Metrohm recommends ion chromatography (IC) as a simple, cost-efficient and accurate alternative to using gas chromatography to determine glycerol content in biodiesel.
The free and total content of glycerol in vegetable oil methyl esters (biodiesel) is vital to the quality of biodiesel.
Free and bonded glycerols (total glycerol) cause problems such as injector deposits and filter clogging.
The US ASTM D 6751 and the European EN 14214 specify a maximum total glycerol content of 2400ppm (0.24 per cent) and 2500ppm (0.25 per cent) respectively.
The maximum free glycerol content is limited to 200ppm (0.02 per cent) in both standards, which stipulate gas chromatographic (GC) analysis.
GC methods encounter coelution problems with biodiesel samples produced from or containing lauric oils such as coconut and palm kernel oil.
IC chromatography is applicable to all types of vegetable oil methyl esters.
Prior to chromatographic separation, free glycerol and bound glycerol are isolated by a straightforward extraction and saponification-extraction technique.
Integrated pulsed amperometric-detection following chromatographic-separation achieves a method detection limit (MDL) of 0.7ppm for free and total glycerol, exceeding ASTM and EN performance specifications.
