Electrochemiluminescent Determination of l-Cysteine with a Flow-Injection Analysis System

A flow-injection electrochemiluminescent method for l-cysteine determination has been developed based on its enhancement of the electrochemiluminecence of luminol at a glassy carbon electrode. This method is simple and sensitive for cysteine determination. Under the selected experimental parameters, the linear range for cysteine concentration was 1. 0 × 10–6–5. 0 × 10–5 mol/l, and the detection limit was 0. 67 µmol/l (S/N = 3). The relative standard deviation for 11 measurements of 1. 0 × 10–5 mol/l cysteine was 4. 5%. The proposed method has been applied to the detection of cysteine in pharmaceutical injections with satisfactory results.