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

Abstract

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 μmol L−1 and 3200 μmol L−1 of proline, with a limit of detection (LOD) value of 85.0 μmol L−1 and a limit of quantitation (LOQ) value of 95.0 μmol 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.

A Direct Catalytic Ethanol Fuel Cell (DCEFC) Modified by LDHs, or by Catalase-LDHs, and Improvement in Its Kinetic Performance: Applications for Human Saliva and Disinfectant Products for COVID-19

“…To obtain the (Zn II ,Al III (OH) 2 ) + NO 3 − ·H 2 O LDHs type, hereinafter also written several times as (Zn–Al–NO 3 ), in this work, we used the co-precipitation method for the synthesis of LDHs, described in more detail in our previous works [ 11 , 12 ]. Briefly, to carry out the synthesis of LDH of the type (Zn-Al-NO 3 ): 50 mmol L −1 of aluminum nitrate and 150 mmol L −1 of zinc nitrate were dissolved in 200 mL of distilled and deionized water.…”

“…In recent years, a certain number of studies, based on LDHs of the type (Zn II ,Al III (OH) 2 ) + NO 3 − ·H 2 O, were conducted by our research group, obtaining good results, especially from an analytical point of view [ 9 , 10 , 11 , 12 ]. Furthermore, encouraging results have been obtained, both analytical, e.g., on alcoholic drinks, beverages [ 13 , 14 , 15 ], drugs, or pharmaceutical formulations [ 16 , 17 , 18 , 19 , 20 , 21 ], and also for energy purposes with the use of glucose and carbohydrates [ 15 , 22 ] by means of a simple and inexpensive DCEFC.…”