Nature of some insoluble materials recovered from biodiesel samples.

This paper summarises the work carried out over the last few years on the identification of the insoluble material that may affect quality and performance of biodiesel. The correct isolation and purification procedure is important for sediment identification. The main objective is FTIR analysis of the purified materials. In the present report the FTIR technique was used to provide some preliminary information about the nature of the isolated solid product. In every case, starting from this information, several other tests (carried out by TLC, GC, GC/MS and HPLC) were used to identify the real structure of contaminants. Interesting case studies, such as the recovery and identification of waxes, lysophosphatides, filter aids, citric acid salts, steryl glucosides and other contaminating molecules are presented and discussed. For each case, the logical path for the solution of problem is presented, starting from the purification step, through the FTIR spectrum until specific chemical tests.