Free and total glycerin in biodiesel and biodiesel mixtures in accordance with ASTM D7591

Biodiesel or green diesel is manufactured from fats and vegetable oils through ester interchange of the triglycerides they contain, during which glycerin accumulates as byproducts in both free and bonded forms. These accelerate fuel ageing and lead to deposits and clogged filters, which is why maximum permissible highest concentrations have been established (in the US in ASTM D6751 and in the EU in EN 14214).

The two specifications prescribe the ion chromatography determination of free and bonded glycerin. This Note describes the determination with the aid of the Metrosep Carb 2 - 150/4.0 column in accordance with ASTM D7591.