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At least 19 recordsLinked to original sources
PubMed2003

Separation and quantitation of the stereoisomers of ephedra alkaloids in natural health products using flow injection-electrospray ionization-high field asymmetric waveform ion mobility spectrometry-mass spectrometry.

A method is described for the determination of ephedrine (E) and pseudoephedrine (PE) and their metabolites norephedrine (NE), norpseudoephedrine (NPE), methylephedrine (ME), and methylpseudoephedrine (MPE) alkaloids in natural health products by flow injection-electrospray ionization-high field asymmetric waveform ion mobility spectrometry-mass spectrometry (FI-ESI-FAIMS-MS). The determination of the six alkaloids requires the separation of diastereomic pairs of E-PE, NE-NPE, and ME-MPE. FAIMS was able to resolve/separate these isomeric pairs based on their gas-phase ion mobility differences. The FAIMS-based separation and detection approach has been tested on over-the-counter diet pills. Following the extraction of the tablets, either by pressurized fluid extraction developed in-house or with sonication, the ephedra alkaloids were quantified using a modified isotope dilution approach. Detection limits for the alkaloids ranged from 0.1 to 3 ng/mL, and a linear range of at least 2 orders of magnitude was observed for the six analytes. The throughput of the current configuration of the FI-ESI-FAIMS-MS system is 2 min/sample, which is significantly higher than conventional chromatographic approaches. The developed FI-ESI-FAIMS-MS method has been compared with a conventional LC-UV analysis, and good agreement has been found for the major alkaloids.

Alkaloids↗
PubMed2004

Coupling capillary electrophoresis and high-field asymmetric waveform ion mobility spectrometry mass spectrometry for the analysis of complex lipopolysaccharides.

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is a new technology for atmospheric pressure, room temperature separation of gas-phase ions. The FAIMS system acts as an ion filter that can continuously transmit one type of ion, independent of mass-to-charge ratio (m/z). Capillary electrophoresis-electrospray mass spectrometry (CE-MS) has been extensively used for the analysis of complex bacterial lipopolysaccharides (LPS). The coupling of FAIMS to CE-MS provides a sensitive technique for the characterization of these complex glycolipids, permitting the separation of trace-level LPS oligosaccharide glycoforms for subsequent structural characterization using tandem mass spectrometry. This was demonstrated for LPS from nontypeable Haemophilus influenzae strain 375 following O-deacylation with anhydrous hydrazine. This strain of H. influenzae can express a triheptosyl-containing glycoform to which four hexose residues are linked forming the outer-core region of the molecule. This has been referred to as the Hex4 glycoform. Glycoforms have been identified which differ in the number of phosphoethanolamine substituents in the inner-core. With the use of CE-FAIMS, isomeric Hex4 glycoforms containing two PEtn groups were separated and characterized by MS/MS. FAIMS provided a significant reduction in mass spectral noise, leading to improved detection limits ( approximately 70 amol of the major glycoform). The extracted mass spectrum showed that the apparent noise was virtually eliminated. In addition to the reduction of chemical background, the ion current was increased by as much as 7.5 times as a result of the atmospheric pressure ion-focusing effect provided by the FAIMS system. The linearity of response of the CE-FAIMS-MS system was also studied. The calibration curve is linear for approximately 3 orders of magnitude, over a range of 40 pg/microL to 10 ng/microL.

Carbohydrate Sequence↗
PubMed2003

Characterization of naphthenic acids by electrospray ionization high-field asymmetric waveform ion mobility spectrometry mass spectrometry.

Electrospray ionization (ESI) high-field asymmetric waveform ion mobility spectrometry (FAIMS) was combined with quadrupole, time-of-flight, and tandem mass spectrometry to characterize commercial and naturally occurring naphthenic acids (NA) mixtures. This new method provides quantitatively reliable mass and isomer distributions of NA components in approximately 3 min without extensive sample preparation. ESI-FAIMS-MS seems to be especially useful for characterization of fragile ions that cannot be detected by other methods. A unique part of this technique is separation of structural isomers that proved to be critical in determination of elemental composition and in structure elucidation. Tandem mass spectrometry of NA ions separated by FAIMS provides more information about the structure of NA than other methods in the field of NA analysis.

Journal Article↗
PubMed2001

Developments in ion mobility spectrometry-mass spectrometry.

Ion mobility spectrometry (IMS) has been used for over 30 years as a sensitive detector of organic compounds. The following is a brief review of IMS and its principles with an emphasis on its usage when coupled to mass spectrometry. Since its inception, IMS has been interfaced with quadrupole, time-of-flight, and Fourier-transform ion cyclotron resonance mass spectrometry. These hybrid instruments have been employed for the analysis of a variety of target analytes, including biomolecules, explosives, chemical warfare degradation products, and illicit drugs.

Journal Article↗
PubMed1999

Detection of chlorinated and brominated byproducts of drinking water disinfection using electrospray ionization-high-field asymmetric waveform ion mobility spectrometry-mass spectrometry.

The lower limit of detection for low molecular weight polar and ionic analytes using electrospray ionization-mass spectrometry (ESI-MS) is often severely compromised by an intense background that obscures ions of trace components in solution. Recently, a new technique, referred to as high-field asymmetric waveform ion mobility spectrometry (FAIMS), has been shown to separate gas-phase ions at atmospheric pressure and room temperature. A FAIMS instrument is an ion filter that may be tuned, by control of electrical voltages, to continuously transmit selected ions from a complex mixture. This capability offers significant advantages when FAIMS is coupled with ESI, a source that generates a wide variety of ions, including solvent clusters and salt adducts. In this report, the tandem arrangement of ESI-FAIMS-MS is used for the analysis of haloacetic acids, a class of disinfection byproducts regulated by the US EPA. FAIMS is shown to effectively discriminate against background ions resulting from the electrospray of tap water solutions containing the haloacetic acids. Consequently, mass spectra are simplified, the selectivity of the method is improved, and the limits of detection are lowered compared with conventional ESI-MS. The detection limits of ESI-FAIMS-MS for six haloacetic acids ranged between 0.5 and 4 ng/mL in 9:1 methanol/tap water (5 and 40 ng/mL in the original tap water samples) with no preconcentration, derivatization, or chromatographic separation prior to analysis.

Acetates↗
PubMed2006

Compensation voltage shifting in high-field asymmetric waveform ion mobility spectrometry-mass spectrometry.

The separation and ion focusing properties of High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) depend on desolvated ions entering the device, leading to a compound-specific, reproducible compensation voltage (CV) for each ion. This study shows that the conditions identified for stable spray and satisfactory ion desolvation in normal electrospray ionization mass spectrometry (ESI-MS) operation might significantly differ from those required for FAIMS-MS. In a typical setup with high-flow electrospray conditions, ions could be incompletely desolvated, resulting in the formation of unidentified clusters with differing behavior in a FAIMS environment. This causes compound-specific shifts of as much as 10 V in CV values when the mobile phase composition and/or flow rate are varied. The shifts diminish and finally disappear when the flow rate of methanol, used as mobile phase, is reduced to 40 microL/min and that of acetonitrile to 20 microL/min. The reproducibility of the observed CV was determined by scanning the CV while infusing a five-component mixture into a 400 microL/min flow of methanol or 50:50 acetonitrile/water. The relative standard deviation (RSD) for these multiple scans ranged from 0.7% to 6%. Therefore, under a constant set of experimental parameters, the CV does not shift appreciably. These observations have an impact on method development strategies. High flow rates can be used with the FAIMS device, since the CV values are reproducible, but it is likely that clusters are forming. Therefore, CV scans should be performed under conditions which mimic the chromatographic elution or flow injection analysis conditions, including matrix composition, to minimize errors in CV determination. An alternative approach is to determine the liquid flow rate at which the CV becomes compound-specific and to split the mobile phase stream accordingly. These experimental results may be specific to the setup used for this study and may not be directly applicable to other instrument FAIMS devices.

Journal Article↗
PubMed1999

Application of high-performance liquid chromatography coupled to nuclear magnetic resonance spectrometry, mass spectrometry and bioassay for the determination of active saponins from Bacopa monniera Wettst.

Reversed-phase high-performance liquid chromatographic separation coupled to (structurally informative) spectroscopic methods like NMR and MS and an efficient bioassay have been used to determine the active compounds from a crude fraction of Bacopa monniera. The fraction containing a mixture of saponins with closely related structures was found to show a significant anthelmintic activity against Caenorhabditis elegans (used as a model test organism for determining anthelmintic activity). The activity was correlated to two dammarane type triterpenoidal saponins containing at least three sugar units. The optimization of separation for 1 mg of the crude sample on column and the sensitivity of on-flow one- and two-dimensional NMR experiments to the high-molecular-mass compounds (M(r) 890-930) has been demonstrated.

Animals↗
PubMed2002

Quantitation of amphetamine, methamphetamine, and their methylenedioxy derivatives in urine by solid-phase microextraction coupled with electrospray ionization-high-field asymmetric waveform ion mobility spectrometry-mass spectrometry.

Amphetamine, methamphetamine, and their methylenedioxy derivatives have been identified and measured in a human urine matrix using solid-phase microextraction (SPME) and high-field asymmetric waveform ion mobility spectrometry (FAIMS) in combination with electrospray ionization (ESI) and mass spectrometric detection (MS). Limits of detection in human urine between 200 pg/mL and 7.5 ng/mL have been achieved. The use of a simple extraction method, SPME, combined with the high sensitivity and selectivity of ESI-FAIMS-MS eliminates the need for chromatographic separation and allows for very rapid sample processing.

3,4-Methylenedioxyamphetamine↗
PubMed1991

Analysis of methionine enkephalin in human pituitary by multi-dimensional reversed-phase high-performance liquid chromatography, radioreceptor assay, radioimmunoassay, fast atom bombardment mass spectrometry, and mass spectrometry-mass spectrometry.

Methionine enkephalin (ME = YGGFM) was measured in five individual human post-mortem pituitaries using four different analytical methods, with the objective of comparing the molecular specificities of the methods. Radioreceptor assay (RRA) used a receptor-rich preparation from brain and [3H]etorphine as radioligand to determine ME-like receptoractivity (ME-LR). Radioimmunoassay (RIA) measured ME-like immunoreactivity (ME-LI). Pituitary samples analyzed by RRA and RIA were purified first with a high-performance liquid chromatography (HPLC) gradient on a polymer analytical column. Fast atom bombardment mass spectrometry (FAB-MS) in two different detection modes quantified ME using the protonated molecular ion MH+ of ME at 574 a.m.u. and B/E linked-field selected reaction monitoring (SRM) to monitor the specific unimolecular metastable transition that produced the unique amino acid sequence-determining tetrapeptide fragment ion YGGFA+ from the MH+ precursor ion. Both FAB-MS methods used the deuterated internal standard YGG[2H5-F]M. Samples analyzed with FAB-MS were purified first with multi-dimensional reversed-phase HPLC. The first dimension was an ODS gradient, and the second dimension was a polymer isocratic elution. The following ME amounts were measured (mean +/- standard error of the mean): ME-LR, 7.0 +/- 1.9 micrograms g-1 tissue; ME-LI, 1.8 +/- 0.7 micrograms g-1 tissue; MH+, 2.7 +/- 0.6 micrograms g-1 tissue; SRM, 3.0 +/- 0.8 micrograms g-1 tissue. The FAB SRM method provided the highest level of molecular specificity amount these four analytical methods used to measure picomole amounts of endogenous ME in a human pituitary.

Adult↗
PubMed2005

Programmable gate delayed ion mobility spectrometry-mass spectrometry: a study with low concentrations of dipropylene-glycol-monomethyl-ether in air.

The concept of using a short ionisation event, in this case a pulsed corona discharge, in conjunction with programmed gate delay is described. This technique is proposed for the selective study of different ionisation processes within the reaction region of an ion mobility spectrometer. The utility of such an approach was tested in a study of the ionisation of dipropylene-glycol-monomethyl-ether (DPM); a compound commonly used to test the operation of ion mobility spectrometers. Dipropylene-glycol-monomethyl-ether at a concentration of 113 microg m(-3) in air, with a water level of 75 mg m(-3) in air, was analysed using a switchable, high resolution ion mobility spectrometer, operating in the positive mode at 40 degrees C at ambient pressure. The ion mobility spectrometer was fitted with a pulsed corona discharge ionisation source, doped with ammonia at a concentration of 1.3 mg m(-3) in the reaction region, and interfaced to a mass spectrometer. Synchronisation of the ionisation event to the operation of the shutter grids for the drift region enabled different parts of the product ion population to be injected into the drift tube, and programming the gate delays produced a map of the gate delay verses drift time response surface. Ammonium bound dipropylene-glycol-monomethyl-ether was observed, [(DPM)NH4]+ (m/z 166) as well as the ammonium bound dimer [(DPM)2NH4]+ (m/z 314), the same as those observed with a 63Ni source. Two other species were also observed, but their molecular identity was not elucidated. One of them m/z 146, also observed with 63Ni, formed ammonium bound ions [(m/z 146)NH4]+ (K0= 1.49 cm2 V(-1) s(-1)), ammonium bound dimer ions [(m/z 146)2NH4]+(K0= 1.18 cm2 V(-1) s(-1)) and a mixed cluster ion with DPM [(m/z 146)(DPM)NH4]+(K0= 1.18 cm2 V(-1) s(-1)); while the other, m/z 88 a decomposition product, formed ammonium bound monomer [(m/z 88)NH4]+(K0= 1.68 cm2 V(-1) s(-1)), dimer ions [(m/z 88)2NH4]+(K0= 1.40 cm2 V(-1) s(-1)) and a mixed cluster ion containing DPM and ammonium, [(DPM)(m/z 88)2NH4]+(K0= 1.40 cm2 V(-1) s(-1)). The assignment of responses to these ions required the additional dimensionality in the data provided from the gate delay studies. The relationships evident in the programmable gate delay data enabled these ions to be differentiated from alternative assignments of possible nitrogen clusters, formed at the interface of the mass spectrometer.

Air↗
PubMed2001

Electrospray ionization mass spectrometry of tetrodotoxin and its analogs: liquid chromatography/mass spectrometry, tandem mass spectrometry, and liquid chromatography/tandem mass spectrometry.

Tetrodotoxin (TTX), a powerful sodium channel blocker, usually exists as a mixture of its analogs (TTXs) in natural sources. Due to the structural variation, some analogs are difficult to detect using the postcolumn liquid chromatography-fluorescent detection (LC-FLD) system. Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) analysis of TTXs can be achieved by a combination of chromatography on a reversed-phase column with long carbon chains (C30) and the mobile phase containing an ion pair reagent (ammonium heptafluorobutyrate). The relationship between the amount of applied standard TTX and its peak area on the mass chromatogram (m/z 320) showed good linearity over a range of 50-1000 pmol. The detection limit for TTX in the selected ion monitoring (SIM) mode was estimated to be 0.7 pmol (signal to noise ratio: 2). The tandem mass spectrometry (MS/MS) scan for the fragment ions of eight TTXs arising from the molecular ions provided characteristic spectra, and the structures of the origins of the prominent fragment ions were proposed. The intense fragment ions of TTX and 11-deoxyTTX were applicable to LC/MS/MS operated in the selected reaction monitoring mode. This method might be useful for further identification of TTXs.

Animals↗
PubMed2006

Comparison of flow injection analysis electrospray mass spectrometry and tandem mass spectrometry and electrospray high-field asymmetric waveform ion mobility mass spectrometry and tandem mass spectrometry for the determination of underivatized amino acids.

Twenty proteinogenic amino acids (AAs) were determined without derivatization using flow injection analysis followed by electrospray ionization mass spectrometry and tandem mass spectrometry (ESI-MS and ESI-MS/MS) and electrospray ionization high-field asymmetric waveform ion mobility mass spectrometry and tandem mass spectrometry (ESI-FAIMS-MS and ESI-FAIMS-MS/MS), in positive and negative ionization modes. Three separate sets of ESI-FAIMS conditions were used for the separation and detection of the 20 AAs. Typically ESI-FAIMS-MS showed somewhat improved sensitivity and significantly better signal-to-noise ratios than ESI-MS mainly due to the elimination of background noise. However, the difference between ESI-FAIMS-MS and ESI-MS/MS was significantly less. ESI-FAIMS was able to partially or completely resolve all the isobaric amino acid overlaps such as leucine, isoleucine and hydroxyproline or lysine and glutamine. Detection limits for the amino acids in ESI-FAIMS-MS mode ranged from 2 ng/mL for proline to 200 ng/mL for aspartic acid. Overall, ESI-FAIMS-MS is the preferred method for the quantitative analysis of AAs in a hydrolyzed yeast matrix.

Amino Acids↗
PubMed2000

Studies on neurosteroids XII. Determination of enzymatically formed catechol estrogens and guaiacol estrogens by rat brains using liquid chromatography-mass spectrometry-mass spectrometry.

Enzymic formations of catechol- and guaiacol-estrogens by rat brains have been investigated using classical- and catechol-estrogens as substrates, respectively. The incubation mixtures were pretreated with liquid-liquid and/or solid-phase extraction, and the products were identified by comparison with authentic samples using liquid chromatography-mass spectrometry (-mass spectrometry) [LC-MS (-MS)]. The enzymic activities were also determined by measuring the formed products with LC-MS.

Animals↗
PubMed1990

Characterization of O-glycosylation sites in recombinant B-chain of platelet-derived growth factor expressed in yeast using liquid secondary ion mass spectrometry, tandem mass spectrometry and Edman sequence analysis.

High-performance tandem mass spectrometry has been employed to structurally characterize intact O-linked glycopeptides and establish the complexity and extent of glycosylation for recombinant human platelet-derived growth factor B chain (rhPDGF-B) expressed in yeast. In addition, liquid secondary ion mass spectrometry (LSIMS) and Edman degradation have been employed to verify the protein sequence. LSIMS of high-performance liquid chromatographically fractionated proteolytic digests confirmed the complete amino acid sequence predicted by the human PDGF-B gene structure. Potential glycopeptides (as indicated by a mass shift of 162 or 324 Da from the mass of a predicted cleavage product) were sequenced using tandem mass spectrometry and Edman degradation. Ultraviolet matrix laser desorption mass spectrometry of rhPDGF-B dimer was used to determine the molecular weight distribution for the intact recombinant glycoprotein. In addition to the presence of unmodified peptides, corresponding peptides bearing monomannosyl moieties were found on serine 26 and threonines 20, 63, 88, 90 and 101. Further, dimannosyl moieties were found on threonines 6 and 63. These data reveal the presence of O-linked glycosylation at sites which do not fortify the concept of a consensus sequence involving proline residues, but which strengthen the concept of secondary and tertiary structure requirements. The advantages of high-energy collisionally induced dissociation analysis of O-linked glycopeptides over conventional base elimination and borohydride reduction and other mass spectrometric techniques are presented for the first time.

Amino Acid Sequence↗
PubMed2006

Analysis of single nucleotide polymorphism sites in exon 4 of the p53 gene using high-performance liquid chromatography electrospray ionization mass spectrometry tandem mass spectrometry.

Three groups of four oligonucleotides with special single nucleotide polymorphisms (SNP) sites in exon 4 of the p53 gene were analyzed with ion-pair reversed-phase high-performance liquid chromatography electrospray ionization mass spectrometry tandem mass spectrometry. The retention order of four oligonucleotides with SNPs was C < G < A < T, regardless of whether the polymorphisms were at the 3' end, the 5' end, or the middle of the oligonucleotides. The charge state of the molecular ion affects the MS/MS spectra of the oligonucleotides. SNPs at the 3' end can be easily identified from the fragmentation pattern of the 2- charge state, but not from the 3- charge state, especially from the w1 fragment. The single base may be taken as the symbol of the 5' end SNP site derived from [M3H]2, but not from the [M3H]2 charge state. The oligonucleotides with SNPs in the middle were also determined from the [M2H]2 precursor ion.

Chromatography, High Pressure Liquid↗