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

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.

Fingerprinting of propolis by easy ambient sonic-spray ionization mass spectrometry

“…EASI, which was originally termed DeSSI [32], is one of the simplest, gentlest and most easily implemented ionization methods. EASI uses super-sonic-spray ionization to create minute droplets which become charged due to statistical imbalance distribution of charge (cations and anions).…”

“…EASI displays, therefore, several unique features: requires no voltage to eliminate counter-ions, no voltage switches from positive to negative ion modes and vice-versa, no heating for desolvation and is less prone to analyte oxidation. Comparisons of EASI and DESI for the same sample [32] showed that there were less background cluster ions from solvent ionization (noise) and in some cases higher abundance of the analyte ions in the spectrum, when EASI was used. Otherwise the EASI-MS data are quite similar to ESI-MS or SSI-MS data.…”

“…EASI has already been applied with success to different analytes and matrixes such as biodiesel [33] and drug tablets [32]. It has also been coupled to membrane interface mass spectrometry-MIMS [31] and thin layer chromatography-TLC [33] among others.…”

Direct profiling of phytochemicals in tulip tissues and in vivo monitoring of the change of carbohydrate content in tulip bulbs by probe electrospray ionization mass spectrometry

“…In DESI, high-speed electrically charged drop-lets directly sprayed onto the sample surface and secondary ions would be generated during the process of surface collisions [5][6][7]. A similar technique related to DESI, where the solution was sprayed with very highspeed nebulization auxiliary gas but no voltage applied, is called desorption sonic spray ionization (DeSSI) [8] or easy ambient sonic-spray ionization (EASI) [9]. There are several other two-step techniques of coupling laser desorption and ESI.…”

Detection of trace levels of lead in aqueous liquids using extractive electrospray ionization tandem mass spectrometry

“…Recently, breakthrough of mass [36,37]. After DESI, more than 20 ambient ionization techniques were further developed, including direct analysis in real time (DART) [38,39], surface desorption atmospheric pressure chemical ionization (DAPCI) [40,41], extractive electrospray ionization (EESI) [42], low temperature plasma (LTP) [43,44], and easy ambient sonic ionization (EASI) [45]. Two major advantages of ambient mass spectrometry are minimal sample pre-treatment and high-throughput MS analysis [46][47][48].…”