Needle-Trap Device Containing a Filter: A Novel Device for Aerosol Studies

Particles in an aerosol sample contain a portion of the total available analytes. Therefore, particle trapping is required to fully characterize a gaseous sample. Needle-trap devices (NTDs) are highly useful to this end, as they allow sampling and preconcentration of free analytes, as well as the trapping of particles. Packing sorbents into the needle creates a filter that traps solid particles or liquid droplets. However, the particle-trapping efficiency of sorbent-packed NTDs is limited, especially for nanoparticles. To address this issue, an aerogel based on electrospun polyacrylonitrile (PAN) was prepared for trapping small particles to analyze particle-bound analytes. The PAN aerogel filter was fabricated by cutting electrospun PAN fibers and removing the remaining solvent via freeze-drying to obtain a light porous fibrous structure. The PAN aerogel was heated (H-PAN) prior to packing to ensure stability during thermal desorption. The trapping efficiency of the H-PAN-packed NTD was measured using a range of conditions, with high filtration efficiencies (>99%) being obtained in all cases. The mechanical stability of the H-PAN aerogel was tested using multiple extraction/desorption cycles with and without solid sorbent particles, with results indicating high repeatability (n = 94, relative standard deviation (RSD) <6%). The developed NTD was compared to thin-film microextraction with respect to their ability to characterize breath samples obtained with or without face masks; the NTD was able to trap both free and droplet-bound analytes, while thin-film microextraction was only able to extract free analytes, which is fully reflected in concentrations obtained with these two methods.