AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Electrospray Aerosol Generator with Integrated Soft X-Ray Neutralizer and Usability Enhancements
SHERRIE ELZEY, Jacob Scheckman, Aaron Avenido, Tim Johnson, TSI Incorporated
Abstract Number: 601 Working Group: Instrumentation and Methods
Abstract Electrospray is a common and useful technique for aerosolization of suspended particles and generation of small particles from solutions of dissolved solutes. Electrospray offers significant advantages as a particle generator for aerosol measurements, such as Scanning Mobility Particle Sizer (SMPS) particle size analysis, because it produces stable and small liquid droplets (~150 nm). This method is regularly used to generate particles as small as 2 nm to greater than 200 nm. These particles can then be analyzed in applications including basic aerosol research, protein sizing, manufactured nanoparticle sizing, and others.
The droplets formed by electrospray are highly charged and decrease in size as they dry. The surface charge on the droplet increases and the repulsive force can cause the droplets to fragment. The remaining small particles are highly mobile and strongly repel each other. To combat droplet disintegration and particle losses, electrosprayed droplets can be neutralized using radioactive sources such as Po-210 (Kaufman et al., 1993).
Low-energy soft X-ray neutralizers have been used as an alternative to radioactive sources (Shimada et al., 2002; Lee et al., 2005). Like radioactive neutralizers, soft X-ray neutralizers are able to bring particles to a stable bipolar charge distribution. This has recently been characterized for use in SMPS analysis (Knobel et al., 2013).
Here, we present a new Electrospray Aerosol Generator (EAG) with an integrated soft X-ray neutralizer. During verification of this new device, the size of the generated droplets was characterized and the stability of particle output was evaluated. The EAG was then used to aerosolize PSL of various sizes, as well as metal oxide nanoparticles, for further size distribution analysis with an SMPS. The EAG presented here has also been enhanced to improve usability. A primary mode of status feedback in an electrospray is visualization of the Taylor cone generated by balancing flows and voltages. In most cases, a small viewing window is used to magnify the capillary tip. Instead of a viewing window, a digital camera is used to produce the image of the electrospray at the capillary tip, and the live video image is displayed on the instrument’s touch panel.
Additionally, a particularly short capillary is used, minimizing surface area for particle adhesion and reducing the occurrence of capillary clogging. Further, the capillary mount is designed for easy replacement and also allows for easy connection to an autosampler for automated sample analysis.