Bad metals in biodiesel

Four metals which are no good for biodiesel can be measured simultaneously by a novel atomic emission spectroscopic technique using a tungsten coil.. The novel procedure was devised by scientists in the USA and Brazil and is described in Analytica Chimica Acta.

Residual sodium and potassium are usually found in biodiesel because their hydroxides are used in the transesterification process. However, they contribute to the build up of ash in the engine to cause corrosion. Vanadium and chromium increase the levels of pollutants during biodiesel combustion. The new method used a tungsten coil removed from a microscope light bulb to break down the complex biodiesel matrix before atomising the elements for analysis.

The huge advantage of the method is that no sample preparation is required apart from dilution of the fuel with methanol or ethanol. With a heating cycle of 150 s, the detection limits of all four metals were below 100 µg/kg and the tungsten coils last for up to 50 runs, giving a fast and cheap method.