Cascade Impactor Technology Leaps Forward with MSP’s latest real-time QCM-MOUDI™ Impactor

Share Article

MSP’s real-time QCM-MOUDI™ Impactor is a leap forward in cascade impactor technology for size-fractionation and mass measurement of aerosols. The new QCM-MOUDI™ has a 25-nanogram mass resolution which is accomplished through humidity control and advanced electronics, while keeping samples available for post-collection analysis.

Real-time QCM-MOUDI Impactor

Real-Time QCM-MOUDI Impactor

Researchers can now accelerate their aerosol studies by measuring aerosol mass in real-time with the breakthrough equipment technology contained in the QCM-MOUDI™ Impactor device from MSP.

Researchers can now accelerate their aerosol studies by measuring aerosol mass in real-time with the breakthrough equipment technology contained in the QCM-MOUDI™ Impactor device from MSP.

Cascade Impactor History background

Cascade impactors have been used for collecting and size-fractionating aerosols for over a century. Significant advances were made in this technology in the late 1970s and early 1980s by MSP founders at the University of Minnesota. In particular, collection of nanometer particles (<100 nm) was enabled, and a uniform deposit feature was introduced (see Kuhlmey et al. 1981 and Marple et al. 1981). These advancements led to the Micro-Orifice Uniform Deposit Impactors(MOUDI™) introduced as commercial products by MSP Corporation. These precision cascade impactors are designed for sampling and collecting size-fractionated particle samples for gravimetric and/or chemical analyses. Several models of the MOUDI™ product line cover flow rates as high as 30 L/min and the lowest cut-sizes as small as 10 nm.

The MOUDI differs from other conventional cascade impactors in the use of a large number of micro-orifice nozzles to reduce jet velocity and pressure drop, minimize particle bounce and re-entrainment, and enhance collection efficiency. As many as 6,000 nozzles with diameters as small as 50 μm are used. Some models also have the uniform-deposit feature achieved by rotating the impaction plate relative to the nozzles so that the particle deposits under the nozzles can be spread out uniformly over the entire impaction area.

MSP research yields the real-time QCM-MOUDI™

This new capability enables researchers to actively monitor aerosol mass measurements, while simultaneously collecting size-fractionated samples for post-collection analysis.

A Quartz Crystal Microbalance (QCM) is a sub-millimeter thick wafer cut out of a single crystal of quartz. Metallic films deposited on both sides of the wafer serve as electrodes that are used to probe the natural frequency of vibration of the QCM. QCMs can be mounted to the impaction surfaces of cascade impactors. The aerosol mass depositing on them results in a drop in the frequency proportional to the deposited mass. QCM surfaces can be cleaned after a measurement session and reused.
Early attempts to utilize QCMs for real-time aerosol mass measurement were hampered by technological problems including the failure of the aerosol to remain attached to the QCM as it vibrated at MHz frequencies. After meticulous investigation of the earlier anomalies in QCM response, MSP has developed a proprietary technology to reliably measure size-fractionated aerosol masses up to 100 micrograms. In particular, humidity conditioning of the sampled aerosol ensures reliable coupling of aerosols to QCMs (patent pending).

For over 30 years MSP has created micro- and nano-particle instrument and equipment technologies for scientific research and industrial applications. MSP is known world-wide for particle technology expertise in helping researchers and manufacturers solve tough problems with creative equipment designs. Contact MSP at sales(at)mspcorp(dot)com to discuss micro- and nano-particle application or research needs.

Share article on social media or email:

View article via:

Pdf Print

Contact Author

Daryl Roberts
Follow us on
Visit website