Online monitoring of chemical reactions by contactless atmospheric pressure ionization mass spectrometry

Abstract

Online monitoring of the appearance of the intermediates and products during chemical reactions is helpful to understand reaction mechanisms. Various analytical tools including nuclear magnetic resonance spectroscopy, [1,2] Raman spectroscopy [3,4] and mass spectrometry (MS) have been employed for the study. MS is one of the most promising means among analytical tools that can provide information of mass-to-charge ratios for intermediates and products generated from chemical reactions.

Going beyond electrospray: mass spectrometric studies of chemical reactions in and on liquids

“…By placing one end of a fused silica capillary into a sealed reaction flask with a slight over pressure and putting the other end in front of an MS inlet, Hsieh et al were able to detect ions from solution and monitor the deesterification of a protected sugar. 41 The over pressure induced flow through the tubing in the range of nL min –1 . In this case, the voltage at the MS inlet was believed to induce ionization.…”

Syringe Infusion-based Contactless Atmospheric Pressure Ionization Mass Spectrometry for Small and Large Biomolecules

“…30,31 We still consider the present approach as C-API because no external electric connection on the capillary emitter was applied. .…”

“…1−29 The key features of recently developed API are speed and simplicity through the reduction of time-consuming sample preparation steps and minimization of the components required to fabricate ion sources. 24−29 We recently explored contactless API (C-API) 30 (or contactless electrospray ionization (C-ESI)), 31 which uses a tapered capillary as the sampling tube and spray emitter without the application of any external electric voltage. Capillary action is the initial driving force that directs the sample from the inlet to the outlet.…”

“…We previously demonstrated that application of a balloon filled with nitrogen gas in the sample inlet can accelerate the flow rate for introduction of the C-API sample. 31 However, the balloon may gradually lose gas, leading to reductions in the flow rate. Thus, we herein alternatively use a syringe pump to provide a given flow rate to direct the sample solution from the capillary inlet to the proximity of the mass spectrometer for polarization and ionization to occur.…”

Electrospray Modifications for Advancing Mass Spectrometric Analysis

“…Due to this simplistic nature, C-API has been demonstrated to be suitable for monitoring online chemical reactions. 85) e C-API ion source could also be used for multiple sample analysis by an automated movement of stage beneath the capillary. 86) In a similar setup, Chang and co-workers used the capillary action to sample liquids present in plant parts and their subsequent ionization to study bioactive compounds.…”