Electrochemical Analysis of Free Glycerol in Biodiesel Using Reduced Graphene Oxide and Gold/Palladium Core-Shell Nanoparticles Modified Glassy Carbon Electrode

Victor Magno Paiva,Carlos Alberto Achete,Daniela Ramos Ferreira,Eliane D'Elia,Braulio Soares Archanjo,Carlos Alberto Senna,Kelly Leite Dos Santos Castro Assis,Emerson Schwingel Ribeiro

doi:10.3390/pr9081389

Abstract

Glycerol is a major byproduct obtained in the production of biodiesel, an important renewable fuel. The presence of free glycerol in fuel can have structural and performance consequences with respect to the engine, making fuel quality control important. The standard method to analyze glycerol in biodiesel is gas chromatography, a time-consuming and expensive technique. In this context, an electrode based on glassy carbon electrodes (GCEs) modified with reduced graphene oxide and core-shell gold@palladium nanoparticles was developed for the determination of glycerol in biodiesel. The free glycerol analysis was performed in the aqueous phase obtained by liquid–liquid extraction from a biodiesel sample. Cyclic voltammetry was chosen as the method for glycerol electrochemical analysis to regenerate active sites and promote greater sensor stability. The modified Au@Pd/rGO/GCE electrode showed an excellent performance, obtaining a linear range of 18.2 to 109 µmol L−1 with a correlation coefficient of 0.9895, limits of detection and quantification of 5.33 and 17.6 µmol L−1, respectively, high stability during 1000 cycles, and recovery values of 86% and 87% in the quantification of glycerol in biodiesel samples. The proposed method proved to be a great alternative for the analysis of glycerol in biodiesel, being a fast, sensitive, and low-cost technique due to its high stability and the use of small quantities of reagents.

Highlights

It is important to note that glycerol is obtained as a co-product in biodiesel production, an important alternative fuel that reduces dependence on oil and meets the green demand to avoid polluting the environment
After the electrochemical reduction of the GO, the electroactive area of the electrode increased by 4.5 times and the k0 approximately 3 times
Using the Randles–Sevcik [28,29,30] equation (Equation (1) it was possible to calculate the electroactive area of the electrodes, showing that after glassy carbon electrodes (GCEs) modification the electroactive surface area (ECSA) increased 64% (ECSA of GCE = 0.042 cm2, ECSA of reduced graphene oxide (rGO)/GCE = 0.069 cm2 )

Summary

Introduction

Glycerol is a very important non-toxic substance that is often used in various industries, including those of cosmetics, foods, pharmaceuticals, and personal care products. It has recently been used as an alternative energy source through the oxidation of alcohol in fuel cells [1,2,3,4]. It is important to note that glycerol is obtained as a co-product in biodiesel production, an important alternative fuel that reduces dependence on oil and meets the green demand to avoid polluting the environment For this reason, the use and study of biodiesel have increased greatly in recent years [5]

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