Determination of free glycerol in biodiesel at a platinum oxide surface using potential cycling technique

Abstract

A novel, inexpensive and fast method based on the electrooxidation of glycerol on platinum electrodes by the potential cycling technique has been designed for the determination of free glycerol in biodiesel. A wide range of linearity was achieved between 15 and 150 mg L(-1) (0.16 and 1.6 mmol L(-1)), which corresponds to concentrations ranging between 56 and 560 mg kg(-1) (glycerol:biodiesel) for an extraction using 2g biodiesel. A method for the fast extraction of glycerol from biodiesel with water followed by elimination of organic interferents has also been developed, so that the novel determination method can be applied to various biodiesel samples. The excellent repeatability allows determination of glycerol in numerous samples, with no need for recalibration.

Analytical chemistry in Brazil: healthy and growing

“…The electrooxidation of the analyte on platinum electrodes was proposed for determination of free glycerol in biodiesel by the potential cycling technique. 165 The analyte was determined after extraction with water and the procedure presented linear response within 15 and 150 mg L -1 . In other approach, the raw materials used to produce biodiesel were identified by mass spectrometry with selective ion monitoring coupled to gas chromatography.…”

Electrochemical Methods in Analysis of Biofuels

“…The first one is the work by Lourenço and Stradiotto [125] which have used a Pt electrode to quantify free glycerol in biodiesel samples. The analytical method is based on electrocatalytic oxidation of glycerol promoted by PtO x electrogenerated onto electrode surface.…”

Uso de eletrodos de cobre e eletrodos modificados como sensores eletroquímicos

“…Para esta reação é necessária a utilização de etanol anidro, pois a presença de água leva à formação de emulsões [49]. A conversão completa dos triacilglicerois em ésteres envolve três passos consecutivos, sendo o biodiesel e o glicerol (1,2,3-propanotriol) os produtos desta reação [49,54], conforme visto na Figura 1.1.…”

“…A corrente que surge no intervalo entre −0,50 e −0,15 V é de natureza capacitiva, correspondendo à dupla camada elétrica. Portanto, nessa região a superfície do eletrodo de Pt encontra-se livre de hidrogênio e oxigênio adsorvidos [54,[180][181]. Em potenciais mais positivos que −0,15 V, o pico III a corresponde aos processos de oxidação da superfície da Pt, com consequente formação de óxidos [180][181][182].…”

“…A não sobreposição total das curvas de oxidação é provavelmente devido à limitação na adsorção do glicerol na superfície da Pt durante a varredura negativa de potencial [54,181], em que se observa o início da redução dos óxidos de Pt (pico IX c ).…”