Ion formation in droplet‐assisted ionization

Apsokardu, Michael J.; Kerecman, Devan E.; Johnston, Murray V.

doi:10.1002/rcm.8227

Cited by 21 publications

(53 citation statements)

References 28 publications

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“…16 In a subsequent study, the role of droplet size was explored for liquid droplets composed of poly(propylene glycol) (PPG). 17 In this experiment, PPG served both as the analyte and the solvent, and it was shown that the ion signal intensity scaled approximately with d 4 , where d = droplet diameter. This result suggested that droplet size as well as analyte mass flow affects the ion signal.…”

Section: ■ Results and Discussionmentioning

confidence: 77%

“…Salt contamination has been noted previously. 16,17 In separate MSMS experiments, cluster ions were examined by ramping the collision energy. Only a very low collision energy (<10 eV) was needed to break apart the clusters, showing that they are noncovalently bound.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…16 The inlet consists of a simple temperature-controlled stainlesssteel capillary. 16,17 Pressure and temperature gradients across the capillary cause liquid droplets in the gas flow to break up in a manner that produces molecular ions. The highest ion yields are obtained with aqueous droplets, 17 and the sensitivity is sufficient for atmospheric aerosols, where the mass concentration can be lower than 1 μg m −3 .…”

Section: ■ Introductionmentioning

confidence: 99%

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Online Characterization of Organic Aerosol by Condensational Growth into Aqueous Droplets Coupled with Droplet-Assisted Ionization

et al. 2021

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Online analysis of ultrafine (<100 nm diameter) particles was performed by sending the aerosol through a condensation growth chamber (CGC) to create micrometer-size aqueous droplets that were subsequently analyzed by mass spectrometry with droplet-assisted ionization (DAI). Three experiments are reported which illustrate key performance characteristics of the method and give insight into the ion formation process: size-selected cortisone particles, size-selected secondary organic aerosol (SOA) particles, and freshly nucleated SOA under atmospherically relevant conditions. In each case, SOA was produced by α-pinene ozonolysis. For size-selected cortisone particles between 30 and 90 nm diameter and SOA particles between 30 and 70 nm, the ion signal intensity was found to be approximately independent of particle size. This observation is attributed to the formation of aqueous droplets in the CGC whose size distribution is independent of the original particle size. A consequence of this behavior is that the sensitivity of molecular detection increases as the particle size decreases, and the method is particularly well suited for new particle formation studies under atmospherically relevant conditions. This aspect of the CGC−DAI method was illustrated by the online analysis of freshly nucleated SOA samples with median diameters, number concentrations, and mass concentrations on the order of 25 nm, 10 4 cm −3 , 0.2 μg m −3 , respectively. Mass spectra of freshly nucleated SOA could be explained by condensation of highly oxidized molecules (HOMs) that subsequently reacted in the particle phase. Size-selected SOA showed increasing oligomerization with increasing particle size, which is consistent with established particle growth mechanisms.

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Section: ■ Results and Discussionmentioning

confidence: 77%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Online Characterization of Organic Aerosol by Condensational Growth into Aqueous Droplets Coupled with Droplet-Assisted Ionization

et al. 2021

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“…73 This group also conducted fundamental research relating to these processes. 74 retrofitted a 266 nm laser on a high-vacuum time-of-flight (TOF) mass spectrometer and produced ESI-like charge states of insulin using 3-NBN as matrix, while the typical 355 nm laser experiments failed to produce analyte ions. 33 The matrix 3-NBN has absorption at 266 nm so that one must expect that the thermal energy required for new ionization processes operated under high vacuum is placed into the system through the use of a laser under these nearly collision-free conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The Johnston group developed droplet‐assisted inlet ionization for aerosol analysis applying an inlet tube heated as high as 850 °C without observing analyte fragmentation 73 . This group also conducted fundamental research relating to these processes 74 . In collaborative work, Ni (Academia Sinica, Taipei, Taiwan) and Weidner (Federal Institute for Materials Research and Testing, Berlin, Germany) retrofitted a 266 nm laser on a high‐vacuum time‐of‐flight (TOF) mass spectrometer and produced ESI‐like charge states of insulin using 3‐NBN as matrix, while the typical 355 nm laser experiments failed to produce analyte ions 33 .…”

Section: Introductionmentioning

confidence: 99%

An overview of biological applications and fundamentals of newinletandvacuumionization technologies

Trimpin

Marshall

Karki

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale The developments of new ionization technologies based on processes previously unknown to mass spectrometry (MS) have gained significant momentum. Herein we address the importance of understanding these unique ionization processes, demonstrate the new capabilities currently unmet by other methods, and outline their considerable analytical potential. Methods The inlet and vacuum ionization methods of solvent‐assisted ionization (SAI), matrix‐assisted ionization (MAI), and laserspray ionization can be used with commercial and dedicated ion sources producing ions from atmospheric or vacuum conditions for analyses of a variety of materials including drugs, lipids, and proteins introduced from well plates, pipet tips and plate surfaces with and without a laser using solid or solvent matrices. Mass spectrometers from various vendors are employed. Results Results are presented highlighting strengths relative to ionization methods of electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization. We demonstrate the utility of multi‐ionization platforms encompassing MAI, SAI, and ESI and enabling detection of what otherwise is missed, especially when directly analyzing mixtures. Unmatched robustness is achieved with dedicated vacuum MAI sources with mechanical introduction of the sample to the sub‐atmospheric pressure (vacuum MAI). Simplicity and use of a wide array of matrices are attained using a conduit (inlet ionization), preferably heated, with sample introduction from atmospheric pressure. Tissue, whole blood, urine (including mouse, chicken, and human origin), bacteria strains and chemical on‐probe reactions are analyzed directly and, especially in the case of vacuum ionization, without concern of carryover or instrument contamination. Conclusions Examples are provided highlighting the exceptional analytical capabilities associated with the novel ionization processes in MS that reduce operational complexity while increasing speed and robustness, achieving mass spectra with low background for improved sensitivity, suggesting the potential of this simple ionization technology to drive MS into areas currently underserved, such as clinical and medical applications.

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Direct sub‐atmospheric pressure ionization mass spectrometry: Evaporation/sublimation‐driven ionization is amazing, fundamentally, and practically

Trimpin,

Inutan,

Pagnotti

et al. 2024

J Mass Spectrom

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This paper covers direct sub‐atmospheric pressure ionization mass spectrometry (MS). The discovery, applications, and mechanistic aspects of novel ionization processes for use in MS that are not based on the high‐energy input from voltage, laser, and/or high temperature but on sublimation/evaporation within a region linking a higher to lower pressure and modulated by heat and collisions, are discussed, including how this new reality has guided a series of discoveries, instrument developments, and commercialization. A research focus, inter alia, is on how best to understand, improve, and use these novel ionization processes, which convert volatile and nonvolatile compounds from solids (sublimation) or liquids (evaporation) into gas‐phase ions for analysis by MS providing reproducible, accurate, sensitive, and prompt results. Our perception on how these unprecedented versus traditional ionization processes/methods relate to each other, how they can be made to coexist on the same mass spectrometer, and an outlook on new and expanded applications (e.g., clinical, portable, fast, safe, and autonomous) is presented, and is based on ST's Opening lecture presentation at the Nordic Mass spectrometry Conference, Geilo, Norway, January 2023. Focus will be on matrix‐assisted ionization (MAI) and solvent‐assisted ionization (SAI) MS covering the period from 2010 to 2023; a potential paradigm shift in the making.

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Ion formation in droplet‐assisted ionization

Cited by 21 publications

References 28 publications

Online Characterization of Organic Aerosol by Condensational Growth into Aqueous Droplets Coupled with Droplet-Assisted Ionization

Online Characterization of Organic Aerosol by Condensational Growth into Aqueous Droplets Coupled with Droplet-Assisted Ionization

An overview of biological applications and fundamentals of newinletandvacuumionization technologies

Direct sub‐atmospheric pressure ionization mass spectrometry: Evaporation/sublimation‐driven ionization is amazing, fundamentally, and practically

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