JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2001
Lu Shan
Abstract Synthetic nylon-6 single molecular mass oligomers were studied by matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry. These oligomers, considered as model compounds for the study of nylon-6 polymers, gave good mass spectrometric results using both MALDI and ESI. In spite of the gentle nature of both techniques, the MALDI and ESI spectra showed evidence of end-group cleavage from the oligomer chains. MALDI-MS was found to give similar fragmentation patterns for all of the oligomer samples. An increase in doubly charged ion signals with increasing oligomer mass was observed in the ESI mass spectra, as was end-group fragmentation. Signals from oligomer clusters were observed in ESI-MS for the dimer, tetramer and hexamer, most likely due to non-covalent bonding among the low-mass oligomer molecules. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Electrospray: From ions in solution to ions in the gas phase, what we know now

MASS SPECTROMETRY REVIEWS, Issue 6 2009
Paul Kebarle
Abstract There is an advantage for users of electrospray and nanospray mass spectrometry to have an understanding of the processes involved in the conversion of the ions present in the solution to ions in the gas phase. The following processes are considered: Creation of charge droplets at the capillary tip; Electrical potentials required and possibility of gas discharges; Evolution of charged droplets, due to solvent evaporation and Coulomb explosions, to very small droplets that are the precursors of the gas phase ions; Production of gas phase ions from these droplets via the Ion Evaporation and Charge residue models; Analytical uses of ESIMS of small ions, qualitative and quantitative analysis; Effects of the ESI mechanism on the analysis of proteins and protein complexes; Determination of stability constants of protein complexes; Role of additives such as ammonium acetate on the observed mass spectra. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:898,917, 2009 [source]

Electrospray ionization from a gap with adjustable width

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2006
Patrik Ek
In this paper, we present a new concept for electrospray ionization mass spectrometry, where the sample is applied in a gap which is formed between the edges of two triangular-shaped tips. The size of the spray orifice can be changed by varying the gap width. The tips were fabricated from polyethylene terephthalate film with a thickness of 36,µm. To improve the wetting of the gap and sample confinement, the edges of the tips forming the gap were hydrophilized by means of silicon dioxide deposition. Electrospray was performed with gap widths between 1 and 36,µm and flow rates down to 75,nL/min. The gap width could be adjusted in situ during the mass spectrometry experiments and nozzle clogging could be managed by simply widening the gap. Using angiotensin I as analyte, the signal-to-noise ratio increased as the gap width was decreased, and a shift towards higher charge states was observed. The detection limit for angiotensin I was in the low nM range. Copyright © 2006 John Wiley & Sons, Ltd. [source]

CEC-ESI ion trap MS of multiple drugs of abuse

ELECTROPHORESIS, Issue 7 2010
Zeineb Aturki
Abstract This article describes a method for the separation and determination of nine drugs of abuse in human urine, including amphetamines, cocaine, codeine, heroin and morphine. This method was based on SPE on a strong cation exchange cartridge followed by CEC-MS. The CEC experiments were performed in fused silica capillaries (100,,m×30,cm) packed with a 3,,m cyano derivatized silica stationary phase. A laboratory-made liquid junction interface was used for CEC-MS coupling. The outlet capillary column was connected with an emitter tip that was positioned in front of the MS orifice. A stable electrospray was produced at nanoliter per minute flow rates applying a hydrostatic pressure (few kPa) to the interface. The coupling of packed CEC columns with mass spectrometer as detector, using a liquid junction interface, provided several advantages such as better sensitivity, low dead volume and independent control of the conditions used for CEC separation and ESI analysis. For this purpose, preliminary experiments were carried out in CEC-UV to optimize the proper mobile phase for CEC analysis. Good separation efficiency was achieved for almost all compounds, using a mixture containing ACN and 25,mM ammonium formate buffer at pH 3 (30:70, v/v), as mobile phase and applying a voltage of 12,kV. ESI ion-trap MS detection was performed in the positive ionization mode. A spray liquid, composed by methanol,water (80:20, v/v) and 1% formic acid, was delivered at a nano-flow rate of ,200,nL/min. Under optimized CEC-ESI-MS conditions, separation of the investigated drugs was performed within 13,min. CEC-MS and CEC-MS2 spectra were obtained by providing the unambiguous confirmation of these drugs in urine samples. Method precision was determined with RSDs values ,3.3% for retention times and ,16.3% for peak areas in both intra-day and day-to-day experiments. LODs were established between 0.78 and 3.12,ng/mL for all compounds. Linearity was satisfactory in the concentration range of interest for all compounds (r2,0.995). The developed CEC-MS method was then applied to the analysis of drugs of abuse in spiked urine samples, obtaining recovery data in the range 80,95%. [source]

Identification and separation of DNA-hybridized nanocolloids by Taylor cone harmonics

ELECTROPHORESIS, Issue 18 2009
Xinguang Cheng
Abstract A rapid (minutes) electrospray bead-based DNA hybridization detection technique is developed by spraying a mixture of hybridized and unhybridized silica nanocolloids. With proper far-field control by external electrodes, the trajectory of the ejected nanobeads from the electrospray is governed by specific harmonics of the Laplace equation, which select discrete polar angles along well-separated field maxima near the conducting Taylor cone. Due to Rayleigh fission and evaporation, beads of different size acquire different total charge after ejection and suffer different normal electrophoretic displacement such that they are ejected along well-separated field maxima and are deposited in distinct rings on an intersecting plane. As the hybridized DNA is of the same dimension as that of the nanocolloid, the nanocolloids are hence easily differentiated from the unhybridized ones. This technique is highly specific as the high shear stress in the microjet shears away any non-specifically bound DNA from the nanocolloid surface. [source]

Glycoform characterization of erythropoietin combining glycan and intact protein analysis by capillary electrophoresis , electrospray , time-of-flight mass spectrometry

ELECTROPHORESIS, Issue 13 2006
Elvira Balaguer
Abstract Glycosylation of recombinant human erythropoietin (rHuEPO) is a post-translational process that alters biological activity, solubility and lifetime of the glycoprotein in blood, and strongly depends on the type of cell and the cell culture conditions. A fast and simple method providing extensive carbohydrate information about the glycans present in rHuEPO and other glycoproteins is needed in order to improve current methods in drug development or product quality control. Here, an improved method for intact rHuEPO glycoform characterization by CZE-ESI-TOF MS has been developed using a novel capillary coating and compared to a previous study. Both methods allow a fast separation in combination with accurate mass characterization of the single protein isoforms. The novel dynamic coating provides a separation at an EOF close to zero, enabling better separation. This results in an improved mass spectrometric resolution and the detection of minor isoforms. In order to assign an unequivocal carbohydrate composition to every intact glycoform, a CZE-ESI-MS separation method for enzymatically released underivatized N -glycans has been developed. The TOF,MS allows the correct identification of the glycans due to its high mass accuracy and resolution. Therefore, glycan modifications such as acetylation, oxidation, sulfation and even the exchange of OH by NH2 are successfully characterized. Information of the protein-backbone molecular mass has been combined with results from peptide analysis (revealing information about O -glycosylation) and from the glycan analysis, including the detection of as yet undescribed glycans containing four antennae and five sialic acids. This allows an unequivocal assignment of an overall glycosylation composition to the molecular masses obtained for the intact rHuEPO glycoforms. [source]

Electrokinetic-driven microfluidic system in poly(dimethylsiloxane) for mass spectrometry detection integrating sample injection, capillary electrophoresis, and electrospray emitter on-chip

ELECTROPHORESIS, Issue 24 2005
Sara Thorslund
Abstract A novel microsystem device in poly(dimethylsiloxane) (PDMS) for MS detection is presented. The microchip integrates sample injection, capillary electrophoretic separation, and electrospray emitter in a single substrate, and all modules are fabricated in the PDMS bulk material. The injection and separation flow is driven electrokinetically and the total amount of external equipment needed consists of a three-channel high-voltage power supply. The instant switching between sample injection and separation is performed through a series of low-cost relays, limiting the separation field strength to a maximum of 270,V/cm. We show that this set-up is sufficient to accomplish electrospray MS analysis and, to a moderate extent, microchip separation of standard peptides. A new method of instant in-channel oxidation makes it possible to overcome the problem of irreversibly bonded PDMS channels that have recovered their hydrophobic properties over time. The fast method turns the channel surfaces hydrophilic and less prone to nonspecific analyte adsorption, yielding better separation efficiencies and higher apparent peptide mobilities. [source]

Fabrication of enclosed SU-8 tips for electrospray ionization-mass spectrometry

ELECTROPHORESIS, Issue 24 2005
Santeri Tuomikoski Dr.
Abstract We describe a novel electrospray tip design for MS which is fabricated completely out of SU-8 photoepoxy. A three-layer SU-8 fabrication process provides fully enclosed channels and tips. The tip shape and alignment of all SU-8 layers is done lithographically and is therefore very accurate. Fabrication process enables easy integration of additional fluidic functions on the same chip. Separation channels can be made with exactly the same process. Fluidic inlets are made in SU-8 during the fabrication process and no drilling or other postprocessing is needed. Channels have been fabricated and tested in the size range of 10,,m×10,,m,50,,m×200,,m. Mass spectrometric performance of the tips has been demonstrated with both pressure-driven flow and EOF. SU-8 microtips have been shown to produce stable electrospray with EOF in a timescale of tens of minutes. With pressure driven flow stable spray is maintained for hours. Taylor cone was shown to be small in volume and well defined even with the largest channel cross section. The spray was also shown to be well directed with our tip design. [source]

Synthesis and Properties of Organometallic PtII and PtIV Complexes with Acyclic Selenoether and Telluroether Ligands and Selenoether Macrocycles

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2006
William Levason
Abstract The first series of planar dimethyl(selenoether)PtII complexes, [PtMe2L] [L = MeSe(CH2)nSeMe (n = 2 or 3), o -C6H4(CH2SeMe)2, [8]aneSe2 (1,5-diselenacyclooctane), or [16]aneSe4 (1,5,9,13-tetraselenacyclohexadecane)], have been obtained by treatment of [PtMe2(SMe2)2] with L in Et2O solution and characterised by VT 1H, 13C{1H}, 77Se{1H} and 195Pt{1H} NMR spectroscopy, electrospray MS and microanalysis. The corresponding dimethyl(telluroether)PtII complexes do not form under similar reaction conditions. The distorted octahedral [PtMe3I(L)] [L = o -C6H4(CH2SeMe)2, [8]aneSe2, [16]aneSe4 or MeC(CH2SeMe)3] form as stable complexes in good yield from reaction of PtMe3I with L in refluxing CHCl3 and have been characterised similarly. These all show bidentate selenoether coordination, with fast pyramidal inversion occurring at room temperature. The distorted octahedral coordination environment at PtIV is also confirmed from a crystal structure of [PtMe3I{o -C6H4(CH2SeMe)2}]. Rare examples of (telluroether)PtIV complexes, [PtMe3I{o -C6H4(CH2TeMe)2}] and the dinuclear [Me3Pt(,2 -I)2(,2 -MeTeCH2TeMe)PtMe3], have also been prepared and characterised similarly (and also by 125Te{1H} NMR spectroscopy). The [8]aneSe2 and [16]aneSe4 species are the first examples of alkyl PtII or PtIV complexes with (macro)cyclic selenoether coordination. Halide abstraction (TlPF6) from [PtMe3I(,2 -[16]aneSe4)] affords [PtMe3(,3 -[16]aneSe4)]PF6; a rare example of a cationic PtIV selenoether. The (diselenoether)PtII complexes undergo oxidative addition of MeI to yield the corresponding PtIV species [PtMe3I(diselenoether)]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Fabrication of Density Gradients of Biodegradable Polymer Microparticles and Their Use in Guiding Neurite Outgrowth

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
Xiaoran Li
Abstract A new method for generating both continuous and discrete density gradients in microparticles of biodegradable polymers via an electrospray technique is reported. The gradients are generated by spatially varying the deposition time of electrosprayed microparticles. The substrate coated with a density gradient of microparticles has varying surface roughness, offering a unique system for studying the effect of physical cues on neurite outgrowth from dorsal root ganglia. An optimal surface roughness for promoting neuron adhesion and neurite extension in vitro is obtained. Furthermore, this capability of approach is extended to generate a gradient of fluorescein isothiocyanate labeled bovine serum albumin by encapsulating it in the polymer microparticles in situ during electrospray. Taken together, this new class of substrates with gradients of microparticle density can potentially be used in various biomedical applications such as neural tissue engineering. [source]

Emulsion as a Means of Controlling Electrospinning of Polymers

ADVANCED MATERIALS, Issue 18 2009
Jay C. Sy
A generalized approach to attain spinnability in polymer solutions in electrospinning using emulsions is described. By using emulsions, low-molecular weight (MW) polymer solutions that tend to electrospray can be spun into nanofibers. Additionally, control over fiber properties independent of polymer solution viscosity and MW is achieved, with an order of magnitude reduction in fiber diameter upon emulsification. Nanofibrous sheets obtained demonstrate excellent cellular biocompatibility and are suitable for tissue contacting applications. [source]

Electrospray-Assisted Fabrication of Uniform Photonic Balls,

ADVANCED MATERIALS, Issue 7 2004
H. Moon
Photonic balls have been fabricated (see Figure) by field-enhanced electrospray of an aqueous colloidal suspension. The polystyrene (PS) beads inside the suspension droplets self-organize into opaline balls while the solvent evaporates. The opaline balls are used as templates for inverse opaline photonic balls, and both types exhibit varying reflection colors depending on the diameter of the beads and the reflective index contrast. [source]

Direct analysis of lipids in mouse brain using electrospray droplet impact/SIMS

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2010
Daiki Asakawa
Abstract Electrospray droplet impact (EDI)/secondary ion mass spectrometry (SIMS) is a new desorption/ionization technique for mass spectrometry in which highly charged water clusters produced from the atmospheric-pressure electrospray are accelerated in vacuum by 10 kV and impact the sample deposited on the metal substrate. EDI/SIMS was shown to enhance intact molecular ion formation dramatically compared to conventional SIMS. EDI/SIMS has been successfully applied to the analysis of mouse brain without any sample preparation. Five types of lipids, i.e. phosphatidylcholine (PC), phosphatidylserine, phosphatidylinositol (PI), galactocerebroside (GC) and sulfatide (ST), were readily detected from mouse brain section. In addition, by EDI/SIMS, six different regions of the mouse brain (cerebral cortex, corpus callosum, striatum, medulla oblongata, cerebellar cortex and cerebellar medulla) were examined. While GCs and STs were found to be rich in white matter, PIs were rich in gray matter. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Quantitative analysis of EO9 (apaziquone) and its metabolite EO5a in human plasma by high-performance liquid chromatography under basic conditions coupled to electrospray tandem mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2006
Liia D. Vainchtein
A sensitive and specific LC-MS/MS assay for the quantitative determination of EO9 and its metabolite EO5a is presented. A 200-µl human plasma aliquot was spiked with a mixture of deuterated internal standards EO9- d3 and EO5a- d4 and extracted with 1.25 ml ethyl acetate. Dried extracts were reconstituted in 0.1 M ammonium acetate,methanol (7 : 3, v/v) and 25 µl-volumes were injected into the HPLC system. Separation was achieved on a 150 × 2.1 mm C18 column using an alkaline eluent (1 mM ammonium hydroxide,methanol (gradient system)). Detection was performed by positive ion electrospray followed by tandem mass spectrometry. The assay quantifies a range from 5 to 2500 ng/ml for EO9 and from 10 to 2500 ng/ml EO5a using 200 µl of human plasma samples. Validation results demonstrate that EO9 and EO5a concentrations can be accurately and precisely quantified in human plasma. This assay will be used to support clinical pharmacologic studies with EO9. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Preparative separation of a multicomponent peptide mixture by mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006
Xinli Yang
Abstract We report on the first multiplex preparative separation by mass spectrometry of bio-organic molecules in the 200,350 Da mass range that is typical for synthetic drugs. A five-component mixture consisting of two di- and three tripeptides has been separated by mass using a specially designed mass spectrometer. The instrument for preparative separations consists of an electrospray ionization (ESI) source, ion transfer optics, an electrostatic sector, and an inhomogeneous-field magnetic mass analyzer that achieves linear mass dispersion of ion beams. Protonated peptides produced by electrospray were separated, nondestructively landed on a 16-channel array of dry collector plates, and reconstituted in solution. The preparation procedures and the instrumental conditions have been optimized to maximize the ion currents. The significant features of the special mass spectrometer are high ion currents and simultaneous separation and collection of mixture components. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Effect of buffer cations and of H3O+ on the charge states of native proteins.

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2003
Significance to determinations of stability constants of protein complexes
Abstract The progressive reduction of charge in charge states of non-denatured proteins (lysozyme, ubiquitin, and cytochrome c), observed with nanospray in the positive ion mode, when the buffer salt ammonium acetate is replaced by ethylammonium acetates (EtNH3Ac, Et2NH2Ac and Et3NHAc) is rationalized on the basis of the charge residue model (CRM). The charge states of the multiply protonated protein are shown to be controlled by the increasing gas-phase basicities, GB(B), of the bases(B) NH3, EtNH2, Et2NH and Et3N. Charge states derived from evaluated apparent gas-phase basicities GBapp of the basic side-chains of the protein and the known GB(B) of the above bases are found to be in agreement with the experimentally observed charge states. This is a requirement of the CRM, because in this model the small positive ions (the buffer cations in the present case) at the surface of the electrospray droplets are the excess ions that provide the charge of the final small droplet that contains the protein molecule and on evaporation of the solvent transfer the charge to the protein. The observed charge states in the absence of buffer salts, i.e. pure water, are attributed to excess H3O+ ions produced by the electrolysis process that attends electrospray. A proposed extended mechanism provides predictions of factors that determine the sensitivity for detection of the multiply protonated proteins. Consideration of restraints imposed by the CRM lead to some simple predictions for conditions that should be present to obtain accurate determinations by electrospray and nanospray of stability constants for the protein,complex equilibrium in aqueous solution. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Attachment of neutrals during tandem mass spectrometry of sulfonic acid dyes andintermediates in an ion trap

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2002
Adrian Weisz
Abstract Several positional isomers of 2-(2-quinolinyl)-1H -indene-1,3(2H)-dione mono- and disulfonic acids prepared as reference materials for development of analytical methods involved in FDA certification of D&C Yellow No. 10 (Quinoline Yellow) were found consistently to show [MH + 14]+ ions when their electrospray- or atmospheric pressure chemical ionization-prepared MH+ ions were subjected to collisional activation. The source of these ions was found to be the methanol used as solvent in these procedures which combined with their [MH , H2O]+ ions under chemical ionization conditions. The reaction was found to be sensitive to their isomeric and chemical structures and other examples of this process are reviewed. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Validated assay for quantification of oxcarbazepine and its active dihydro metabolite 10-hydroxycarbazepine in plasma by atmospheric pressure chemical ionization liquid chromatography/mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2002
Hans H. Maurer
Abstract Oxcarbazepine (OX), a new antiepileptic, may lead to unwanted side-effects or even life-threatening intoxications after overdose. Therefore, a validated liquid chromatographic/mass spectrometric (LC/MS) assay was developed for the quantification of OX and its pharmacologically active dihydro metabolite (dihydrooxcarbazepine, DOX, often named 10-hydroxycarbazepine). OX and DOX were extracted from plasma by the authors' standard liquid/liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. The compounds were quantified in the selected-ion monitoring mode using atmospheric pressure chemical ionization electrospray LC/MS. The assay was fully validated. It was found to be selective. The calibration curves were linear from 0.1 to 50 mg l,1 for OX and DOX. Limits of quantification were 0.1 mg l,1 for OX and DOX. The absolute recoveries were between 60 and 86%. The accuracy and precision data were within the required limits. The analytes in frozen plasma samples were stable for at least 1 month. The method was successfully applied to several authentic plasma samples from patients treated or intoxicated with OX. The measured therapeutic plasma levels ranged from 1 to 2 mg l,1 for OX and from 10 to 40 mg l,1 for DOX. The validated LC/MS assay proved to be appropriate for quantification of OX and DOX in plasma for clinical toxicology and therapeutic drug monitoring purposes. The assay is part of a general analysis procedure for the isolation, separation and quantification of various drugs and for their full-scan screening and identification. Copyright © 2002 John Wiley & Sons, Ltd. [source]

A novel tandem quadrupole mass spectrometer allowing gaseous collisional activation and surface induced dissociation

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2001
Shabaz Mohammed
Abstract A novel tandem quadrupole mass spectrometer is described that enables gaseous collision-induced dissociation (CID) and surface-induced dissociation (SID) experiments. The instrument consists of a commercially available triple quadrupole mass spectrometer connected to an SID region and an additional, orthogonal quadrupole mass analyser. The performance of the instrument was evaluated using leucine-enkephalin, allowing a comparison between CID and SID, and with previous reports of other SID instruments. The reproducibility of SID data was assessed by replicate determinations of the collision energy required for 50% dissociation of leucine-enkephalin; excellent precision was observed (standard deviation of 0.6 eV) though, unexpectedly, the reproducibility of the equivalent figure for CID was superior. Several peptides were analysed using SID in conjunction with liquid secondary-ion mass spectrometry or electrospray; a comparison of the fragmentation of singly protonated peptide ions and the further dissociation of y-type fragments was consistent with the equivalence of the latter fragments to protonated peptides. Few product ions attributable to high-energy cleavages of amino acid side-chains were observed. The SID properties were investigated of a series of peptides differing only in the derivatization of a cysteine residue; similar decomposition efficiencies were observed for all except the cysteic acid analogue, which demonstrated significantly more facile fragmentation. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Characterization via liquid chromatography coupled to diode array detector and tandem mass spectrometry of supercritical fluid antioxidant extracts of Spirulina platensis microalga

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2005
Jose A. Mendiola
Abstract Spirulina platensis microalga has been extracted on a pilot scale plant using supercritical fluid extraction (SFE) under various extraction conditions. The extraction yield and the antioxidant activity of the extracts were evaluated in order to select those extracts with both the highest antioxidant capacity and a good extraction yield. These extracts were characterized using LC coupled to diode array detection (DAD) and LC coupled to mass spectrometry (MS) with two different interfaces, atmospheric pressure chemical ionization (APCI) and electrospray (ESI) which allowed us to perform tandem MS by using an ion trap analyzer. The best extraction conditions were as follows: CO2 with 10% of modifier (ethanol) as extraction solvent, 55°C (extraction temperature) and 220 bar (extraction pressure). Fractionation was achieved by cascade depressurization providing two extracts with different activity and chemical composition. Several compounds have been identified in the extracts, corresponding to different carotenoids previously identified in Spirulina platensis microalga along with chlorophyll a and some degradation products. Also, the structure of some phenolic compounds could be tentatively identified. The antioxidant activity of the extracts could be attributed to some of the above mentioned compounds. [source]

The ion funnel: Theory, implementations, and applications

MASS SPECTROMETRY REVIEWS, Issue 2 2010
Ryan T. Kelly
Abstract The electrodynamic ion funnel has enabled the manipulation and focusing of ions in a pressure regime (0.1,30 Torr) that has challenged traditional approaches, and provided the basis for much greater mass spectrometer ion transmission efficiencies. The initial ion funnel implementations aimed to efficiently capture ions in the expanding gas jet of an electrospray ionization interface and radially focus them for efficient transfer through a conductance limiting orifice. We review the improvements in fundamental understanding of ion motion in ion funnels, the evolution in its implementations that have brought the ion funnel to its current state of refinement, as well as applications of the ion funnel for purposes such as ion trapping, ion cooling, low pressure electrospray, and ion mobility spectrometry. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:294,312, 2010 [source]

Electrospray: From ions in solution to ions in the gas phase, what we know now

Matrix effects in quantitative pesticide analysis using liquid chromatography,mass spectrometry

MASS SPECTROMETRY REVIEWS, Issue 6 2006
W.M.A. Niessen
Abstract Combined liquid chromatography,mass spectrometry using electrospray or atmospheric-pressure chemical ionization has become an important tool in the quantitative analysis of pesticide residues in various matrices in relation to environmental analysis, food safety, and biological exposure monitoring. One of the major problems in the quantitative analysis using LC,MS is that compound and matrix-dependent response suppression or enhancement may occur, the so-called matrix effect. This article reviews issues related to matrix effects, focusing on quantitative pesticide analysis, but also paying attention to expertise with respect to matrix effects acquired in other application areas of LC,MS, especially quantitative bioanalysis in the course of drug development. © 2006 Wiley Periodicals, Inc. [source]

Mass spectrometry in bioinorganic analytical chemistry

MASS SPECTROMETRY REVIEWS, Issue 2 2006
Ryszard
Abstract A considerable momentum has recently been gained by in vitro and in vivo studies of interactions of trace elements in biomolecules due to advances in inductively coupled plasma mass spectrometry (ICP MS) used as a detector in chromatography and capillary and planar electrophoresis. The multi-isotopic (including non-metals such as S, P, or Se) detection capability, high sensitivity, tolerance to matrix, and large linearity range regardless of the chemical environment of an analyte make ICP MS a valuable complementary technique to electrospray MS and MALDI MS. This review covers different facets of the recent progress in metal speciation in biochemistry, including probing in vitro interactions between metals and biomolecules, detection, determination, and structural characterization of heteroatom-containing molecules in biological tissues, and protein monitoring and quantification via a heteroelement (S, Se, or P) signal. The application areas include environmental chemistry, plant and animal biochemistry, nutrition, and medicine. © 2005 Wiley Periodicals, Inc. Mass Spec Rev 25:255,289, 2006 [source]

Activation of large lons in FT-ICR mass spectrometry

MASS SPECTROMETRY REVIEWS, Issue 2 2005
Julia Laskin
Abstract The advent of soft ionization techniques, notably electrospray and laser desorption ionization methods, has enabled the extension of mass spectrometric methods to large molecules and molecular complexes. This both greatly extends the applications of mass spectrometry and makes the activation and dissociation of complex ions an integral part of these applications. This review emphasizes the most promising methods for activation and dissociation of complex ions and presents this discussion in the context of general knowledge of reaction kinetics and dynamics largely established for small ions. We then introduce the characteristic differences associated with the higher number of internal degrees of freedom and high density of states associated with molecular complexity. This is reflected primarily in the kinetics of unimolecular dissociation of complex ions, particularly their slow decay and the higher energy content required to induce decomposition,the kinetic shift (KS). The longer trapping time of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) significantly reduces the KS, which presents several advantages over other methods for the investigation of dissociation of complex molecules. After discussing general principles of reaction dynamics related to collisional activation of ions, we describe conventional ways to achieve single- and multiple-collision activation in FT-ICR MS. Sustained off-resonance irradiation (SORI),the simplest and most robust means of introducing the multiple collision activation process,is discussed in greatest detail. Details of implementation of this technique, required control of experimental parameters, limitations, and examples of very successful application of SORI-CID are described. The advantages of high mass resolving power and the ability to carry out several stages of mass selection and activation intrinsic to FT-ICR MS are demonstrated in several examples. Photodissociation of ions from small molecules can be effected using IR or UV/vis lasers and generally requires tuning lasers to specific wavelengths and/or utilizing high flux, multiphoton excitation to match energy levels in the ion. Photodissociation of complex ions is much easier to accomplish from the basic physics perspective. The quasi-continuum of vibrational states at room temperature makes it very easy to pump relatively large amounts of energy into complex ions and infrared multiphoton dissociation (IRMPD) is a powerful technique for characterizing large ions, particularly biologically relevant molecules. Since both SORI-CID and IRMPD are slow activation methods they have many common characteristics. They are also distinctly different because SORI-CID is intrinsically selective (only ions that have a cyclotron frequency close to the frequency of the excitation field are excited), whereas IRMPD is not (all ions that reside on the optical path of the laser are excited). There are advantages and disadvantages to each technique and in many applications they complement each other. In contrast with these slow activation methods, the less widely appreciated activation method of surface induced dissociation (SID) appears to offer unique advantages because excitation in SID occurs on a sub-picosecond time scale, instantaneously relative to the observation time of any mass spectrometer. Internal energy deposition is quite efficient and readily adjusted by altering the kinetic energy of the impacting ion. The shattering transition,instantaneous decomposition of the ion on the surface,observed at high collision energies enables access to dissociation channels that are not accessible using SORI-CID or IRMPD. Finally, we discuss some approaches for tailoring the surface to achieve particular aims in SID. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:135,167, 2005 [source]

The role of electron capture dissociation in biomolecular analysis

MASS SPECTROMETRY REVIEWS, Issue 2 2005
Helen J. Cooper
Abstract The introduction of electron capture dissociation (ECD) to electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) constitutes a significant advance in the structural analysis of biomolecules. The fundamental features and benefits of ECD are discussed in this review. ECD is currently unique to FT-ICR MS and the fundamentals of that technique are outlined. The advantages and complementarity of ECD in relation to other tandem mass spectrometry (MS/MS) techniques, such as infrared multiphoton dissociation (IRMPD) and sustained off-resonance collision-induced dissociation (SORI-CID), are discussed. The instrumental considerations associated with implementation of ECD, including activated ion techniques and coupling to on-line separation techniques, are covered, as are the allied processes electronic excitation dissociation (EED), electron detachment dissociation (EDD), and hot electron capture (HECD). A major theme of this review is the role of ECD in proteomics, particularly for characterization of post-translational modifications (phosphorylation, glycosylation, carboxyglutamic acid, sulfation, acylation, and methionine oxidation) and the top-down approach to protein identification. The application of ECD to the analysis of polymers, peptide nucleic acids, and oligonucleotides is also discussed. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:201,222, 2005 [source]

Oxidation of specific methionine and tryptophan residues of apolipoprotein A-I in hepatocarcinogenesis

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 18 2005
Jokin Fernández-Irigoyen
Abstract Hepatocellular carcinoma (HCC) is the fifth most common neoplasm with more than 500,000 new cases diagnosed yearly. Although major risk factors of HCC are currently known, the identification of biological targets leading to an early diagnosis of the disease is considered one of the priorities of clinical hepatology. In this work we have used a proteomic approach to identify markers of hepatocarcinogenesis in the serum of a knockout mice deficient in hepatic AdoMet synthesis (MAT1A,/,), as well as in patients with HCC. Three isoforms of apolipoprotein A-I (Apo A-I) with different pI were identified in murine serum. Isoform 1 is up-regulated in the serum of MAT1A,/, mice much earlier than any histological manifestation of liver disease. Further characterization of the differential isoform by electrospray MS/MS revealed specific oxidation of methionine 85 and 216 to methionine sulfoxide while the sequence of the analogous peptides on isoforms 2 and 3 showed the nonoxidized methionine residues. Enrichment of an acidic isoform of Apo A-I was also assessed in the serum of hepatitis B virus patients who developed HCC. Specific oxidation of methionine 112 to methionine sulfoxide and tryptophans 50 and 108 to formylkinurenine were identified selectively in the up-regulated isoform. Although it is not clear at present whether the occurrence of these modifications has a causal role or simply reflects secondary epiphenomena, this selectively oxidized Apo A-I isoform may be considered as a pathological hallmark that may help to the understanding of the molecular pathogenesis of HCC. [source]

Comprehensive characterization of marine dissolved organic matter by Fourier transform ion cyclotron resonance mass spectrometry with electrospray and atmospheric pressure photoionization

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2010
Juliana D'Andrilli
We compare the ultrahigh resolution 9.4,T Fourier transform ion cyclotron resonance (FT-ICR) mass spectra of marine dissolved organic matter (DOM) isolated from two sites in the Weddell Sea (Antarctica) obtained by complementary electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Ions produced by APPI extend to higher carbon unsaturation than those produced by ESI, indicated by higher double-bond equivalents (rings plus double bonds) minus oxygen (DBE-O) values, whereas ESI-generated ions are more oxygenated. Moreover, many sulfur-containing compounds were efficiently ionized by ESI but not detected by APPI. Because the mass spectra obtained by ESI and APPI are significantly different, both are necessary to obtain a more complete description of the molecular composition of marine DOM. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Non-disturbing characterization of natural organic matter (NOM) contained in clay rock pore water by mass spectrometry using electrospray and atmospheric pressure chemical ionization modes

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2010
Sandrine Huclier-Markai
We have investigated the composition of the mobile natural organic matter (NOM) present in Callovo-Oxfodian pore water using electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and emission-excitation matrix (EEM) spectroscopy. The generation of knowledge of the composition, structure and size of mobile NOM is necessary if one wants to understand the interactions of these compounds with heavy metals/radionuclides, in the context of environmental studies, and particularly how the mobility of these trace elements is affected by mobile NOM. The proposed methodology is very sensitive in unambiguously identifying the in situ composition of dissolved NOM in water even at very low NOM concentration, due to innovative non-disturbing water sampling and ionization (ESI/APCI-MS) techniques. It was possible to analyze a quite exhaustive inventory of the small organic compounds of clay pore water without proceeding to any chemical treatment at naturally occurring concentration levels. The structural features observed were mainly acidic compounds and fatty acids as well as aldehydes and amino acids. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Electrospray ionization and atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry of antioxidants applied in lubricants,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009
Alexander Kassler
The aim of this study was to investigate the utility of ion trap mass spectrometry (ITMS) in combination with the two desorption/ionization methods, electrospray (ESI) and atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI), for the detection of antioxidants which are applied in lubricants. These experiments should form the base for future investigations of antioxidants in tribologically formed thin layers on the surface of frictional systems. Seventeen different antioxidants were selected out of the group of hindered phenolic and aromatic aminic compounds. Practically all antioxidants could be characterized by positive ion ESI- and AP-MALDI-ITMS, forming various types/species of molecular ions (e.g. [M]+., [M+H]+, [M+Na]+ or [M,2H+H]+). A few compounds could be analyzed by negative ion ESI-MS, too, but none by negative ion AP-MALDI-MS. The influence of target materials in AP-MALDI-MS (gold- and titanium nitride (TiN)-covered stainless steel, micro-diamond-covered hard metal, hand-polished and sand-blasted stainless steel targets) with respect to the molecular ion intensity and type of molecular ion of two selected antioxidants was evaluated. The surface properties are of particular interest because in friction tests different materials with different surface characteristics are used. However, the MS results indicate that optimal target surfaces have to be found for individual antioxidants in AP-MALDI-MS but in general smooth surfaces were superior to rough surfaces. Finally the gold-covered stainless steel MALDI target provided the best mass spectra and was selected for all the antioxidants investigated. Copyright © 2009 John Wiley & Sons, Ltd. [source]