Preliminary investigation of electrodynamic charged droplet processing to couple capillary liquid chromatography with matrix‐assisted laser desorption/ionization mass spectrometry

Bogan, Michael J.; Agnes, George R.

doi:10.1002/rcm.1670

Cited by 16 publications

(15 citation statements)

References 42 publications

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“…Note that glycerol, which was present in all starting solutions to facilitate droplet levitation, is considered detrimental to MALDI-MS analysis. The investigation of preparing MALDI sample spots by WaSP without glycerol is ongoing [21].…”

Section: Matrix-assisted Laser Desorption/ionization Mass Spectrometrymentioning

confidence: 99%

“…This observation was consistent with all combinations of two different m/z droplets levitated in the EDB (i.e., IP f,50V droplet ejected before IP f,150V ). With only two droplets that had the same m/z levitated, such as two IP f,50V , IP f,100V , or IP f,150V droplets, the trajectories of the droplets were similar and their deposition potential (DP) values were identical within experimental error [21]. Thus, two separate and complementary procedures were developed to differentiate between two different m/z droplets levitated in the EDB, facilitating further experiments designed to characterize differential chemical processing as a function of droplet net charge.…”

Section: Levitation and Ejection Of Different M/z Dropletsmentioning

confidence: 99%

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Promotion of α-cyano-4-hydroxycinnamic acid and peptide cocrystallization within levitated droplets with net charge

Bogan

Bakhoum

Agnes

2005

J. Am. Soc. Mass Spectrom.

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Many reactions occur as a result of charge imbalance within or between reactive species in reaction vessels that have zero net charge. Here, chemical processes taking place within reaction vessels having net excess charge were studied. For mass spectroscopists, a familiar example of vessels that defy electroneutrality are the charged droplets produced by an electrospray ion source. Evidence is presented that control of the magnitude of the net charge contained in a reaction vessel, in this case a levitated droplet, can be used to promote nucleation and crystal growth of a mixture of an organic acid, ␣-cyano-4-hydroxycinnamic acid (CHCA), with one or more peptides. This phenomenon was first observed during our ongoing development of wall-less sample preparation (WaSP), electrodynamic charged droplet processing methodology capable of creating micrometer-sized sample spots for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) from subnanoliter volumes of sample material. Peptide ion signal-to-noise (S/N) ratios obtained by MALDI-TOF-MS from sample spots created from droplets that had high relative magnitude of net charge were consistently greater than those detected from sample spots created from droplets that had lower net charge. To study this unexpected phenomenon further, WaSP methodology was developed to process different mass-to-charge (m/z) droplets levitated in an electrodynamic balance (EDB), facilitating their deposition onto different positions of a target to create arrays of droplet residues ordered from highest to lowest m/z. This capability allowed simultaneous levitation with subsequent separation of a population of droplets created from a single starting solution, but the droplets had varied magnitudes of net charge. After the droplets were ejected from the EDB and collected on a glass slide or MALDI plate, the solids contained in the deposited droplets were characterized using microscopy and MALDI-TOF-MS. T he physics of droplets that possess net charge is a subject that continues to receive considerable theoretical and experimental attention 140 years after initial independent studies by Lord Kelvin and Lord Rayleigh [1][2][3][4][5][6][7]. Less well characterized is the condensed phase chemistry that could occur within such droplets as a result of the net charge that is localized in the diffuse layer at the droplet-air interface [8,9]. Such chemistry could be rich. For instance, mass spectrometry studies of cluster ions released from charged droplets in an electrospray have identified shifts in chemical equilibria and the formation of preferred nanocrystalline structures [10 -14]. It is possible that these perturbations in the chemical processing are dominated by effects that transpire because the reaction vessels defy electroneutrality.Here we apply electrodynamic levitation technology [15][16][17], microscopy, and MALDI-MS to characterize chemistry that occurred within levitated droplets as a function of the magnitude of their net charge. Droplets were d...

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Section: Matrix-assisted Laser Desorption/ionization Mass Spectrometrymentioning

confidence: 99%

Section: Levitation and Ejection Of Different M/z Dropletsmentioning

confidence: 99%

Promotion of α-cyano-4-hydroxycinnamic acid and peptide cocrystallization within levitated droplets with net charge

Bogan

Bakhoum

Agnes

2005

J. Am. Soc. Mass Spectrom.

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“…The focused spot size on the plate was visualized by forming white grains of HCCA matrix on the MALDI plate. 35 As an example, a series of 1.3-mm white spots of HCCA matrix deposited on a 144-well MALDI plate is shown in Figure S1a in Supplementary Material (SM). Some measured spot sizes are listed in Table 1 as a function of geometry (A-F), tip size, applied voltage, and tip-to-plate distance (G).…”

Section: Resultsmentioning

confidence: 99%

Focused Electrospray Deposition for Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Jeong¹,

Seo²,

Yoon³

et al. 2010

Bulletin of the Korean Chemical Society

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Focused electrospray (FES) deposition method is presented for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. FES ion optics consists of two cylindrical focusing electrodes capped with a truncated conical electrode through which an electrospray emitter passes along the cylindrical axis. A spray of charged droplets is focused onto a sample well on a MALDI target plate under atmospheric pressure. The shape and size distributions of matrix crystals are visualized by scanning electron microscope and the mass spectra are obtained by time-of-flight mass spectrometry. Angiotensin II, bradykinin, and substance P are used as test samples, while α-cyano-4-hydroxycinnamic acid and dihydroxybenzoic acid are employed as matrices. FES of a sample/matrix mixture produces fine crystal grains on a 1-3 mm spot and reproducibly yields the mass spectra with little shot-to-shot and spot-to-spot variations. Although FES greatly stabilizes the signals, the space charge due to matrix ions limits the detection sensitivity of peptides. To avoid the space charge problem, we adopted a dual FES/FES mode, which separately deposits matrix and sample by FES in sequence. The dual FES/FES mode reaches the detection sensitivity of 0.88 amol, enabling ultrasensitive detection of peptides by homogeneously depositing matrix and sample under atmospheric pressure.

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“…Because of the advantages of MALDI like fast, efficient and high tolerance to nonvolatile buffers and impurities [40,41], the samples for MALDI are typically applied to solid supports and fractionated off-line with liquid or gel separations [42]. Investigators have hyphenated MALDI or desorption/ionization on porous silicon (DIOS) analysis with separation techniques such as HPLC [43], GPC [44], CE [45], TLC [46] and polyacrylamide gels [47]. Many measures like exciting samples at atmospheric pressure [48,49] or continuously streaking [50] on the target are implemented to improve the characters of off-line MALDI.…”

Section: The Separation Technologies Prior To Maldi-msmentioning

confidence: 99%

Analysis of low molecular weight compounds by MALDI-FTICR-MS

Wang

Zhao

et al. 2011

Journal of Chromatography B

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Preliminary investigation of electrodynamic charged droplet processing to couple capillary liquid chromatography with matrix‐assisted laser desorption/ionization mass spectrometry

Cited by 16 publications

References 42 publications

Promotion of α-cyano-4-hydroxycinnamic acid and peptide cocrystallization within levitated droplets with net charge

Promotion of α-cyano-4-hydroxycinnamic acid and peptide cocrystallization within levitated droplets with net charge

Focused Electrospray Deposition for Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Analysis of low molecular weight compounds by MALDI-FTICR-MS

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