Analysis of Free and Total Glycerol in Biodiesel Using an Electrochemical Assay Based on a Two‐Enzyme Oxygen‐Electrode System

In this work, an electroenzymatic methodology based on two coupled enzymatic activities (glycerokinase and glycerol‐3‐phosphate oxidase) was developed using an oxygen Clark‐type electrode for the determination of free and total glycerol in biodiesel samples. The enzymatic conversion of glycerol consumes oxygen, which is measured amperometrically in a Clark‐type electrode and correlated with the concentration of glycerol in the sample. The electroenzymatic method proposed showed a good linear correlation coefficient (R=0.9990) with a linear response in the concentration range of 6.25×10^?5 to 6.25×10^?4% (w/v) and limits of detection and quantification at 1.0×10^?5% and 3.0×10^?5% (w/v), respectively. Good correlations were found between the results obtained in this work and those by the gas chromatography technique (R=0.9994). The proposed method was shown to be promising for the analysis of glycerol in biodiesel samples, with a simple and inexpensive methodology compared with the gas chromatography technique.