Atmospheric Pressure Ionization (API) Mass Spectrometry. Solvent-Mediated Ionization of Samples Introduced in Solution and in a Liquid Chromatograph Effluent Stream

Horning, E. C.; Carroll, D. I.; Džidić, I.; Haegele, K. D.; Horning, M. G.; Stillwell, Richard

doi:10.1093/chromsci/12.11.725

Cited by 186 publications

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“…It is important to note that the additional electrodes and heater, which are used in the commercial DART, were excluded to investigate fundamental properties of the discharge. The G-A (FAPA-like) discharge, labeled with a blue arrow in Figure 2, was operated with a ballast resistance of 1.5 k⍀ and operated at 25 mA and Ϫ450 V. Helium metastables, along with other discharge products, exit the cell through the small hole in the anode, and ionize N 2 and H 2 O in open air, resulting in the production of reagent ions [4,16,17]. The voltage of the anode was adjusted with a low-voltage DC power supply (model 6299A; Hewlett Packard, Palo Alto, CA) to maintain a field-free sampling region between the discharge cell and the mass spectrometer interface when mass spectrometry was performed.…”

Section: Instrumentationmentioning

confidence: 99%

“…The glow discharge (GD), which has conventionally been operated between 0.1 to 10 Torr, exists at much lower currents (tens of milliamperes) and a higher voltage drop (hundreds of volts). Lastly, the corona discharge operates with very low currents (a few microamperes) and a much higher voltage drop (several kilovolts).Corona discharges find their most common analytical application in atmospheric pressure chemical ionization (APCI) [4,5]. In conventional APCI, a corona discharge is formed by applying ϳ4 kV to a needle electrode in a selected atmosphere, to yield currents of ϳ5 A.…”

mentioning

confidence: 99%

“…Corona discharges find their most common analytical application in atmospheric pressure chemical ionization (APCI) [4,5]. In conventional APCI, a corona discharge is formed by applying ϳ4 kV to a needle electrode in a selected atmosphere, to yield currents of ϳ5 A.…”

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Characterization of direct-current atmospheric-pressure discharges useful for ambient desorption/ionization mass spectrometry

Shelley

Wiley

Chan

et al. 2009

J. Am. Soc. Mass Spectrom.

122

133

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Two relatively new ambient ionization sources, direct analysis in real time (DART) and the flowing atmospheric-pressure afterglow (FAPA), use direct current, atmospheric-pressure discharges to produce reagent ions for the direct ionization of a sample. Although at a first glance these two sources appear similar, a fundamental study reveals otherwise. Specifically, DART was found to operate with a corona-to-glow transition (C-G) discharge whereas the FAPA was found to operate with a glow-to-arc transition (G-A) discharge. The characteristics of both discharges were evaluated on the basis of four factors: reagent-ion production, response to a model analyte (ferrocene), infrared (IR) thermography of the gas used for desorption and ionization, and spatial emission characteristics. The G-A discharge produced a greater abundance and a wider variety of reagent ions than the C-G discharge. In addition, the discharges yielded different adducts and signal strengths for ferrocene. It was also found that the gas exiting the discharge chamber reached a maximum of 235°C and 55°C for the G-A and C-G discharges, respectively. Finally, spatially resolved emission maps of both discharges showed clear differences for N 2 ϩ and O(I). These findings demonstrate that the discharges used by FAPA and DART are fundamentally different and should have different optimal applications for ambient desorption/ionization mass spectrometry (ADI-MS). irect-current (DC) discharges have been widely used for elemental analyses since they were first introduced for alloy characterization [1]. When DC discharges were coupled with mass spectrometry, the result was a very sensitive and powerful tool for elemental [1] and molecular analyses [2,3]. Of the many electrical regimes of DC discharges, three forms have been found to have particular analytical merit: the arc, the glow, and the corona. Among these three types of discharges, the fundamental distinction is the operating current and voltage. The arc occurs at very high currents (hundreds of amperes) with a low voltage drop between electrodes (tens of volts). It also exhibits negative resistance; that is, the sustaining voltage drops as the current rises. The glow discharge (GD), which has conventionally been operated between 0.1 to 10 Torr, exists at much lower currents (tens of milliamperes) and a higher voltage drop (hundreds of volts). Lastly, the corona discharge operates with very low currents (a few microamperes) and a much higher voltage drop (several kilovolts).Corona discharges find their most common analytical application in atmospheric pressure chemical ionization (APCI) [4,5]. In conventional APCI, a corona discharge is formed by applying ϳ4 kV to a needle electrode in a selected atmosphere, to yield currents of ϳ5 A. After a series of reactions [5], reagent ions are produced that can then ionize a sample. Protonated water clusters are typically observed because of the presence of water vapor in the air. Such protonated clusters promote proton transfer ionization, resulting in mass spect...

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Section: Instrumentationmentioning

confidence: 99%

mentioning

confidence: 99%

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Characterization of direct-current atmospheric-pressure discharges useful for ambient desorption/ionization mass spectrometry

Shelley

Wiley

Chan

et al. 2009

J. Am. Soc. Mass Spectrom.

122

133

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“…Only compounds more basic than ammonia or compounds capable of stable gas-phase attachment of NH 4 ϩ are°observed. The sensitivity of GC/APMS in the negative ion mode has been well demonstrated for compounds that efficiently capture electrons.…”

Section: Resultsmentioning

confidence: 99%

“…Ionization occurs under vacuum conditions either by electron ionization or by chemical ionization [1]. On the other hand, ionization in LC/MS typically occurs at atmospheric pressure and the ions are swept into the vacuum system through differentially pumped regions separated by apertures or capillaries [4]. Ionization in atmospheric pressure LC/MS is by electrospray ionization (ESI) [5], corona discharge ionization [atmospheric pressure chemical ionization (APCI)] [6], photo ionization [7], or surface ionization [8].…”

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confidence: 99%

A combination atmospheric pressure LC/MS:GC/MS ion source: Advantages of dual AP-LC/MS:GC/MS instrumentation

McEwen

McKay

2005

J. Am. Soc. Mass Spectrom.

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Modification of commercial LC/MS instrumentation to allow both atmospheric pressure (AP) LC/MS and GC/MS is described. Advantages of this additional capability versus LC/MS alone include higher chromatographic resolution in the GC versus LC mode, greater peak capacity for complex mixture analysis, higher sensitivity for a variety of volatile compounds, and the ability to observe compounds of low polarity that are not readily observed in LC/MS. Advantages over conventional GC/MS include the ability to use higher carrier gas flow and shorter columns for passing less volatile materials through the gas chromatograph, selective ionization, and rapid switching between positive and negative ion modes. Other advantages include application of the enhanced capabilities of LC/MS instrumentation to GC/MS analyses such as cone voltage fragmentation, MS n , high mass resolution, and accurate mass measurement. Limitations of APGC/MS include the inability to observe saturated hydrocarbon and certain other highly nonpolar compounds and less odd-electron fragmentation for computer aided library searching. For some analyses, the limitation related to ionization of highly nonpolar compounds is advantageous, as is the simplified mass spectrum and easy molecular weight identification that results from less fragmentation observed in the AP ionization mode. (J Am Soc Mass Spectrom 2005, 16, 1730 -1738

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The coupling of gas and liquid chromatography with mass spectrometry

Abian

1999

J. Mass Spectrom.

112

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Atmospheric Pressure Ionization (API) Mass Spectrometry. Solvent-Mediated Ionization of Samples Introduced in Solution and in a Liquid Chromatograph Effluent Stream

Cited by 186 publications

References 0 publications

Characterization of direct-current atmospheric-pressure discharges useful for ambient desorption/ionization mass spectrometry

Characterization of direct-current atmospheric-pressure discharges useful for ambient desorption/ionization mass spectrometry

A combination atmospheric pressure LC/MS:GC/MS ion source: Advantages of dual AP-LC/MS:GC/MS instrumentation

The coupling of gas and liquid chromatography with mass spectrometry

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