Catalytic kinetic spectrofluorimetric determination of L-cysteine

A catalytic spectrofluorimetric method was proposed for the determination of trace L-cysteine.It was based on the catalytic effect of L-cysteine on the oxidation of Brilliant cresyl blue by potassium bromate in chlorhydric acid(HCl)-potassium chloride(KCl) buffer solution.The operation conditions and the effect of some potential interferences on the fluorescent properties of L-cysteine were also investigated.The detection limit for L-cysteine was 0.01 μg/mL,and the linear range of the determination was 0.032～1.60 μg/mL,RSD5.7%.It was used to determine trace L-cysteine in syrup and honey.The recoveries were between 99.3% and 104.0%.The results were satisfactory.