Biodiesel is usually an effective blending component for petroleum-based diesel fuel. However, biodiesel-mixed diesel fuel can be a problem in engines designed for only petroleum-based diesel. Also, blended biodiesel can promote biological growth and increase instability of the diesel fuel resulting from the buildup of oxidation products. Thus, biodiesel-blended diesel fuel can cause issues in stationary standby diesel engines, such as those used in nuclear plants. The ASTM D7806-12 test method was developed for the determination of biodiesel (FAME) content in diesel fuel oils in the concentration range from 1 to 30% by volume. In this application note, we demonstrate the applicability of any of the three Agilent FTIR spectrometers (4500, 5500, and Cary 630) to this method. The Agilent systems can be used for:

• Quality control in the production and distribution of diesel fuel and biodiesel blends containing FAME

• Routine checks of incoming blended diesel fuels from a distributor

The Agilent FTIR spectrometers demonstrated excellent repeatability (X ± 0.02%), better than X ± 0.3% as defined in the ASTM D7806-12 method, where X is the biodiesel concentration. Whether the biodiesel content of a blended fuel needs to be tested in the lab or in the field, the three Agilent spectrometers provide an easy, accurate, and portable means for measurement. This gives analysts the flexibility to choose the best instrument based on their routine analysis requirements.