Desorption Electrospray Ionization: Achieving Rapid Sampling Rates

The sampling rate and imaging capabilities of desorption electrospray ionization (DESI) are examined using a rotating sample platform combined with Hadamard transform time-of-flight mass spectrometry (HTTOFMS), a multiplexed time-of-flight technique that allows for millisecond acquisition of full mass-to-charge ratio scans. DESI-compatible dyes are used to produce spatially defined sample patterns on poly(methyl methacrylate) discs. Control of disk rotation rate sets the residence time of the sample spots in the DESI plume, and thus the sampling rate. Surface patterns of alternating analytes are spectrally resolved up to 80 samples/s and single-analyte spots up to 50 samples/s. The rapid movement of the surface under the DESI plume allows for high DESI solution flow rates without blurring the chemical information on the surface. Data from multiple rotations can be additively combined, generating a chemical image of the surface with improved signal-to-noise characteristics. This multipass data enables anal...