It depends on the filter medium used. For standard Method 5 glass or quartz fiber filters, it is best to collect as much material as possible, since we will attempt to remove the particles from the filter for analysis. But if you cannot collect a “cake,” or can use polycarbonate filters (very much the best choice in most circumstances) in place of the glass or quartz fiber filters, particulate catches of less than one milligram (1mg) can be used for particle size determination.
