Droplet characterization of high-flowrate water electrospray using shadowgraph image analysis

Jung, Minkyu; Kim, Soyeon; Lim, Jihun; Lee, Jinwook; Jeong, Seo Young; Ku, Donik; Na, Sun-Ik; Kim, Min Soo

doi:10.1007/s12206-022-0346-9

Cited by 4 publications

(2 citation statements)

References 23 publications

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“…In addition, the PDA setup for investigation of electrospray required a laser source and detector placed in an opposite direction of the detected area. 61 Because the observed electrospray droplets are transparent, PDA was used in the refraction mode. However, in the current study�involving real-time droplet observations during MS analysis�there are geometrical constraints due to the small size of the ion source chamber, which precludes positioning large devices on both sides of the electrospray emitter.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Therefore, PDA may not be applicable to a study such as the current one, in which the entire electrospray packet needs to be interrogated and the imaging result needs to be correlated with the MS result. In addition, the PDA setup for investigation of electrospray required a laser source and detector placed in an opposite direction of the detected area . Because the observed electrospray droplets are transparent, PDA was used in the refraction mode.…”

Section: Results and Discussionmentioning

confidence: 99%

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Are Most Micrometer Droplets (>10 μm) Wasted in Electrospray Ionization? An Insight from Real-Time High-Speed Imaging

Hsu,

Prabhu,

Chang

et al. 2023

Anal. Chem.

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Electrospray ionization (ESI) is one of the main techniques used in mass spectrometry (MS) of nonvolatile compounds. ESI is a disordered process, in which a large number of polydisperse droplets are projected from a fluctuating Taylor cone and jet protruding ESI emitter. Here, we disclose a system for sectioning electrospray plumes to discrete packets with millisecond and submillisecond lifetime, which are introduced to the MS orifice, one at a time. A high-speed camera was triggered at 10,000 frames per second to capture consecutive images of the electrospray packets transmitted to the mass spectrometer. We further correlated the high-speed images of electrospray packets with MS signals of a test analyte (acetaminophen). Following computational treatment of the images, we determined the number of droplet observations (<300), average diameter of droplets (∼10–20 μm), and average volume of droplets (few tens of picoliters) in the individual electrospray packets. The result shows that most micrometer droplets (>10 μm) do not have any significant contribution to the MS signals. This finding is in agreement with the prior conjecture that most of the MS signals are mainly attributed to nanodroplets. Based on this finding, one can deduce that only a small number of the initial microdroplets effectively carry analyte molecules that undergo ionization. We discuss that, in future, one may propose a way to “recharge” the emitted initial micrometer droplets to increase the efficiency of conventional ESI setups.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Are Most Micrometer Droplets (>10 μm) Wasted in Electrospray Ionization? An Insight from Real-Time High-Speed Imaging

Hsu,

Prabhu,

Chang

et al. 2023

Anal. Chem.

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Does the Formation of a Taylor Cone in a Pulsating Electrospray Directly Impact Mass Spectrometry Signals?

Chang,

Urban

2024

ACS Omega

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Electrospray ionization (ESI) remains the dominant technique in mass spectrometry (MS)-based analyses. Here, we investigated the relationship between a crucial aspect of ESI, the formation of the Taylor cone, and the MS ion current by utilizing a triple quadrupole (QqQ) mass spectrometer coupled with a streaming high-speed camera and a 3-ring electrode system. In one test, ion current over a 30-s plume gate (a ring electrode) opening was compared with the Taylor cone occurrence analyzed offline, with Spearman's correlation coefficients consistently near 0 despite parameter variations. In another test, real-time detection of Taylor cones was synchronized with QqQ-MS, selectively opening (de-energizing) the plume gate based on the Taylor cone status. This approach enabled matching the ion current with the Taylor cone occurrence. There was no apparent difference between the MS signals recorded in the presence and absence of a Taylor cone. Additionally, a Faraday plate was employed as a detector in offline experiments, revealing agreement between the frequency of liquid meniscus (Taylor cone) oscillation (∼1.92 kHz)�measured by high-speed imaging�and the frequency of spray current (∼1.93 kHz). We suggest that the lack of positive correlations in the MS experiments is due to intrinsic ion carryover during transit from the ion source to the detector and due to the insufficient data acquisition rate of the mass spectrometer, which erases short-term fluctuations of ion current.

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Object tracking based droplet characterization of high flowrate electrospray

Jung

Kim

et al. 2023

Physics of Fluids

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Electrospray was applied to the wet electrostatic precipitator to reduce the water consumption of high-efficiency fine dust collection. The size of droplets must be large to avoid evaporating quickly under high temperature exhaust gas conditions, so a high flowrate condition of several milliliters/min is used, which is relatively high compared with previous applications. Because high flowrate electrospray has a wide spray range and low spray density, image-based droplet size measurement was used. A bias in the probability in the distribution occurs because of the difference in velocity between the droplets. In this study, an approach with object tracking was suggested to eliminate the bias from velocity differences. High flowrate electrospray droplets under various voltage conditions were visualized with a high-speed camera. Based on the image processing, the corrected distribution was characterized, and the effect of the bias was established through comparison with the general distribution. In addition, the spray pattern and the droplet distribution according to the applied voltage of three spraying modes were analyzed. Improved analysis of the actual spray using this approach will guide the selection of operating conditions that optimize dust collection efficiency.

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Droplet characterization of high-flowrate water electrospray using shadowgraph image analysis

Cited by 4 publications

References 23 publications

Are Most Micrometer Droplets (>10 μm) Wasted in Electrospray Ionization? An Insight from Real-Time High-Speed Imaging

Are Most Micrometer Droplets (>10 μm) Wasted in Electrospray Ionization? An Insight from Real-Time High-Speed Imaging

Does the Formation of a Taylor Cone in a Pulsating Electrospray Directly Impact Mass Spectrometry Signals?

Object tracking based droplet characterization of high flowrate electrospray

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