Method for Improving Spatial Resolution of Liquid-assisted Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry

Abstract Liquid-assisted surface desorption atmospheric pressure chemical ionization source (LA-DAPCI) technique shows good potential in complex matrix mass spectrometry imaging. Due to primary ions and high density charged droplets of solvent generated by corona discharge, analytes on sample surface are extracted and ionized efficiently. However, direct application of the DAPCI ionization for mass spectrometry imaging of complex matrix analytes usually tends to be challenging because of low spatial resolution. To resolve this problem, several ion source parameters and experiment conditions were optimized in the present work, including ion source configuration, chemical composition of the extraction solvent, geometry parameters, solvent flow rate and pressure of nebulizing gas. The results presented here confirmed that the spatial resolution of LA-DAPCI was improved (from (441 ± 14) μm to (58 ± 7) μm). The proposed LA-DAPCI-MS/MS method was successfully used to profile the distribution of Rhodamine 6G with a limit of detection of 0.01 ng cm −2