Laser ionization ion mobility spectrometric interrogation of acoustically levitated droplets

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Chemical Engineering

Background:

• Acoustically levitated droplets offer wall-less microreactors for high-throughput reaction optimization.
• Scaling up optimized reactions from micro- to macro-volumes requires fast, robust, and sensitive online analysis.
• Existing methods lack the speed and automation needed for real-time monitoring of levitated droplet reactions.

Purpose of the Study:

• To develop and demonstrate a direct coupling method for analyzing acoustically levitated droplets using an ion mobility spectrometer (IMS).
• To enable fast, robust, and automated sampling for high-throughput reaction optimization.
• To investigate the feasibility of using mid-infrared laser-induced sampling and ionization for droplet analysis.

Main Methods:

• Direct coupling of acoustically levitated droplets to a homebuilt ion mobility spectrometer (IMS).
• Mid-infrared laser-induced desorption, transfer to gas phase, and ionization of droplet contents.
• Atmospheric pressure ion optics, based on Wiley and McLaren design, for guiding ions into the IMS drift tube.

Main Results:

• Successful demonstration of direct sampling and analysis of acoustically levitated droplets via IMS.
• Mid-infrared laser efficiently desorbs, transfers, and ionizes analytes from droplets.
• Ion trajectory calculations based on a collisional model align well with experimental results.

Conclusions:

• The developed system provides a fast, robust, and automated method for online analysis of acoustically levitated droplets.
• This approach facilitates high-throughput reaction optimization by enabling real-time monitoring.
• The integration of levitated droplets with IMS opens new avenues for microreactor analysis and process optimization.