Field induced droplet ionization (FIDI): A versatile new method to sample ions directly from solution with unique applications in molecular biology

ANYL 226

J. L. Beauchamp, jlbchamp@caltech.edu, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125
Every new method for sampling intact biological molecules has fueled the expanding application of mass spectrometry to molecular biology. Recently developed, field induced droplet ionization (FIDI) holds promise for a broad spectrum of novel applications. The method is deceptively simple. Neutral droplets in a strong electric field are stretched until they develop dual Taylor cones, emitting streams of positively and negatively charged submicron droplets in opposite directions. FIDI sources readily interface with quadrupole, ion trap, orthogonal sampling TOF, FT-ICR, and IMS-MS instruments. A single sampling from a single droplet provides adequate signal for analysis. The droplet can be transported in air, levitated in an acoustic or electrodynamic balance, or suspended at the end of a small capillary. Applications of FIDI to the analysis of biological molecules will be summarized, emphasizing unique studies such as the reactions of ozone with peptides and proteins at the gas-liquid interface of a suspended droplet.