Analysis of Total Sulfur in Biodiesel / FAME samples

In the past few years, the market has seen an increase in complex matrices in a wide spectrum of different fuels. Sulfur is a critical component and legislation push for lower sulfur concentrations in fuels, mainly to protect our environment and monitor degradation in catalytic processes.

In efforts to minimize impacts on human and environmental health, biodiesels and mixtures of biofuels with fossil fuels are becoming increasingly popular. Due to the wide variety of biofuels like vegetable oils, cooking oils, animal fats and other renewable oils, also the quality and composition have a wide variety, which in terms impacts the combustion characteristics.

During the production process of these biofuels, the triglyceride molecules are converted (called transesterification) to matrices like fatty acid methyl esters (FAME) in biodiesel (a-polar phase) and glycerol (polar phase), which have to be separated. Furthermore, the biodiesel phase has to be washed to eliminate remaining inorganic pollutants. All in all these processes are complex and the composition of the sample matrix is very diverse and very relevant for the method to choose for the analysis of Total Sulfur in the biodiesel/FAME sample.

Total Sulfur in such samples can be measured by using combustion followed by the UV-fluorescence detector technique, as defined in the methods ISO 20846 and ASTM D5453. The challenge for the test laboratories is to choose between the two different methods of sample introduction: the direct injection or boat inlet. Where direct injection has the advantage of speed but the boat inlet can be more analytically correct.

The majority of biodiesel/FAME samples have similar matrix composition and boiling point ranges as common diesel fuels. For these samples, fast analysis by direct liquids injection into a pre-zone/heated furnace in a few minutes is applicable. The difficulty arises when the matrix composition differs because of the presence of higher boiling point components, salts from the washing process, remaining glycerol or other unforeseen contaminating components. This requires a more defensive, controlled sample introduction method by injecting the sample in a sample boat, which enters the furnace gradually allowing all components to combust completely.

Trace Elemental Instruments (TE) offers comprehensive solutions for all of the above matrices.

The Xplorer-TS analyzer is the benchmark in the industry for unattended analysis of Total Sulfur. It offers accurate results for biodiesel/FAME samples with the ability to choose between fast analysis and fully controlled analysis of complex matrices without contaminating the instrument. Furthermore, the Xplorer-V NS Vertical instrument enables the analysis of an even wider scope of sample matrices due to a new furnace design and sample injection technology.

Please contact sales@teinstruments.com for advice about the best configuration for your samples or send us an application request for your specific sample matrix. TE Instruments is interested to run your samples on our full range of instruments in one of our application laboratories in Delft (NL) or Houston (USA). Let the data speak for itself!