4. Conclusions
An IC system with sample matrix elimination function was used to directly measure phosphate content in biodiesel feedstock. Several J. curcas raw oils were used as the sample oils, and suitable method of sample preparation and IC quantification was developed. The IC method yielded good linearity and detection limits, and reasonable reproducibility. The phosphate and total P contents of 10 raw J. curcas oils were determined. The results showed that the contents varied considerably, and the distribution of inorganic and organic P was diverse.
The accuracy and reproducibility of the IC method could be further improved, and it was observed that various impurities in the oils can interfere with phosphate measurement by peak co-elution. Further study and adjustment of the eluent profile might be necessary to obtain better resolved chromatogram and more accurate results for certain oils. However, it would be case specific, and in general this study provides a practical, economical, reliable and less labor-intensive method for direct determination of phosphate in J. curcas oil. It could also serve as a quick check of total phosphorous and its speciation in various biodiesel feedstock and products, particularly for industrial application.