Metrohm has recommended ion chromatography (IC) as a cost-effective and accurate alternative to gas chromatography (GC) when determining the glycerol content in biodiesel.
Current US and European standards stipulate GC to determine the glycerol content in biodiesel.
However, this method is both tedious and expensive.
Metrohm recommends IC as a simple, cost-efficient and highly accurate alternative.
The free and total content of glycerol in vegetable oil methyl esters (biodiesel) is of paramount importance for the quality of biodiesel.
Both free and bonded glycerols (=total glycerol) lead to severe operational 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 2,400ppm (0.24 per cent) and 2,500ppm (0.25 per cent), respectively.
The maximum free glycerol content is limited to 200ppm (0.02 per cent) in both standards, which stipulate GC analysis involving time- and reagent-consuming derivitasations.
In addition, GC methods encounter coelution problems with biodiesel samples produced form or containing lauric oils, such as coconut and palm kernel oil.
In contrast to GC, the presented method 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, respectively.
Integrated pulsed amperometric detection following chromatographic separation achieves and outstanding method detection limit (MDL) of 0.7ppm for free and total glycerol and exceeds ASTM and EN performance specifications.