Problems! Low recovery was observed in the residue fraction after combustion, as indicated by the 125I tracer. This is probably attributed to material of aerosol filter that is Polypropylene Acid Esters. During combustion, the material can’t be decomposed completely and goes into trap solution, which affects following extraction due to forming mixed phase of water and organic solvent that is hard to separate. Although these experiments look easy and straightforward in my research plan I am amazed how often these unexpected problems appear. They can be of any kind and appear any time. Many people around here have hair already gray, I guess these problems are creating it! I have talked about the problems to my supervisor and discussed with the scientists who knows about the air sampler but got no real suggestions. If we can filter the phase away would be ok but I don’t seem to succeed with our current filters.