Desorption sonic spray ionization for (high) voltage‐free ambient mass spectrometry

TLDR

DeSSI uses neither heating nor high voltages, offering a more benign environment for ambient mass spectrometry compared with DESI. DeSSI generates a supersonic spray of charged droplets that desorbs and ionizes drug molecules from tablet surfaces at ambient conditions, matching DESI sensitivity while producing cleaner spectra, enabling MS/MS, and improving sampling homogeneity and ion signal longevity.

Abstract

Sonic spray ionization is shown to create a supersonic cloud of charged droplets able to promote efficient desorption and ionization of drugs directly from the surfaces of commercial drug tablets at ambient conditions. Compared with desorption electrospray ionization (DESI), desorption sonic spray ionization (DeSSI) is advantageous since it uses neither heating nor high voltages at the spray capillary. DeSSI therefore provides a more friendly environment in which to perform ambient mass spectrometry (MS). DeSSI-MS is herein evaluated for the analysis of drug tablets, and found to be, in general, as sensitive as DESI-MS. The (high) voltage-free DeSSI method provides, however, cleaner mass spectra with less abundant solvent cluster ions and with enough abundant analyte signal for tandem mass spectrometry (MS/MS). These features may therefore facilitate the DeSSI-MS detection of low molar mass components or impurities, or both. The higher-velocity supersonic DeSSI spray also facilitates matrix penetration thus providing more homogenous sampling and longer lasting ion signals.