Mechanism of Signal Suppression by Anionic Surfactants in Capillary Electrophoresis−Electrospray Ionization Mass Spectrometry

Rundlett, Kimber L.; Armstrong, Daniel W.

doi:10.1021/ac960472p

Cited by 172 publications

(146 citation statements)

References 48 publications

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“…In sharp contrast to these APCI results, the efficiency of ESI is known to decrease significantly in the presence of nonvolatile constituents such as sodium phosphate [2,8]. SDS, which is often employed as a pseudo-stationary phase in micellar electrokinetic chromatography (MEKC), is an even stronger ion suppressor in ESI [18,19]. However, the infusion experiments indicated that the addition of 20 mM SDS did not result in reduced signal intensities in APCI-MS. For hydrocortisone, SDS even caused a slight signal increase.…”

Section: Bge Compositionmentioning

confidence: 99%

Capillary electrophoresis-atmospheric pressure chemical ionization-mass spectrometry using an orthogonal interface: Set-up and system parameters

Hommerson

Khan

Jong

et al. 2009

J. Am. Soc. Mass Spectrom.

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The feasibility of atmospheric pressure chemical ionization (APCI) as an alternative ionization technique for capillary electrophoresis-mass spectrometry (CE-MS) was investigated using a grounded sheath-flow CE-MS sprayer and an orthogonal APCI source. Infusion experiments indicated that highest analyte signals were achieved when the sprayer tip was in close vicinity of the vaporizer entrance. The APCI-MS set-up enabled detection of basic, neutral, and acidic compounds, whereas apolar and ionic compounds could not be detected. In the positive ion mode, analytes could be detected in the entire transfer voltage range (0 -5 kV), whereas highest signal intensities were observed when the corona discharge current was between 1000 and 2000 nA. In the negative ion mode, the transfer voltage typically was 500 V and the optimum corona discharge current was 6000 nA. Analyte signals were raised with increasing nebulizing gas pressure, but the pressure was limited to 25 psi to avoid siphoning and current drops. Signal intensities appeared to be optimal and constant over a wide range of sheath liquid flow rate (5-25 L/min) and vaporizer temperature (200 -350°C). APCI-MS signals were unaffected by the composition of the background electrolyte (BGE), even when it contained sodium phosphate and sodium dodecyl sulfate (SDS). Consequently, BGE composition, sheath-liquid flow rate, and vaporizer temperature can be optimized with respect to the CE separation without affecting the APCI-MS response. The analysis of a mixture of basic compounds and a steroid using volatile and nonvolatile BGEs further demonstrates the feasibility of CE-APCI-MS. Detection limits (S/N ϭ 3) were 1.6 -10 M injected concentrations. (J Am Soc Mass

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Section: Bge Compositionmentioning

confidence: 99%

Capillary electrophoresis-atmospheric pressure chemical ionization-mass spectrometry using an orthogonal interface: Set-up and system parameters

Hommerson

Khan

Jong

et al. 2009

J. Am. Soc. Mass Spectrom.

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“…Indeed, common buffers used in CE-UV such as phosphate or borate which provide good peak shapes and thus high separation efficiency are nonvolatile and/or can contain modifiers such as CD, SDS, and so on. These additives are not suitable or even detrimental for on-line CE-ESI/MS since they may contaminate the MS ionization chamber and cause significant ion suppression [18,19]. Numerous solutions have been proposed to overcome these difficulties, such as the partial filling approach in chiral analysis [20], but they are not always well adapted or easy to carry out.…”

Section: Introductionmentioning

confidence: 99%

Coupling CE with atmospheric pressure photoionization MS for pharmaceutical basic compounds: Optimization of operating parameters

Schappler¹,

Guillarme²,

Prat³

et al. 2007

Electrophoresis

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The use of CE coupled with MS (CE-MS) has evolved as a useful tool to analyze charged species in small sample volumes. Because of its sensitivity, versatility and ease of implementation, the ESI interface is currently the method of choice to hyphenate CE to MS. An alternative can be the atmospheric pressure photoionization (APPI) source, however, numerous parameters must be optimized for its coupling to CE. After evaluation of the sheath liquid composition and the CE capillary outlet position, an experimental design methodology was assessed for optimizing other ionization source parameters, such as sheath liquid flow rate, drying gas flow rate and temperature, nebulizing gas pressure, vaporizer temperature, and capillary voltage. For this purpose, a fractional factorial design (FFD) was selected as a screening procedure to identify factors which significantly influence sensitivity and efficiency. A face-centered central composite design (CCD) was then used to predict and optimize sensitivity, taking into account the most relevant variables. Sensitivity was finally evaluated with the optimized conditions and height-to-noise ratios (H/N) around 10 were achieved for an injection of 200 ng/mL of each analyte.

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“…Furthermore, secondary structure elements and structural dynamics can also be studied by mass spectrometry in hydrogen/deuterium exchange experiments, in which the exchange kinetics of amide protons are measured (21-23), making ES mass spectrometry an attractive tool for studies of protein structure and organization. However, the study of detergent-solubilized proteins by ES mass spectrometry is challenging because of protein ion signal suppression due to the presence of excess detergent (24). Consequently, analysis of integral membrane proteins has usually relied on the removal of detergent prior to sample analysis by, for example, organic solvent extraction (25) or reversed-phase (26) or size-exclusion (27,28) chromatography.…”

mentioning

confidence: 99%

Observation of an Intact Noncovalent Homotrimer of Detergent-solubilized Rat Microsomal Glutathione Transferase-1 by Electrospray Mass Spectrometry

Lengqvist

Svensson

Evergren

et al. 2004

Journal of Biological Chemistry

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Microsomal glutathione transferase-1 (MGST1) is a membrane-bound enzyme involved in the detoxification of xenobiotics and the protection of cells against oxidative stress. The proposed active form of the enzyme is a noncovalently associated homotrimer that binds one substrate glutathione molecule/trimer. In this study, this complex has been directly observed by electrospray mass spectrometry analysis of active rat liver MGST1 reconstituted in a minimum amount of detergent. The measured mass of the homotrimer is 53 kDa, allowing for the mass of three MGST molecules in complex with one glutathione molecule. Collision-induced dissociation of the trimer complex resulted in the formation of monomer and homodimer ion species. Two distinct species of homodimer were observed, one unliganded and one identified as a homodimer⅐glutathione complex. Activation of the enzyme by N-ethylmaleimide through modification of Cys 49 (Svensson, R., Rinaldi, R., Swedmark, S., and Morgenstern, R. (2000) Biochemistry 39, 15144 -15149) was monitored by the observation of an appropriate increase in mass in both the denatured monomeric and native trimeric forms of MGST1. Together, the data correspond well with the proposed functional organization of MGST1. These results also represent the first example of direct electrospray mass spectrometry analysis of a detergent-solubilized multimeric membrane protein complex in its native state.Membrane proteins are estimated to constitute about onethird of the total proteome (1) and have important and diverse roles in biology, including functions as cell-surface receptors, ion channels, and transporters and in cell adhesion. However, because of the difficulty in producing crystals of detergentsolubilized proteins for x-ray crystallography, only ϳ1% of the unique protein structures so far solved at high resolution are of membrane proteins (2). Integral membrane proteins thus pose an important challenge in structural biology.Microsomal glutathione transferase-1 (MGST1) 1 is a member of the MAPEG (membrane-associated proteins in eicosanoid and glutathione metabolism) superfamily. At present, other mammalian members of the MAPEG family are two glutathione transferases/peroxidases (MGST2 and MGST3), 5-lipoxygenase-activating protein, leukotriene C 4 synthase, and microsomal prostaglandin E 2 synthase (the closest relative to MGST1) (3). MGST1 functions both as a glutathione transferase and as a peroxidase, thus potentially protecting cells from reactive compounds and oxidative stress (3, 4). The quaternary structure of MGST1 has previously been investigated by electron crystallography (5, 6), radiation inactivation (7), cross-linking (8), and hydrodynamic (9) studies and has been suggested to be a homotrimer both in the microsomal membrane and in the purified form. Electrospray (ES) mass spectrometry has shown that the enzyme is partly N-acetylated (10). Interestingly, equilibrium dialysis (11) and stopped-flow active-site titrations (12) have indicated that the MGST1 homotrimer binds only one molecule of ...

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Mechanism of Signal Suppression by Anionic Surfactants in Capillary Electrophoresis−Electrospray Ionization Mass Spectrometry

Cited by 172 publications

References 48 publications

Capillary electrophoresis-atmospheric pressure chemical ionization-mass spectrometry using an orthogonal interface: Set-up and system parameters

Capillary electrophoresis-atmospheric pressure chemical ionization-mass spectrometry using an orthogonal interface: Set-up and system parameters

Coupling CE with atmospheric pressure photoionization MS for pharmaceutical basic compounds: Optimization of operating parameters

Observation of an Intact Noncovalent Homotrimer of Detergent-solubilized Rat Microsomal Glutathione Transferase-1 by Electrospray Mass Spectrometry

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