Assessment of Single-Photon Ionization Mass Spectrometry for Online Monitoring of in Vitro Aerosol Exposure Experiments

Abstract

Chemical and physical characterization of transported evolving aerosols in an in vitro system is complex. The challenges include appropriate sampling sensitivity, measurement capabilities, and performing online measurements of constituents in the flowing aerosol during exposure. We assessed the performance of single-photon ionization mass spectrometry in measuring aerosol properties within an in vitro aerosol exposure system. The sampling efficiency of the instrument was studied under three protocols to capture the evolving aerosol process inside the exposure system, and it was evaluated using computational fluid dynamics modeling. The changes in the aerosol as dilution is applied show not only a reduction in concentration of the traced substances but also selective sampling due to evolution of the aerosol and (gas/liquid) phase partitioning of the substances forming the aerosol or a change in the aerosol properties. These effects have potentially a direct impact on the delivered dose, as aerosol deposition is dependent on particle size. Dilution affects the chemical concentration of the substances as well as the interconnected physical properties of the aerosol; therefore, the experimental design of in vitro studies should not only report the dilution flow rates but also details of the applied dilution protocol. This adds a layer of complexity to the design and comparison of studies. We also discuss the potential and limitations of single-photon ionization mass spectrometry as a tool in in vitro monitoring of aerosols.

A Direct Probe of the Hydrogen Bond Network in Aqueous Glycerol Aerosols

“…Previously, the thermodynamics and kinetics of water uptake on glycerol aerosols 8 , liquid marbles, 22 and droplets [23][24] have been studies by probing the evaporation and condensation of water vapor onto dried glycerol systems. To date, while there have been studies of aerosolized propylene glycol, glycerol, nicotine, and water by single-photon ionization mass spectrometry, 25 and laser trapping-Raman scattering, 26 we have not seen a report of an X-ray spectroscopic study of aerosolized glycerol water solutions. The closest equivalent to our experimental work is a vacuum ultraviolet photoionization study of a 500 nm glycerol aerosol (without water) between 10.0 and 13.9 eV where nano-focusing, and shadowing was observed in the photoemission processes.…”

State-of-the-art methods and devices for generation, exposure, and collection of aerosols from e-vapor products

“…Experimental setup for online characterization by PI-TOFMS of an e-vapor in an exposure system at the ALI. Source: Frege et al 106 …”

“…Experimental setup for online characterization by PI-TOFMS of an e-vapor in an exposure system at the ALI. Source: Frege et al 106 The setup described here uses a programmable dual syringe pump (PDSP; Burghart Messtechnik GmbH, Wedel, Germany) to generate e-vapor from two EVP devices. The e-vapor is distributed to an exposure system at the ALI, the Vitrocell ® 24/48 exposure system (VC24/48, Vitrocell ® Systems GmbH, Waldkirch, Germany).…”

“…134,135 Frege et al investigated the evolving aerosol inside the VITROCELL ® 24/48 exposure system by using online single-photon ionization MS (SPI-MS) to measure in real time three main constituents of a test aerosol (PG, VG, and nicotine). 106 The aerosol was generated from the EVP P4M3 v 1.0 by using a programmable dual-port syringe pump. The concentrations of PG, VG, and nicotine were measured in the aerosol sampled at the end of each delivery line and at the QCM port in three exposure protocols: (i) no dilution, (ii) gradually increasing dilution at each line, and (iii) single-dilution applied only once at the beginning of the line.…”

A Computational and Experimental View of Hydrogen Bonding in Glycerol Water Clusters

“…Glycerol ionization has been invoked in a case of surface ionization of liquid glycerol by sodium ions, 19,20 and also VUV photoionization of glycerol has been undertaken in aerosols. 21,22 We have studied the photoionization of glycerol molecules and its dimer in the gas phase using synchrotron-based vacuum ultraviolet (VUV) photoionization mass spectrometry. 23 Our combined experimental and theoretical study of glycerol water cluster photoionization presented here builds upon this framework and also complements the X-ray, IR, and THz study performed on aqueous glycerol aerosols.…”