Flow-Injection Simultaneous Chemiluminescence Determination of Ascorbic Acid and L-Cysteine with Partial Least Squares Calibration

In this paper, a flow-injection chemiluminescence system is proposed for simultaneous determination of ascorbic acid and L-cysteine with partial least squares calibration. This method is based on the fact that both AA and Cys can quantitatively reduce Fe³⁺ to Fe²⁺, and that the reaction rates of AA and Cys with Fe³⁺ are different. The reduced product Fe²⁺ was detected with the luminol-Fe²⁺–O₂ CL system. The CL intensity was measured and recorded at different reaction times of Fe³⁺ with AA and Cys, and the obtained data was processed by the chemometric approach of partial least squares. The experimental calibration set was composed of 16 sample solutions using an orthogonal calibration design for two component mixtures. The calibration curve was linear over the concentration range of 0.066µgmL^–1 and 0.440µgmL^–1 for ascorbic acid and L-cysteine, respectively. The proposed method was successfully applied to the simultaneous determination of both analytes in pharmaceutical formulations and human urine samples.