Ultrasonication‐assisted spray ionization‐based micro‐reactors for online monitoring of fast chemical reactions by mass spectrometry

Abstract

Microfluidics can be used to handle relatively small volumes of samples and to conduct reactions in microliter‐sized volumes. Electrospray ionization can couple microfluidics with mass spectrometry (MS) to monitor chemical reactions online. However, fabricating microfluidic chips is time‐consuming. We herein propose the use of a micro‐reactor that is sustained by two capillaries and an ultrasonicator. The inlets of the capillaries were individually immersed to two different sample vials that were subjected to the ultrasonicator. The tapered outlets of the two capillaries were placed cross with an angle of ~60° close to the inlet of the mass spectrometer to fuse the eluents. On the basis of capillary action and ultrasonication, the samples from the two capillaries can be continuously directed to the capillary outlets and fuse simultaneously to generate gas phase ions for MS analysis through ultrasonication‐assisted spray ionization (UASI). Any electric contact applied on the capillaries is not required. Nevertheless, UASI spray derived from the eluents can readily occur in front of the mass spectrometer. That is, a micro‐reactor was created from the fusing of the eluent containing different reactants from these two UASI capillaries, allowing reactions to be conducted in situ. The solvent in the fused droplets was evaporated quickly, and the product ions could be immediately observed by MS because of the extreme rise in the concentration of the reactants. For proof of concept, pyrazole synthesis reaction and cortisone derivatization by Girard T reagent were selected as the model reactions. The results demonstrated the feasibility of using UASI‐based micro‐reactor for online MS analysis to detect reaction intermediates and products.

Stochastic Dynamic Mass Spectrometric Quantitative and Structural Analyses of Pharmaceutics and Biocides in Biota and Sewage Sludge

“…Analytical mass spectrometry is a complex term, referring to three major research tasks of qualitative , quantitative , and structural analyses . However, pursuing the exact chemometrics (|r| = 1) is a challenging analytical task [ 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. Among theoretical model equations that are particularly relevant are those producing exact method performance.…”

Chemical Reaction Monitoring by Ambient Mass Spectrometry

“…For example, Chen and coworkers described a ultrasound-assisted spray ionization (UASI) for the complementary detection of biomacromolecules without post-ionization such as sonic spray ionization (SSI) (Chen et al, 2010b). Low-frequency ultrasound could support the desorption of analytes without chemical changes in molecules (Chen et al, 2010a(Chen et al, , 2019a and are more suitable for the online monitoring of reactions performed under ultrasonication (Lin et al, 2014). Many excellent ion sources, such as VUV lamp-based chargetransfer ionization (VUV lamp-based CTI) (Hua et al, 2011), gravitational sampling electrospray ionization (GS-ESI) (Hsu et al, 2014) and contactless atmospheric pressure ionization (C-API-MS) (Hsieh et al, 2012), have recently been reported for online reaction monitoring, which would also be prospective for further developments.…”

Utilizing a Metal Inlet Coiled with Copper Wire as the Ion Source for Ambient Ionization Mass Spectrometry

“…[23][24][25][26]35,42 These approaches are called as field-induced 21 or contactless ionization methods. [23][24][25][26][27][29][30][31][35][36][37][38][39][40]42 For example, when a small piece of insulating fiber 23 or one piece of electric conductive material 25,26,39 was placed close to the metal inlet of the mass spectrometer, which was applied with a high voltage, volatiles or semivolatiles derived from the solid sample deposit on the fiber could be readily ionized and detected by the mass spectrometer. Corona discharge-like processes occur to initiate the ionization of volatiles and semivolatiles derived from the sample, although no direct electric contact was applied on the ionization emitter.…”