How electrospray potentials can disrupt droplet microfluidics and how to prevent this

Peretzki, Andrea J.; Schmidt, Sabine; Flachowsky, Elias; Das, Anish; Gerhardt, Renata; Belder, Detlev

doi:10.1039/d0lc00936a

Cited by 17 publications

(14 citation statements)

References 64 publications

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“…In first experiments, we tried to use a steel capillary that facilitates electrical contact to build up the required electrospray potential at the tip. In addition to previous observations that the electrospray potential can disrupt the droplet flow, 37 we documented splitting and coalescence of the nL-sized droplets when they passed through the metal emitters (see microscopic images in Figure S3). Moreover, steel emitters have been reported to show increased carryover effects.…”

Section: ■ Experimental Sectionsupporting

confidence: 73%

“…■ RESULTS AND DISCUSSION Development of an ESI-IMS Platform for the Detection of Droplet Microfluidics. Encouraged by our experience with the coupling of droplet microfluidics with mass spectrometric detection, 18,33,35,37 as well as the recently realized coupling of chip chromatography with IMS, 38,39 we aimed in this work to explore the potential of IMS for droplet analysis. Therefore, a custom-built drift tube IMS with shifted potentials 62 was employed as a detector, which was modified with two SST inlets.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…Especially the continuous spraying of water-in-oil dispersions, as it is the case in inline droplet microfluidics, is a special strain on the MS devices. In our own experience, ,,, this issue is well justified because the carrier oil phase as well as the surfactants can contaminate the mass spectrometer, e.g., the ion optics in the high-vacuum range, which leads to regular cleaning and maintenance work. Since the mass spectrometer must be vented for this purpose, this results in long downtimes.…”

Section: Introductionmentioning

confidence: 99%

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Coupling Droplet Microfluidics with Ion Mobility Spectrometry for Monitoring Chemical Conversions at Nanoliter Scale

et al. 2021

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We introduce the coupling of droplet microfluidics and ion mobility spectrometry (IMS) to address the challenges of label-free and chemical-specific detection of compounds in individual droplets. In analogy to the established use of mass spectrometry, droplet−IMS coupling can be also achieved via electrospray ionization but with significantly less instrumental effort. Because IMS instruments do not require high-vacuum systems, they are very compact, cost-effective, and robust, making them an ideal candidate as a chemical-specific end-of-line detector for segmented flow experiments. Herein, we demonstrate the successful coupling of droplet microfluidics with a custom-built high-resolution drift tube IMS system for monitoring chemical reactions in nL-sized droplets in an oil phase. The analytes contained in each droplet were assigned according to their characteristic ion mobility with limit of detections down to 200 nM to 1 μM and droplet frequencies ranging from 0.1 to 0.5 Hz. Using a custom sheath flow electrospray interface, we have further achieved the chemical-specific monitoring of a biochemical transformation catalyzed by a few hundred yeast cells, at single droplet level.

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Section: ■ Experimental Sectionsupporting

confidence: 73%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coupling Droplet Microfluidics with Ion Mobility Spectrometry for Monitoring Chemical Conversions at Nanoliter Scale

et al. 2021

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“…This benefitted from the rich literature of droplet microfluidics (e.g., droplet generation 28 , picoinjection 29 , phase extraction [30][31][32] , etc.). These solutions, which were extensively covered in recent reviews [33][34][35][36] , comprise in-flow electrochemical chips 37,38 , fluorescent assays 23,39,40 and include many developments of electrophoretic 30,41 and mass spectrometry methods 26,[42][43][44][45][46][47][48] .…”

Section: Introductionmentioning

confidence: 99%

On demand nanoliter sampling probe for collection of brain fluid

Teixidor

Novello

Ortiz

et al. 2022

Preprint

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Continuous fluidic sampling systems allow collection of brain biomarkers in vivo. Here, we propose a new sampling paradigm, Droplet on Demand (DoD), implemented in a microfabricated neural probe. It allows sampling droplets loaded with molecules from the brain extracellular fluid punctually, without the long transient equilibration periods typical of continuous methods. It uses an accurate fluidic sequence and correct operation is verified by the embedded electrodes. As a proof of concept, we demonstrated the application of this novel approach in vitro and in vivo, to collect glucose in the brain of mice, with a temporal resolution of 1-2 minutes and without transient regime. Absolute quantification of the glucose level in the samples was performed by direct infusion nanoelectrospray ionization Fourier transform mass spectrometry (nanoESI-FTMS). By adjusting the diffusion time and the perfusion volume of DoD, the fraction of molecules recovered in the samples can be tuned to mirror the tissue concentration at accurate points in time. This makes quantification of biomarkers in the brain possible within acute experiments of only 20 to 120 minutes. DoD provides a complementary tool to continuous microdialysis and push-pull sampling probes. The advances allowed by DoD will benefit quantitative molecular studies in the brain, namely for molecules involved in volume transmission or for protein aggregates that form in neurodegenerative diseases over long periods.

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“…First, to achieve efficient ionization for low picoliter-scale volumes, droplets need to be generated and sprayed at lower flow rates, even down to nL/min, to maximize the ionization efficiency − and match the scan speed of spectrometers . Other properties, including surface tension, carrier oils, sample concentration, and electrospray potentials, also have a strong influence on the droplet generation, spray stability, and ionization efficiency of analytes in nESI-MS . In addition, most droplet generators reported previously have been connected to external ESI emitters, which may introduce dead volumes and sample loss in the connecting tubes.…”

mentioning

confidence: 99%

Attomole-Level Multiplexed Detection of Neurochemicals in Picoliter Droplets by On-Chip Nanoelectrospray Ionization Coupled to Mass Spectrometry

Zhang

Zhao

et al. 2022

Anal. Chem.

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While droplet microfluidics is becoming an effective tool for biomedical research, sensitive detection of droplet content is still challenging, especially for multiplexed analytes compartmentalized within ultrasmall droplets down to picoliter volumes. To enable such measurements, we demonstrate a silicon-based integrated microfluidic platform for multiplexed analysis of neurochemicals in picoliter droplets via nanoelectrospray ionization (nESI)-mass spectrometry (MS). An integrated silicon microfluidic chip comprising downscaled 7 μm-radius channels, a compact T-junction for droplet generation, and an integrated nESI emitter tip is used for segmentation of analytes into picoliter compartments and their efficient delivery for subsequent MS detection. The developed system demonstrates effective detection of multiple neurochemicals encapsulated within oil-isolated plugs down to low picoliter volumes. Quantitative measurements for each neurochemical demonstrate limits of detection at the attomole level. Such results are promising for applications involving label-free and small-volume detection for monitoring a range of brain chemicals.

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How electrospray potentials can disrupt droplet microfluidics and how to prevent this

Abstract: By shielding the micro droplets from the electrospray potential, negative influences on the droplet formation and movement can be prevented.

Cited by 17 publications

References 64 publications

Coupling Droplet Microfluidics with Ion Mobility Spectrometry for Monitoring Chemical Conversions at Nanoliter Scale

Coupling Droplet Microfluidics with Ion Mobility Spectrometry for Monitoring Chemical Conversions at Nanoliter Scale

On demand nanoliter sampling probe for collection of brain fluid

Attomole-Level Multiplexed Detection of Neurochemicals in Picoliter Droplets by On-Chip Nanoelectrospray Ionization Coupled to Mass Spectrometry

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