On-chip mass spectrometric analysis in non-polar solvents by liquid beam infrared matrix-assisted laser dispersion/ionization

Raphael D. Urban,Ales Charvat,Detlev Belder,Konstantin Wink,Stefan Ohla,Benjamin Krafft,Kirsten Zeitler,Bernd Abel,Tillmann G. Fischer

doi:10.1007/s00216-020-03115-4

Raphael D. Urban, Ales Charvat + Show 7 more

Open Access

https://doi.org/10.1007/s00216-020-03115-4

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Abstract

By the on-chip integration of a droplet generator in front of an emitter tip, droplets of non-polar solvents are generated in a free jet of an aqueous matrix. When an IR laser irradiates this free liquid jet consisting of water as the continuous phase and the non-polar solvent as the dispersed droplet phase, the solutes in the droplets are ionized. This ionization at atmospheric pressure enables the mass spectrometric analysis of non-polar compounds with the aid of a surrounding aqueous matrix that absorbs IR light. This works both for non-polar solvents such as n-heptane and for water non-miscible solvents like chloroform. In a proof of concept study, this approach is applied to monitor a photooxidation of N-phenyl-1,2,3,4-tetrahydroisoquinoline.Graphical abstractBy using water as an infrared absorbing matrix, analytes, dissolved in non-polar solvents from reactions carried out on a microchip, can be desorbed and ionized for investigation by mass spectrometry.

Highlights

There has been significant progress in coupling microfluidic chips with mass spectrometry (MS) [1,2,3,4]
We have recently shown that liquid beam desorption mass spectrometry is an exciting alternative to electrospray ionization for microfluidic chips coupling with mass spectrometry [50]
In order to produce stroboscopic images, the liquid jet was positioned between a light-emitting diode (LED) (KINGSO 5 mm, white) and a self-designed mobile microscope (Thorlabs Inc., Newton, NJ, USA), already described in a previous publication, with a camera connected to it (FLIR Flea 3, FL3-U3-20e4M-C, FLIR Systems, Inc., OR, USA) [8]

Summary

Introduction

There has been significant progress in coupling microfluidic chips with mass spectrometry (MS) [1,2,3,4]. ESI can be seamlessly integrated on microfluidic devices by the incorporation of an emitter tip This chip-ESI/ MS technology has been widely applied for coupling various microfluidic applications and corresponding devices to mass spectrometry such as chip electrophoresis [5,6,7], chip chromatography [8,9,10], microfluidic reaction devices [11,12,13,14], droplet microfluidics [12, 15,16,17,18,19], digital microfluidics [20,21,22], and paper-based devices [23,24,25,26].

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