Electrochemical detection of tryptophan in pineapple fruit using a green and chemically synthesized PANI/CuO nanocomposite modified electrode

Abstract

This study investigated the electrochemical detection of Tryptophan (Trp) in pineapple using a glassy carbon electrode (GCE) modified with nanocomposites of green and chemically synthesized copper oxide-polyaniline (PANI/CuOgrn and PANI/CuOchm). Given the properties of PANI/CuOgrn and PANI/CuOchm that have never been applied in the detection of Trp, it indicates that the development of a highly sensitive and selective sensing platform for Trp-is necessary. Such a platform would take advantage of high electric conductivity, larger surface area, and improved catalytic activity of the nanocomposites. PANI/CuOgrn and PANI/CuOchm nanocomposites were formed by doping polyaniline (PANI) with green and chemically synthesized copper oxide (CuO) nanoparticles. Using Debye-Scherrer the particle sizes of PANI/CuOgrn and PANI/CuOchm were found to be 15 nm and 13 nm, respectively. Through cyclic voltammetry (CV) and square wave voltammetry (SWV), the electrochemical behaviour of CuOch, CuOgrn, PANI/CuOchm, and PANI/CuOgrn electrodes was studied, with the focus on comparing the nanocomposites for tryptophan (Trp) catalysis. GCE-PANI/CuOchm showed a higher current response of 3.2 μA than GCE-PANI/CuOgrn. SWV was used to determine Trp, with the linear range of 5.11 μM to 25.85 μM and limit of detection (LOD) values of 3.947 and 2.037 μM for GCE-PANI/CuOchm, and 3.434 and 2.427 μM for GCE-PANI/CuOgrn. The GCE-PANI/CuOchm electrode achieved a recovered percentage of 96 % to 109 %, with an average RSD value of 18.3 (n=3), while the GCE-PANI/CuOchm electrode achieved a percentage recovery of 85 % to 103 % with an RSD value of 12.7 (n=3). The high recovery percentages for both electrodes confirm their dependability in detecting Trp. The high concentration of Trp-in the fruit and the electrode's sensitivity to identifying Trp-in actual sample analysis may account for the high recovery percentage observed.