The paper reports the simultaneous fluorescence determination of D,L-tryptophan enantiomer by chiral recognition of beta-cyclodextrin for the first time. Chiral discrimination is observed for fluorescence emission of D- and L-tryptophan when complexed to beta-cyclodextrin, and is significantly related to reaction temperature, time and pH. The proposed enantiomeric resolution of D-and L-tryptophan is based on the non-fluorescence emission of L-tryptophan in beta-cyclodextrin solution at 35 degrees C and after 24 h standing by. The fluorescence emission and absorbance of L-tryptophan disappear with the increase of beta-cyclodextrin at 35 degrees C and 24 h standing by, where as it is not observed for D-tryptophan. The detection limits are 3.1X10(-8) mol/L for D-tryptophan and 2.7X10(-7) mol/L for L-tryptophan, respectively, with a RSD of 1.0%-2.6% (n=7). The method has been shown to be accurate with a ratio of 2% (molar ratio) of one enantiomer in the presence of the other. The observed pseudo first-order rate constant is calculated. The reaction mechanism has been discussed using pyrene as a fluorescence probe.
