Dynamic Behavior of Semivolatile Organic Compounds in Indoor Air. 1. Nicotine in a Stainless Steel Chamber
The dynamic behavior of gaseous nicotine was studied in a 20-m3 stainless steel chamber. Nicotine (10−40 mg) was emitted into the sealed chamber by cigarette combustion or flash evaporation of pure liquid. After 3 h, during which time the airborne concentration was monitored, the chamber was ventilated for 2 h and then resealed to investigate re-emission of sorbed nicotine. Gas-phase, airborne particle-phase, and wall-sorbed nicotine were measured to achieve mass balance closure. More than 80% of the nicotine in the chamber was accounted for by thermally desorbing and collecting sorbed-phase nicotine. More than 99% of the measured nicotine was sorbed to chamber surfaces at equilibrium at 25 °C. The gas-phase data were interpreted using reversible sorption models. A model based on linear partitioning between the gas and sorbed phases could not be accurately fit to the time-dependent data, so equilibrium partitioning was measured separately to test the linear model assumption. The equilibrium data are well described by a nonlinear Freundlich isotherm. Incorporating isotherm parameters into a kinetic, reversible sorption model that assumes a nonlinear, power law rate of sorbed nicotine re-emission and gas-phase deposition provided a significantly better fit to the dynamic data, especially during re-emission after chamber ventilation.