A dopant for improved sensitivity in easy ambient sonic‐spray ionization mass spectrometry

Abstract

Recently, 3-nitrobenzonitrile (3-NBN) has been used to improve sensitivity of sonic-spray ionization mass spectrometry. Easy ambient sonic-spray ionization (EASI) is one of the simplest, gentlest and most used spray-based desorption/ionization ambient techniques, but limited sensitivity has been commonly taken as its major drawback. Herein we investigate the use of 3-NBN as a dopant in EASI-MS for improved sensitivity. Using a few typical EASI samples as test cases, the presence of 10 ppm (µg ml(-1) ) of 3-NBN in the spray solvent showed two to fourfold gains in EASI-MS sensitivity as measured both by total ion current and S/N ratios, accompanied with significant reductions in chemical noise. Sensitivity for DESI using 3-NBN as a dopant also improved and dopant DESI versus dopant EASI sensitivities were compared. The use of solvent dopants seems therefore to be a promising strategy to improve sensitivity for spray-based ambient MS techniques. Copyright © 2015 John Wiley & Sons, Ltd.

Ion formation in droplet‐assisted ionization

“…To further investigate the role of solvent composition on ionization, an efficient matrix for conventional solid-state MAI, 3-nitrobenzonitrile (3-NBN), [16][17][18] was added to 50:50 water/acetonitrile solution to investigate the possibility of matrix enhancement of the DAI signal intensity has been previously examined for SAI and sonic-spray ionization, where analyte signal intensity was enhanced with as low as a 2:1 matrix-to-analyte ratio. [26][27][28] It should be noted, however, that there are differences in the experimental conditions between our work and previous studies, particularly capillary inlet temperature and solvent composition.…”

High Sensitivity Analysis of Nanoliter Volumes of Volatile and Nonvolatile Compounds using Matrix Assisted Ionization (MAI) Mass Spectrometry

“…Ambient ionization approaches have been introduced over the last decade to address needs not fulfilled by traditional ionization approaches [13]. Generally, the limits of detection (LOD) for ambient ionization methods have been reported consuming nanomole to femtomole amounts of analyte [14][15][16]. The LOD, however, is often orders of magnitude below the amount of sample required to obtain full acquisition mass spectra in which the compound of interest is the base peak in the spectrum.…”

Comparative study on ambient ionization methods for direct analysis of navel orange tissues by mass spectrometry

“…For instance, the primary ions generated by electric field (discharge/plasma) have been employed to deliver a certain amount of energy to the analytes in many ambient ionization technologies including direct analysis of real time , low‐temperature plasma , microwave plasma torch (MPT) , plasma‐assisted desorption ionization dielectric barrier discharge ionization and desorption atmospheric pressure chemical ionization (DAPCI) . Similarly, ionic species created by spray‐based technologies such as desorption electrospray ionization , probe electrospray ionization , extractive electrospray ionization , fused droplet electrospray ionization , laser ablation electrospray ionization , paper spray ionization , internal extractive electrospray ionization (iEESI) and easy ambient sonic spray ionization are utilized for transferring a relatively low amount energy to softly ionize the analytes, which is particularly beneficial for ionization of molecules with high polarity. In practical applications, understanding the featured merits, particularly the intrinsic properties associated with the sensitivity and selectivity of ionization processes, would greatly facilitate the selection of a certain ambient ionization technique for given samples.…”