Analysis Method for P, S and Cl in Bio-diesel and Bio-ethanol

Rigaku Corporation (USA) recently announced the publication of a new application note describing the quantitative analysis of trace amounts of controlled elements in different base oils, including bio-diesel and bio-ethanol, by wavelength dispersive X-ray fluorescence (WDXRF) spectrometry.

Rigaku application note XRF 5032 describes quantitative analysis of trace amounts of phosphorus (P), sulphur (S) and chlorine (Cl) in biofuels using the Rigaku Primini Biofuel WDXRF elemental analyser. The report includes complete information regarding sample preparation, method calibration and repeatability.

In addition to increased efficiencies in the use of conventional fossil fuels, environmental concerns have led to greater use of non-fossil fuels such as bio-ethanol and bio-diesel. As with conventional fuels, the levels of phosphorus, sulphur and chlorine in biofuels have been reduced to protect engines and catalysts and prevent air pollution.

In the analysis of biofuels, oxygen levels and carbon/hydrogen ratios affect the analysis results of the target elements. Rigaku has developed a new method to correct for this influence by analysing scattering X-rays from samples.

For the published method, analysis was performed using the Primini Biofuel WDXRF spectrometer, a bench-top analyser optimised for sub-ppm detection limits of P, S and Cl, The report describes the performance of the Primini Biofuel spectrometer using the Lite Matrix Correction method. In Lite Matrix Correction, an additional analysing crystal and detector are added to the spectrometer for measurement of the X-rays. The method requires only standards for elements to be analysed and needs no special standards for correction. By applying the method, accuracy can be significantly improved, even for different oil matrices. Additionally, the same calibration can be used for both bio-diesel and bio-ethanol.

The results demonstrate that the benchtop Primini Biofuel WDXRF spectrometer can give precise determination for trace levels of P, S and Cl in different base oils.