# Ion Chromatography as a Sustainable Alternative for Monitoring Ethanol and Free Glycerol in Biodiesel

## TL;DR

Ion chromatography is shown to be a reliable and eco-friendly method for measuring ethanol and glycerol in biodiesel.

## Contribution

Ion chromatography is proposed as a sustainable alternative for quantifying ethanol and free glycerol in biodiesel.

## Key findings

- Ion chromatography achieved detection limits of 0.1 and 0.94 mg·L–1 for glycerol and ethanol, respectively.
- The method showed high repeatability and reproducibility, meeting AOAC validation standards.
- The technique reduces toxicity, analysis time, and costs by eliminating the need for organic solvents.

## Abstract

The amounts of glycerol and ethanol in purified biodiesel
are standardized
by regulatory agencies to ensure the performance of the biofuel in
combustion. Therefore, the correct measurement of these components
is essential to evaluate the final quality of biodiesel and to monitor
its synthesis. In addition, evaluation of the composition in ethanol
and glycerol is also relevant in modeling the kinetics of the transesterification
reaction. Ion chromatography was evaluated as an alternative technique
to identify and quantify ethanol and free glycerol in biodiesel samples
from heterogeneous, homogeneous, and enzymatic catalysis. The analytical
method exhibited detection limits of 0.1 and 0.94 mg·L–1 and quantification limits of 0.3 and 2.83 mg·L–1 for glycerol and ethanol, respectively. Additionally, the analytical
method demonstrated suitable repeatability (RSDglycerol = 0.14% and RSDethanol = 0.80%), reproducibility (RSDglycerol = 1.27% and RSDethanol = 3.32%), and selectivity,
proving to be reliable in relation to the matrix effects according
to the validation guide of the Association of Official Analytical
Chemists (AOAC). Ion chromatography has been demonstrated to be an
alternative technique that is adequate for the quantification of ethanol
and glycerol in different alkyl ester systems. Moreover, the technique
dispenses the use of organic solvents, resulting in a considerable
reduction of toxicity, analysis time, and analytical costs, and contributes
to both environmental and operational securities.