ICP methods are widely used in the analysis of trace elements in oils and animal fats. Current test methods released by ASTM are based on the elemental analysis of oils diluted in organic solvents such as kerosene, xylene or Premisolv. This methodology works well for edible oil analysis. However, for biofuel feedstocks coming from a wide range of sources containing wide ranges of contaminants, we found this method in need of improvement. Working in the food and pharmaceutical industry and being familiar with USP < 233 > and Ph. Eur 5.20 regulations for elemental impurities and references of the monographs to closed-vessel digestion to ensure appropriate digestion conditions, we have decided to transfer oil samples into a measurable aqueous form using CEM microwave digester Mars 6. Performing closed-vessel digestion, we have developed a robust aqueous method for elemental analysis of oils and fats at our laboratory. Our confidence in this methodology has been proved by round robin testing with external labs, recovery of reference oils obtained from external resources, and the results of digested oils that are in good agreement with the results of AOCS LPP challenges. We propose to consider the possibility of including the method of microwave digestion in closed vessels plus aqueous ICP analysis into the AOCS catalog of methods for the analysis of metals in oils and fats.
