Differential Kinetic Spectrophotometric Determinations of Ascorbic Acid and L‐Cysteine by Partial Least Squares Method

Abstract

A kinetic spectrophotometric method was developed for simultaneous determination of ascorbic acid (AA) and L‐cysteine (Cys), based on detecting the colored final product. These compounds react differentially with Fe(III) in neutral medium, and the product of reduction, Fe(II), will form a colored compound with chromogenic reagent 1,10‐phenanthroline, which shows a maximum absorbance at 510 nm. The absorbance was measured at 510 nm every 2 sec from 10 to 190 sec, and the data obtained were processed by chemometric approach, partial least squares (PLS). The experimental calibration set was composed with 25 sample solutions using orthogonal calibration design for two component mixtures. The concentration ranges for AA and Cys were 2.00–11.82 and 1.50–14.99 ppm, respectively. The effect of pH and temperature was studied. The proposed method was successfully applied to the simultaneous determination of both analytes in pharmaceutical formulation.

Keywords:

• Ascorbic acid
• L‐Cysteine
• Partial least squares method
• Principal component regression