Dual-channel electrospray microchip

3D-Printed Microfluidic Nanoelectrospray Ionization Source Based on Hydrodynamic Focusing

Nanoelectrospray ionization (nESI) mass spectrometry (MS) is an ideal detection method for microfluidic chips, and its performances depend on nESI emitters. However, the fabrication of monolithic nESI emitters in chips was difficult. Herein, we propose a three-dimensional (3D) printing method to develop a microfluidic nanoelectrospray ionization source (NIS), composed of a nESI emitter and other components. Firstly, the NIS was compatible with a 50 - 500 nL min^-1 nanoflows by imposing 3D hydrodynamic focusing to compensate for the total flow rate, achieving a 7.2% best relative standard deviation in the total ion current (TIC) profiles. Additionally, it was applied to probe thirteen organic chemicals, insulin, and lysozyme with adequate signal-to-noise ratios and an accuracy of m/z between 9.02 × 10^-1 and 1.48 × 10³ ppm. Finally, the NIS achieved comparable limits of detection compared with its commercial counterpart. Considering the standardized preparation of NIS, it would be a potential option to develop 3D-printed customized Chip-MS platforms.

Coaxial Electrospray Ionization for the Study of Rapid In-source Chemistry

Coaxial electrospray has been used effectively for several dual-emitter applications, but has not been utilized for the study of rapid in-source chemistry. In this paper, we report the fabrication of a coaxial, micro-volume dual-emitter through the modification of a manufacturer's standard electrospray probe. This modification creates rapid mixing inside the Taylor cone and the ability to manipulate fast reactions using a variety of solvents and analytes. We demonstrate its potential as a low-cost, dual-emitter assembly for diverse applications through three examples: relative ionization in a biphasic electrospray, hydrogen-deuterium exchange, and protein supercharging. Graphical Abstract.

Multi-channel microfluidic chip coupling with mass spectrometry for simultaneous electro-sprays and extraction

Considering the advantages and research status of microfluidic chip coupling with mass spectrometry (MS), a microfluidic chip-based multi-channel ionization (MCMCI) for the extraction of untreated compounds in complex matrices without sample pretreatments was developed. Quantitative analysis of human urine spiked with various rhodamine B concentrations was also performed, and good linearity was obtained. Comparing to the macro ionization device, MCMCI significantly improved the integration of ionization source, simplified the operation of such a device, and greatly increased the signal intensity with much lower gas pressure. Comparison of our MCMCI with two and three gas channels indicated that the liquid–liquid extraction process before spraying and after spraying produced similar MS results. Moreover, this MCMCI with three gas channels also implemented simultaneous dual sprays with high DC voltages, the interference of two samples was minor and ion suppression effect was drastically alleviated. Such advantages may easily enable internal calibration for accurate mass measurement. Furthermore, dual extraction can be implemented by integrating such multi-spray configuration, which can improve the extracted signal intensity and sensitivity. These technologies open up new avenues for the application of microfluidic chip coupling with MS.

Three-dimensional hydrodynamic focusing microfluidic emitter: a strategy to inhibit sample ion expansion in nanoelectrospray ionization

A proposed 3D HFNE was used to generate a wrapped electrospray to achieve the inhibition of sample ion expansion, thus restraining injection loss in electrospray ionization.

A multichannel rotating electrospray ionization mass spectrometry (MRESI): instrumentation and plume interactions

A multichannel rotating electrospray ionization (MRESI) mass spectrometry method is described. Plume interactions are also systematically studied.

Microfluidics-to-mass spectrometry: a review of coupling methods and applications

Microfluidic devices offer great advantages in integrating sample processes, minimizing sample and reagent volumes, and increasing analysis speed, while mass spectrometry detection provides high information content, is sensitive, and can be used in quantitative analyses. The coupling of microfluidic devices to mass spectrometers is becoming more common with the strengths of both systems being combined to analyze precious and complex samples. This review summarizes select achievements published between 2010 and July 2014 in novel coupling between microfluidic devices and mass spectrometers. The review is subdivided by the types of ionization sources employed, and the different microfluidic systems used.

Induced dual-nanospray: a novel internal calibration method for convenient and accurate mass measurement

Accurate mass information is of great importance in the determination of unknown compounds. An effective and easy-to-control internal mass calibration method will dramatically benefit accurate mass measurement. Here we reported a simple induced dual-nanospray internal calibration device which has the following three advantages: (1) the two sprayers are in the same alternating current field; thus both reference ions and sample ions can be simultaneously generated and recorded. (2) It is very simple and can be easily assembled. Just two metal tubes, two nanosprayers, and an alternating current power supply are included. (3)With the low-flow-rate character and the versatility of nanoESI, this calibration method is capable of calibrating various samples, even untreated complex samples such as urine and other biological samples with small sample volumes. The calibration errors are around 1 ppm in positive ion mode and 3 ppm in negative ion mode with good repeatability. This new internal calibration method opens up new possibilities in the determination of unknown compounds, and it has great potential for the broad applications in biological and chemical analysis.