PM sample preparation
DGI
-20
Wood smoke particles were collected onto PTFE substrates from the chamber with a 5-stage (> 2.5 µm to < 0.2 µm) gravimetric impactor (DGI, Dekati Ltd., Finland). Particle collecting and blank control filters were eluted in high pressure liquid chromatography grade methanol under sonication, twice for 30 min at 22 °C (room temperature). PM suspensions were pooled, and excess methanol was evaporated using a rotary evaporator at 30 °C under vacuum. The concentrated PM sample was then aliquoted, calculated on a mass basis, dried in glass tubes under nitrogen flow and stored at -20 °C.