A novel electrogenerated chemiluminescence sensing system for cystine determination based on its electrochemical parallel catalytic reaction

This paper describes a sensitive electrogenerated chemiluminescence (ECL) method for cystine determination with improved analytical characteristics based on the combination of electrochemical parallel catalytic reaction and chemiluminescence (CL) signal sensing. Cystine can be electrochemically reduced and gives a parallel catalytic wave effect in the presence of potassium persulfate. The reaction circulated on the electrode and the amount of the reduced product of the potassium persulfate was accumulated at the electrode surface. Then the reduced product of potassium persulfate reacts with fluorescein to emit a sensitive CL signal. Investigation of the characteristics of the electrochemical and chemiluminescence reactions revealed that the speed of the electrochemical reaction was much faster than that of the subsequent CL reaction, which proved the possibility of the combination of electrochemical parallel catalytic reaction with CL signal sensing. The ECL intensity is linearly related to the cystine concentration in the range from 60 nM to 8.0 μM.