The regulated level of diesel particulate mass for 2008 light-duty diesel on-road engines will be 0.005 g km−1 in Europe. Measurements by weighing and analysis of this low level of particulate mass based on chemical extraction are costly, time consuming and hazardous because of the use of organic solvents, potentially carcinogenic. An alternative to this analysis is proposed here: a thermal mass analyser that measures the volatile fraction (VOF) as well as the soot fraction of the particulate matter (PM) collected on a cleaned fibre glass filter. This paper evaluates this new thermal mass measurement (TGA) as a possible alternative to the conventional chemical extraction method, and presents the results obtained with both methods when testing a diesel engine fuelled with a reference diesel fuel (REF), a pure biodiesel fuel (B100) and two blends with 30% and 70% v/v biodiesel (B30 and B70, respectively).