Ion Chromatographic Determination of Anions and Cations in Biofuels

In order to control the quality of biofuels such as biodiesel and bioethanol, ion chromatography (IC) is the method of choice. It is straightforward, fast and accurate and requires only moderate expenditures on instrumentation.
Biofuel quality can be severely impaired by the presence of ions that
lead to corrosion in the vehicle components and cause salt deposits
clogging filters and fuel injector nozzles.
Therefore, standards defining quality specifications and test methods have been developed. In this context ion chromatography plays a crucial role. Besides the quantitation of cations, glycerol and antioxidants in biodiesel, a direct-injection IC method allows the determination of the chloride and sulfate content in bioethanol according to the recent ASTM D 4806 standard.
Traces of anions in a gasoline/ethanol blend such as E85 can accurately be determined in the subppb range after Metrohm Inline Matrix
Elimination using anion chromatography with conductivity detection after
sequential suppression. While the analyte anions are retained on the preconcentration column, the interfering organic gasoline/bioethanol matrix is eliminated.
Detrimental alkali metals and water-extractable alkaline earth metals in
biodiesel are determined in the sub-ppm range using cation chromatography with direct conductivity detection applying automated extraction with nitric acid and subsequent Metrohm Inline Dialysis.
Unlike high-molecular substances, ions in the high-ionic strength matrix diffuse through a membrane into the low-ionic water acceptor solution.