Process and apparatus for quantifying solid residue on a substrate

An apparatus comprising:

• a) an enclosure,
• b) an aerosolizing device comprising a lumen extended from an inlet at one end to an outlet at another end, wherein the lumen is in fluid communication with the enclosure, and wherein the lumen allows an aerosol stream comprising gas and solid material to flow through the aerosolizing device and to exit the outlet of the aerosolizing device,
• c) a port on the enclosure for adding solid material to the aerosolizing device, and
• d) at least one solid substrate located in the enclosure,
• wherein the aerosolizing device further comprises:
• a particle dispersion unit for reducing agglomerates and/or aggregates to solid particles wherein at least 1% of the mass concentration of solid particles have a mass median aerodynamic particle diameter up to about 10 μm,
• wherein said at least one solid substrate is located inside the enclosure and positioned to avoid direct contact with the aerosol stream exiting the outlet of the aerosolizing device.