In proper acid medium, colchicine could react with some aromatic amino acids such as tryptophane (Trp), tyrosine (Tyr) and phenylalanine (Phe) to form complexes, which led to fluorescence quenching of above amino acids, and the maximum quenching wavelengths were at 350 nm (Trp), 304 nm (Ty), 284 nm (Phe), respectively. Fluorescence quenching value (ΔF) was proportional to the concentration of colchicines in a certain range. Fluorescence quenching method for the determination of colchicine with Trp or Tyr as a probe had high sensitivity and the detection limits were 15.1 ng/mL (3.78×10^－8 mol/L) and 19.8 ng/mL (4.96×10^－8 mol/L) separately. The optimum conditions of the reaction, influencing factors and the effect of coexisting substances were investigated. The results showed that the selectivity was good, so the method could be used for the determination of colchicine. The composition of the complexes, the binding forces and binding mode were discussed in this work. Judging from the effect of temperature and the Stern-Volmer plots, the interaction was ascribed to a static quenching process. The association constants (K) were 9.7×10⁶ (COL-Trp), 8.9×10⁶ (COL-Tyr) and 6.3×10⁵ (COL-Phe), respectively. The forces occurring in the reaction mainly included the aromatic stacking interaction and hydrogen bonding interaction between COL and amino acid, and the aromatic stacking interaction was the primary reason for fluorescence quenching.

Key words: colchicine, tryptophane, tyrosine, phenylalanine, fluorescence quenching