New Voltammetric Sensor Based on LDH and H2O2 for L-Proline Determination in Red and White Wines

Taking inspiration from our recent work in which a new sensor for hydrogen peroxide was proposed, our research group has now developed a simple, fast, and inexpensive voltametric system for determining proline concentration both in standard solutions and in real samples (red and white wines). This system uses a non-enzymatic sensor based on a working electrode of glassy carbon (GC) modified with a layered double hydroxide (LDH) compound, of the type GC-Ag-(paste)-LDH-H2O2, with hydrogen peroxide in solution at fixed concentration, in a three electrode cyclic voltammetry setup. Using an increasing concentration of standard solutions of L-proline, the method shows a linearity range, in semilogarithmic coordinates, between 125 mu mol L-1 and 3200 mu mol L-1 of proline, with a limit of detection (LOD) value of 85.0 mu mol L-1 and a limit of quantitation (LOQ) value of 95.0 mu mol L-1. The developed method is applied to the determination of proline in several samples of commercial Italian wines. The results are compared with those obtained by applying the classic spectrophotometric method of ninhydrin, obtaining a good correlation of the results.