Method for Determination of Ice Nucleating Particle (INP) Concentration


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Thomas C J Hill
Paul J DeMott
Sonia M Kreidenweis
Anthony J Prenni
Sam A Atwood

At A Glance

By leveraging the cleanliness and low cost of molecular biology’s plastic consumables, CSU researchers have developed a more cost-effective instrument and method to count ice nucleating particles utilizing freezing point depression.  The technology has a variety of applications including measurement of atmospheric aerosols and cloud seeding agents.


Reference No.: 15-004

Technology Overview

Researchers at Colorado State University have developed a cost-effective instrument and method that counts INPs (ice nucleating particles) from multiple and diverse samples simultaneously, with large dynamic range, and at very low concentrations. At temperatures warmer than about -36°C, aerosol particles known as ice nucleating particles (INP) are necessary to trigger the first formation of ice crystals in clouds (termed heterogeneous nucleation). Ice nucleation in the atmosphere is required to form precipitation.

This technology is able to detect low concentrations of INP, process large volumes of liquid, simultaneously analyze a large number of diverse samples, and obtain spectra over a wide range of supercooling (down to -26°C).

The advantages of this technology are principally derived from the use of components normally used for analyses in molecular biology, which allows the technology to take advantage of the cleanliness and cheapness of the field’s plastic consumables. An additional robust cooling mechanism and other features allow the technology to greatly reduce contamination from background INP, thereby increasing accuracy and lowering the detection limit.

Current on-line instrumentation is generally very expensive, heavy and requires large amounts of power (making accommodation on an aircraft problematic). Furthermore, they require modification to capture the INPs detected for additional analyses. In contrast, this technology is cost-effective and allows samples to be collected anywhere on any extractable medium and stored frozen for later analyses (by either this technique or others, such as chemical identification or DNA analyses).

Recently verified against the current state-of-the-art real-time INP detectors, this technology is ready for wide spread utilization and is suitable for analysis of atmospheric aerosols (re-suspended from filters or concentrated in water by an impinger), precipitation, seawater, soil (in suspensions), dust and microbes on plant surfaces (in leaf washings), and pure cultures of ice nucleating organisms (e.g., ice nucleation active bacteria and fungi, Snomax, cloud seeding agents).

Note that this technology can be used to conveniently characterize commercial cloud seeding agents that can be dispersed into aqueous solution. In this application, it has the added benefit of not exhausting potentially hazardous materials into the atmosphere, as would a flow-through method in which the seeding agents are suspended in air.


  • High performance: low detection limit, large temperature range (down to -26°C), parallel analysis of multiple samples.
  • Convenient: low cost, applicable to diverse set of samples, samples available for subsequent analyses.
  • Accurate: verified against current real-time INP detectors.
  • Ready for use with atmospheric aerosols, precipitation, soil, microbes, cloud seeding agents, and more

Last updated: May 2020