Electrochemical determination of L-tryptophan in food samples on graphite electrode prepared from waste batteries

Abstract

One of the goals of this research was to develop an electrochemical sensor that had the ability to determine the target analyte and was both cheap and non-toxic. Another goal was to influence the reduction of electronic waste. In accordance with these, a graphite rod from zinc-carbon batteries was used to prepare an electrochemical sensor for the determination of L-tryptophan in Britton–Robinson buffer solution. Two electrochemical methods were used in the experimental research, differential pulse voltammetry and cyclic voltammetry. The effect of different parameters, including the pH value of supporting solution, scan rate, as well as the concentration of L-tryptophan on the current response, was studied. The pH value of Britton–Robinson buffer influenced the intensity of L-tryptophan oxidation peak, as well as the peak potential. The intensity of the current response was the highest at pH 4.0, while the peak potential value became lower as the pH increased, indicating that protons also participated in the redox reaction. Based on the obtained data, electrochemical oxidation of L-tryptophan at the graphite electrode was irreversible, two electron/two proton reaction. In addition, it was observed that the oxidation peak increased as the scan rate increased. According to the obtained electrochemical data, it was suggested that the oxidation of L-tryptophan was mixed controlled by adsorption and diffusion. The linear correlation between oxidation peak and L-tryptophan concentration was investigated in the range 5.0–150.0 µM and the obtained values of limit of detection and limit of quantification were 1.73 µM and 5.78 µM, respectively. Also, the prepared electrochemical sensor was successful in determination of target analyte in milk and apple juice samples.

Using a Boron‐Doped Diamond Electrode in Anionic Surfactant Media as an Improved Electrochemical Sensor for the Anticancer Drug Ibrutinib

“…The fact that the value of this slope is close to the theoretical value of 59 mV/pH indicates that the number of protons and electrons is equal in the oxidation reaction mechanism of IBR in an aqueous solution. [39] Moreover, the intersection point of the obtained lines corresponds to the pK a value of the compound approximately. Possible ionization states of a pharmaceutical can be understood by its dissociation constant, pK a .…”

Oxidation Mechanism of 1‐Methyl‐tryptophan and Tryptophan on Glassy Carbon Electrode: A Comparative Study

“…Our interest in the electroanalysis of Trp using DPV at GCE comes from a large number of works on modified GCEs [14][15][16][17]. To our knowledge there is no analytical data available for oxidation of Trp on GCEs, such as limit of detection, sensitivity and the range of linear response.…”

“…This occurs in two successive irreversible pH-dependent steps: a first stage with the formation of 2-oxyindolalanine; and a second step where this is electro-oxidized to form two electroactive products (quinone derivatives) [23]. Several electroanalytical methodologies with low detection limits, using modified electrodes, mainly with nanostructures, have been explored for the quantification of Trp [14][15][16][17]. However, to our knowledge so far, no work has quantified Trp on the bare GCE, without modification; and no comparison parameter in relation to the modified electrodes already proposed has been established.…”

Electrochemical Ultrasensitive Sensing of Uric Acid on Non-Enzymatic Porous Cobalt Oxide Nanosheets-Based Sensor

“…The improved electro-catalytic activity and charge transfer capabilities of metal/metal oxide have attracted considerable interest for their applications in electrode modifications [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Among different metal oxides, cobalt oxide nanomaterials have been utilized to fabricate enzymatic/non-enzymatic sensors where the use of cobalt oxide nanostructures enhances the desired electrochemical properties [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”