Characterization of the Vitrocell® 24/48 aerosol exposure system for its use in exposures to liquid aerosols

Background. The Vitrocell (R) 24/48 is an advanced aerosol exposure system that has been widely used and characterized for exposure studies of cigarette smoke, but not for exposure to liquid aerosols with a low gas vapor phase content such as the ones generated by electronic cigarettes. An experimental system characterization for this specific application was therefore performed. Methods: Glycerol model aerosols of different particle size distributions, produced by a condensation mono disperse aerosol generator, were used for exposing small volumes of phosphate-buffered saline in the Vitrocell (R) 24/48. Disodium fluorescein, added as a tracer in the aerosol, allowed the exact aerosol mass deposition to be quantified fluorometrically. Results: The aerosol mass delivery efficiency within the system showed variations in the range of +/- 25%. Aerosol dilution was not fully reflected in aerosol delivery, the achieved aerosol delivery should therefore be determined experimentally. Quartz crystal microbalances underestimated the deposition of liquid aerosols. Unequal delivery of particles of different sizes was detectable, although this effect is unlikely to be relevant under applied experimental conditions. Conclusions: The Vitrocell (R) 24/48 aerosol exposure system can be used for exposures to liquid aerosols, such as those generated by electronic cigarettes. However, our results indicate that, compared with aerosol studies of cigarettes, a higher variability is to be expected.