBZC) was formed by electrostatic attraction, aromatic stacking interaction and van der Waals’ force, which led to fluorescence quenching of above halide fluorescein dyes, and the maximum quenching wavelength were located at 533 nm(DCF), 536 nm(DBF) and 560 nm(DIF), respectively. Fluorescence quenching value(ΔF) is proportional to the concentration of CBZC in a certain range. Fluorescence quenching method for the determination of CBZC has high sensitivity, detection limits are 3.3 ng/mL(CBZC-DCF system), 5.7 ng/mL(CBZC-DBF system) and 129.6 ng/mL(CBZC-DIF system), respectively. The effect of coexisting substances, the optimum conditions of the reaction and influencing factors were investigated. The results show this method has good selectivity. This method was successfully applied to the quick determination of CBZC in serum and urine samples. Judging from the effect of temperature, fluorescence lifetime determination and the Stern-Volmer plots, the quenching of fluorescence is a static quenching process.

Key words: Dichlorofluorescein, Dibromofluorescein, Diiodofluorescein, Carbazochromum, Fluorescence quenching