Biodiesel is seldom used neat (B100), typically being blended with fossil diesel at ratios from 5% v/v (B5) to 30% v/v (B30). Verifying the FAME content of diesel-fuel blends is an important aspect of quality control and auditing of blending and distribution operations. Because FAME has a strong infrared absorption at 1745 cm-1 due to the ester carbonyl group, infrared spectroscopy is an excellent technique for this analysis, and there are EN and ASTM® standard test methods describing the procedure