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Atmospheric Pressure Chemical Ionization Mass Spectrometry (atmospheric + pressure_chemical_ionization_mass_spectrometry)
Selected AbstractsUnusual atmospheric pressure chemical ionization conditions for detection of organic peroxidesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2003David Rondeau Abstract Organic peroxides such as the cumene hydroperoxide I (Mr = 152 u), the di- tert -butyl peroxide II (Mr = 146 u) and the tert -butyl peroxybenzoate III (Mr = 194 u) were analyzed by atmospheric pressure chemical ionization mass spectrometry using a water,methanol mixture as solvent with a low flow-rate of mobile phase and unusual conditions of the source temperature (,50 °C) and probe temperature (70,200 °C). The mass spectra of these compounds show the formation of (i) an [M + H]+ ion (m/z 153) for the hydroperoxide I, (ii) a stable adduct [M + CH3OH2]+ ion (m/z 179) for the dialkyl peroxide II and (iii) several protonated adduct species such as protonated molecules (m/z 195) and different protonated adduct ions (m/z 227, 389 and 421) for the peroxyester III. Tandem mass spectrometric experiments, exact mass measurements and theoretical calculations were performed for characterize these gas-phase ionic species. Using the double-well energy potential model illustrating a gas-phase bimolecular reaction, three important factors are taken into account to propose a qualitative interpretation of peroxide behavior toward the CH3OH2+, i.e. thermochemical parameters () and two kinetic factors such as the capture constant of the initial stable ion,dipole and the magnitude of the rate constant of proton transfer reaction into the loose proton bond cluster. Copyright © 2003 John Wiley & Sons, Ltd. [source] Orthogonality of silver-ion and non-aqueous reversed-phase HPLC/MS in the analysis of complex natural mixtures of triacylglycerolsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2009Michal Hol Abstract The goal of this work is the study of possibilities of two basic separation modes used in the analysis of complex triacylglycerol (TG) samples of plant oils and animal fats, i.e. non-aqueous reversed-phase (NARP) and silver-ion HPLC coupled with atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The orthogonality of both separation modes is tested for complex TG mixtures containing fatty acids (FAs) with different acyl chain lengths, different number, positions and geometry of double bonds (DBs) and different regioisomeric positions of FAs on the glycerol skeleton. The retention in NARP mode is governed by the equivalent carbon number, while the retention in silver-ion chromatography increases with the increasing number of DBs with a clear differentiation between cis - and trans- FAs. Moreover, silver-ion mode enables at least the partial resolution of regioisomeric TG mixtures including cis -/trans -regioisomers, as illustrated on two examples of randomization mixtures. Off-line 2D coupling of both complementary modes (NARP in the first dimension and silver-ion in the second dimension) yields the superior chromatographic selectivity resulting in the highest number of identified TGs ever reported for studied samples. Off-line 2D chromatograms are processed with the home-made software providing various ways of data visualization. [source] INFLUENCE OF CHEWING AND SWALLOWING BEHAVIOR ON VOLATILE RELEASE IN TWO CONFECTIONERY SYSTEMSJOURNAL OF TEXTURE STUDIES, Issue 5 2006A. BLISSETT ABSTRACT Electromyography, electroglottography and turbine airflow technology were used to characterize the chewing, swallowing and breath flow profiles of 35 subjects during the consumption of two different (a gum Arabic- and carrageenan-based) confectionery chews. Simultaneous volatile release measurements were obtained using atmospheric pressure chemical ionization mass spectrometry. Subgroups of subjects displaying different eating characteristics were identified for both products. Parameters accounting for the maximum variance (product 1, 42% and product 2, 52%) between the subgroups were chewing force, chewing rate, proportion of work and total number of chews. Volatile release measurements were significantly different between the subgroups from product 1. The impact of the different eating characteristics on volatile release from product 2 was less defined, and postulated to be a result of the contrasting textural properties. Manipulating in vivo breakdown of chewy confectionery products, by texture modification, may influence consumer's volatile release and subsequent flavor perception. [source] Thermally induced intramolecular oxygen migration of N -oxides in atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2010Xin Wang N -Oxides are known to undergo three main thermal degradation reactions, namely deoxygenation, Cope elimination (for N -oxides containing a ,-hydrogen) and Meisenheimer rearrangement, in atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The ions corresponding to these thermal degradants observed in the ensuing APCI mass spectra have been used to identify N -oxides as well as to determine the N -oxidation site when the analyte contains multiple tertiary amine groups. In this paper, we report a thermally induced oxygen migration from one N -oxide amine to another tert -amine group present in the same molecule through a six-membered ring transition state during APCI-MS analysis. The observed intramolecular oxygen migration resulted in the formation of a new isomeric N -oxide, rendering the results of the APCI-MS analysis more difficult to interpret and potentially misleading. In addition, we observed novel degradation behavior that happened after the Meisenheimer rearrangement of the newly formed N -oxide: a homolytic cleavage of the NO bond instead of elimination of an aldehyde or a ketone that usually follows the rearrangement. Understanding of these unusual degradation pathways, which have not been reported previously, should facilitate structural elucidation of N -oxides using APCI-MS analysis. 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 modesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2010Sandrine 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] Fragmentation pathways of some benzothiophene radical cations formed by atmospheric pressure chemical ionisationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2009Lisandra Cubero Herrera Polycyclic aromatic sulfur-containing compounds (PASHs) are commonly found in fossil fuels and are of considerable importance in environmental studies. This work presents detailed studies on the fragmentation patterns of radical cations formed from four representative PASHs, benzo[b]thiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, using tandem atmospheric pressure chemical ionization mass spectrometry (APCI-MS/MS). Understanding these fragmentation patterns can be a useful aid in the analysis of PASHs employing APCI or electron ionization (EI-MS/MS), either alone or in conjunction with liquid or gas chromatography. Copyright © 2009 John Wiley & Sons, Ltd. [source] Detection of technical chlordane by liquid chromatography with atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2004Hiroshi Moriwaki No abstract is available for this article. [source] Targeted lipidomics using electron capture atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2003Seon Hwa Lee There is an increasing need to be able to conduct quantitative lipidomics analyses as a complement to proteomics studies. The highest specificity for proteomics analysis can be obtained using methodology based on electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) coupled with liquid chromatography/tandem mass spectrometry (LC/MS/MS). For lipidomics analysis it is often necessary to be able to separate enantiomers and regioisomers. This can be very challenging when using methodology based on conventional reversed-phase chromatography. Normal-phase chromatography using chiral columns can provide dramatic improvements in the resolution of enantiomers and regioisomers. However, conventional ESI- and APCI-MS/MS has limited sensitivity, which makes it difficult to conduct studies in cell culture systems where only trace amounts of non-esterified bioactive lipids are present. The use of electron capture APCI-MS/MS overcomes this problem. Enantiomers and regioisomers of diverse bioactive lipids can be quantified using stable isotope dilution methodology coupled with normal-phase chiral chromatography and electron capture APCI-MS/MS. This methodology has allowed a lipidomics profile from rat epithelial cells maintained in culture to be delineated and allowed the effect of a non-selective lipoxygenase inhibitor to be assessed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Matrix effects during analysis of plasma samples by electrospray and atmospheric pressure chemical ionization mass spectrometry: practical approaches to their eliminationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2003Joachim Schuhmacher Some cases of occurrence of matrix effects (mostly ion suppression) in protein-precipitated plasma samples, and their influence on the validity of plasma concentrations and pharmacokinetic parameters, are discussed. The comparison of matrix effects using either electrospray (TurboIonspray, TISP) or atmospheric pressure chemical ionization (APCI) indicated that APCI is less prone to matrix effects. Nevertheless, TISP is usually the first choice of ionization technique since unknown thermally labile metabolites might be present in the plasma samples causing erroneous results. A high impact of ion suppression on the plasma concentrations after intravenous (i.v.) administration was found, depending on the drug formulation (vehicle). Since ion suppression caused significantly lower plasma concentrations (by a factor of up to 5.5) after i.v. dosing, the area under the curve (AUC) was underestimated and the plasma clearance was consequently erroneously high, with an impact on drug candidate selection. By simple stepwise dilution (e.g. 10-fold and 50-fold) of the supernatant of protein-precipitated plasma samples, including all calibration and quality control samples, the matrix effects were recognized and eliminated. Copyright © 2003 John Wiley & Sons, Ltd. [source] Observation of different ceramide species from crude cellular extracts by normal-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2003Benjamin J. Pettus Normal-phase high-performance liquid chromatography (NP-HPLC) coupled to atmospheric pressure chemical ionization mass spectrometry (APCI-MS) allows qualitative analysis of endogenous ceramide and dihydroceramide species from crude lipid extracts utilizing chromatographic methods readily adaptable from commonly used thin layer chromatography (TLC) conditions. Qualitative information for the species comes from observation of differences in chromatographic and mass spectrometric behavior between species. Application to the analysis of ceramide and dihydroceramide from various cell lines is demonstrated. The results show the species profile in each cell line to be unique despite growth under identical conditions. The results from APCI-MS analysis corroborate and enhance information acquired from use of the diacylglycerol kinase assay for total ceramide measurement. This technique readily allows the previously difficult distinction between ceramide and dihydroceramide species. Copyright © 2003 John Wiley & Sons, Ltd. [source] Development of a liquid chromatography/time-of-flight mass spectrometric method for the simultaneous determination of trichothecenes, zearalenone and aflatoxins in foodstuffsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2006Hiroki Tanaka A liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) method based on time-of-flight MS (TOFMS) with a real-time reference mass correction technique was developed for the simultaneous determination of Fusarium mycotoxins (nivalenol, deoxynivalenol, fusarenon X, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, HT-2 toxin, T-2 toxin, diacetoxyscirpenol, zearalenone) and Aspergillus mycotoxins (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2) in corn, wheat, cornflakes and biscuits. Samples were cleaned up with a MultiSep #226 column. Detection of the mycotoxins was carried out in exact mass chromatograms with a mass window of 0.03,Th. Calibration curves were linear from 2 to 200,ng,·,mL,1 for trichothecenes and zearalenone, and 0.2 to 20,ng,·,mL,1 for aflatoxins, by 20,µL injection. The limits of detection ranged from 0.1 to 6.1,ng,·,g,1 in foodstuffs analyzed in this study. The LC/TOFMS method was found to be suitable for the screening of multiple mycotoxins in foodstuffs rapidly and with high sensitivity, and its performance was demonstrated for the confirmation for target mycotoxins. Copyright © 2006 John Wiley & Sons, Ltd. [source] Sensitive high-performance liquid chromatography/mass spectrometry method for determination of steviol in rat plasmaRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2004L. Z. Wang The main toxicological concern of stevioside, a highly potent sweetener from S. rebaudiana, is its main metabolite, steviol. To determine very low levels of steviol in in vivo experiments, a sensitive liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) method was developed for quantifying steviol in rat plasma after oral administration of a single dose of stevioside (0.5,g/kg). The sample preparation uses liquid-liquid extraction with tert -butyl methyl ether in an acidic environment. The retention time of steviol was 10.5 min. The assay was linear over the range 2,1000,ng/mL with a lower limit of detection of 1,ng/mL. The intra- and inter-day precision were <5 and <7%, respectively, and the accuracy was in the range 95,108%. The steviol concentration profile in rat plasma was determined. Copyright © 2003 John Wiley & Sons, Ltd. [source] Analysis of pyridoquinoline derivatives by liquid chromatography/atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2001Y. Picó A method using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) has been developed for the characterization and determination of pyridoquinoline derivatives 4,6-bis(dimethylaminoethylamino)-2,8,10-trimethylpyrido[3,2-g]quinoline, 4,6-bis(dimethylaminoethoxy)-2,8,10-trimethylpyrido[3,2-g]quinoline and 4,6-bis[(dimethylaminoethyl)thio]-2,8,10-trimethylpyrido[3,2-g] quinoline, all with potential antitumor properties. LC separation was performed on a conventional C18 column using a binary mobile phase composed of acetonitrile and 50,mM aqueous ammonium formate at pH 3. The APCI mass spectra obtained showed that proton addition giving [M,+,H]+ was the common mode of ionization to the amino- and thiopyridoquinolines, whereas the alkoxypyridoquinoline was identified by the main formation of the [M,,,(C2H3)N(CH3)2,+,H]+, followed by the [M,+,H]+ ion. The LC separation conditions and MS detection parameters were optimized for the determination. The analytical method was also applied to the determination of these pyridoquinoline derivatives in fetal calf serum using liquid-liquid extraction with dichloromethane. Acceptable recovery values were obtained, ranging between 45 and 98%. Copyright © 2001 John Wiley & Sons, Ltd. [source] Thin-layer chromatography combined with diode laser desorption/atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2004Song Peng The desorption of an analyte by a continuous wave diode laser from a porous surface of a thin-layer plate covered with a graphite suspension is presented. The thermally desorbed analyte molecules are ionized in the gas phase by a corona discharge at atmospheric pressure. Therefore, both essential processes,the desorption and the ionization of analyte molecules, which are often performed in one step,are separated. The target preparation is easy and fast since no additional extraction process is required. The mass spectrometric background signal was mostly limited to the low mass range showing no interference with typical compounds of interest. In this study, the calmative and antihypertensive drug reserpine was chosen as model analyte, which is often used for specification of mass spectrometers. No fragmentation was observed because of efficient collisional cooling under atmospheric pressure. The influence of diode laser power and the composition of the graphite suspension were investigated, and a primary optimization was performed. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||