Uptake of Semivolatile Vapors to Cyclodextrin Particles

Cyclodextrins are used to sorb noxious vapors as the active agent in air-cleaning products. Here, we explore the capacity of α-cyclodextrin to absorb molecules representing odorants. The semivolatile sugar erythritol (C4H10O4) is soluble in α-cyclodextrin. It evaporates from pure seed particles in an aerosol suspension in roughly 3 h at room temperature and more slowly when mixed with α-cyclodextrin, consistent with an ideal solution (Raoult’s law). However, when erythritol evaporates from particles in the presence of other particles containing α-cyclodextrin at low relative humidity, the erythritol does not appear to be taken up into the α-cyclodextrin (unlike other sugars such as glucose, sucrose, and raffinose). This suggests that the dry α-cyclodextrin is sufficiently glassy to resist the uptake of the semivolatile polyol. In contrast, α-cyclodextrin will sorb the much more volatile sesquiterpene β-caryophyllene, showing evidence for a substantially low (favorable) activity coefficient toward this species, illustrating the capacity of α-cyclodextrin to capture and retain highly volatile compounds.