Electrospray interface for liquid chromatographs and mass spectrometers

Whitehouse, Craig M.; Dreyer, Robert N.; Yamashita, Masamichi; Fenn, John B.

doi:10.1021/ac00280a023

Cited by 1,433 publications

(714 citation statements)

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“…1 Fenn et al further demonstrated the applications ESI in mass spectrometry (MS) techniques in the early 1980s 2,3 and received the Nobel prize in chemistry in 2002 due to this invention. ESI has become one of the most important and powerful ionization techniques for MS because of its effectiveness in detecting large biomolecules 4 and ease-ofuse for interfacing liquid-based separation techniques such as liquid chromatography (LC) 5,6 and capillary electrophoresis (CE). [7][8][9] A conventional ESI source typically employs flow rates in the range of 4-200 μL/min through a capillary that has 50-200 μm inner diameter (i.d.).…”

Section: Introductionmentioning

confidence: 99%

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Characterizing Electrospray Ionization Using Atmospheric Pressure Ion Mobility Spectrometry

2006

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Reduced flow-rate electrospray ionization has been proven to provide improved sensitivity, less background noise, and improved limits of detections for ESI-MS analysis. Miniaturizing the ESI source from conventional electrospray to micro-electrospray and further down to nanoelectrospray has resulted in higher and higher sensitivity. However, when effects of flow rate were investigated for atmospheric pressure ESI-IMS using a nanospray emitter, a striking opposite result was observed. The general tendency we observed in ESI-IMS was that higher flow rate offered higher ion signal intensity throughout a variety of conditions investigated. Thus further efforts were undertaken to rationalize these contradictory results. It is well accepted that decreased flow rate increases both ionization efficiency and transmission efficiency thus improves ion signal in ESI-MS. However, our study revealed that decreased flow rate results in decreased ion signal because ion transfer is constant no matter how flow rate changes in ESI-IMS. Since ion transfer is constant in atmospheric pressure ESI-IMS, ionization efficiency can be studied independently, which otherwise is not possible in ESI-MS where both ionization efficiency and transmission efficiency vary as conditions alter. In this report, we present a systematic study on signal intensity and ionization efficiency at various experimental conditions using ESI-IMS and demonstrated the ionization efficiency as a function of flow rate, analyte concentration, and solvent composition.

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Section: Introductionmentioning

confidence: 99%

“…[7][8][9] A conventional ESI source typically employs flow rates in the range of 4-200 μL/min through a capillary that has 50-200 μm inner diameter (i.d.). 5 A micro-electrospray source makes use of a tapered emitter with a small terminal orifice (usually < 20 μm i.d.) and much lower flow rates in the range of 0.1-1μL/min.…”

Section: Introductionmentioning

confidence: 99%

Characterizing Electrospray Ionization Using Atmospheric Pressure Ion Mobility Spectrometry

2006

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“…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]. Because ionization in GC/MS occurs under vacuum conditions and in LC/MS occurs at atmospheric pressure, the two separation methods require entirely different interfaces to the mass spectrometer and are thus usually performed on instruments dedicated to the particular chromatography method.…”

mentioning

confidence: 99%

“…In recent years, atmospheric pressure mass spectrometers have proliferated, primarily because of electrospray ionization and the ease of interfacing this atmospheric pressure ionization method to liquid chromatographs [5]. In addition, many of the mass spectrometers currently used for LC/MS have capability for MS n studies and/or accurate mass measurement, capabilities that are more rare for GC/MS instrumentation.…”

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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.

105

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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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“…This system is capable of subfemtomole nanoflow LC-MS sensitivity in both positive and negative ion mode across the solvent gradient. and electrospray ionization-mass spectrometry (ESI-MS) has evolved substantially since its initial implementation in the 1980s [1]. Traditional LC systems operated at solvent flow rates that were orders of magnitude higher (hundreds of L/min to mL/min) than those used for mass spectrometry (tens of L/ min), resulting in the need for solvent flow splitters [2].…”

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confidence: 99%

Stable gradient nanoflow LC-MS

Schneider¹,

Guo²,

Fell³

et al. 2005

J. Am. Soc. Mass Spectrom.

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This paper demonstrates improved nanoflow LC-MS performance on a QqTOF instrument with the incorporation of a heated nanoflow interface (particle discriminator) and a nebulizer assisted sprayer. It is shown that the nebulizer broadens the usable range of electrospray potentials, simplifying the tuning procedure, particularly for negative mode nanoflow gradients. The improved desolvation capability with the particle discriminator results in signal/noise improvements of approximately 3.5ϫ for negative ion mode samples prepared in predominantly acidified water as well as increased ion current stability. For nanoLC applications, the combined desolvation capabilities of a counter-current gas and heated laminar flow chamber provide reduced background, increased signal stability, reduced background drift, and improved protein sequence coverage when compared with data generated with only a counter-current gas for desolvation. This system is capable of subfemtomole nanoflow LC-MS sensitivity in both positive and negative ion mode across the solvent gradient. and electrospray ionization-mass spectrometry (ESI-MS) has evolved substantially since its initial implementation in the 1980s [1]. Traditional LC systems operated at solvent flow rates that were orders of magnitude higher (hundreds of L/min to mL/min) than those used for mass spectrometry (tens of L/ min), resulting in the need for solvent flow splitters [2]. Some of the subsequent improvements were focused on the use of nebulizer gases [3] and heating [4,5] for stabilization of the electrospray process to accommodate higher LC solvent flows.An alternate approach involves modification of the LC system to accommodate separations within the nanoflow regime [6,7]. Nanoflow LC-MS offers benefits in terms of sensitivity, solvent consumption, and sample consumption when compared with higher flow rate LC-MS, however, it can be much more difficult to operate. Nanoflow sprayers are typically fabricated from tapered fused silica capillary resulting in the need for some type of surface coating [8,9], inserted electrode [10,11], conductive union [6, 12, 13], or dialysis membrane [14] for application of the electrospray potential. Alternatively, sprayers can be fabricated from conductive materials, such as stainless steel, [15], however, tapered stainless steel sprayers are much more difficult to fabricate than fused silica sprayers. An additional benefit associated with fused silica sprayers is that the analytical column may be packed directly into the tapered sprayer, eliminating any post-column dead volume [16,17].A necessary but understated requirement for gradient elution in nanoLC-MS is an electrospray system that is capable of stable operation over a wide range of solvent compositions, particularly for samples containing both hydrophilic and hydrophobic components. Typical nanoflow electrospray systems display good stability for samples consisting of 20 to 100% organic solvent. However, stability can be an issue when running predominantly aqueous solvents because of the h...

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Electrospray interface for liquid chromatographs and mass spectrometers

Cited by 1,433 publications

References 28 publications

Characterizing Electrospray Ionization Using Atmospheric Pressure Ion Mobility Spectrometry

Characterizing Electrospray Ionization Using Atmospheric Pressure Ion Mobility Spectrometry

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

Stable gradient nanoflow LC-MS

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