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

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 abstract

Interrogating Matrix Stiffness and Metabolomics in Pancreatic Ductal Carcinoma Using an Openable Microfluidic Tumor-on-a-Chip

“…Fluorescence detection is usually the method of choice due to the ease with which fluorescence data can be obtained from microscale channel layouts . Electrochemistry also offers tools that are amenable to component miniaturization, but like fluorescence detection, it suffers from a lack of universality in addition to difficulty in decoupling high voltage detection electronics responsible for driving flow. , Neither of these sensing techniques can match the selectivity and sensitivity of MS, which offers a near universal approach to detection of small molecules. , Samples most commonly ionized by a “soft” ionization method such as electrospray ionization (ESI) are identified with minimal molecular fragmentation based on mass-to-charge ratio . Spectral methods are typically combined with chromatographic methods to obtain nearly pure fractions of chemical components from crude samples .…”

“…57,58 Neither of these sensing techniques can match the selectivity and sensitivity of MS, which offers a near universal approach to detection of small molecules. 59,60 Samples most commonly ionized by a "soft" ionization method such as electrospray ionization (ESI) 61 are identified with minimal molecular fragmentation based on mass-to-charge ratio. 62 Spectral methods are typically combined with chromatographic methods to obtain nearly pure fractions of chemical components from crude samples.…”

Analysis of double-emulsion droplets with ESI mass spectrometry for monitoring lipase-catalyzed ester hydrolysis at nanoliter scale

“…However, ESI-MS analyses of compounds in non-polar, oil-like solvents are challenging. There is unfortunately still no sufficient method to investigate chemical processes in two immiscible phases on a single-droplet level by ESI-MS [25]. In the classical macroscopic laboratory, extraction methods such as separating funnels are often used to convert reaction mixtures from non-polar organic solvents into ESI-MS compatible solutions.…”