共查询到20条相似文献,搜索用时 15 毫秒
1.
Araújo AS da Rocha LL Tomazela DM Sawaya AC Almeida RR Catharino RR Eberlin MN 《The Analyst》2005,130(6):884-889
After just simple degassing, dilution, pH adjustment and direct flow injection, characteristic fingerprint spectra of beer samples have been obtained by fast (few seconds) electrospray ionization mass spectrometry (ESI-MS) analysis in both the negative and positive ion modes. A total of 29 samples belonging to the two main beer types (lagers and ales) and several beer subtypes from USA, Europe and Brazil could be clearly divided into three groups both by simple visual inspection of their ESI(+)-MS and ESI(-)-MS fingerprints as well as by chemometric treatment of the MS data. Diagnostic ions with contrasting relative abundances in both the positive and negative ion modes allow classification of beers into three major types: P = pale (light) colored (pilsener, pale ale), D = dark colored (bock, stout, porter, mild ale) and M = malt beer. For M beers, samples of a dark and artificially sweetened caramel beer produced in Brazil and known as Malzbiers were used. ESI-MS/MS on these diagnostic beer cations and anions, most of which are characterized as arising from ionization of simple sugars, oligosaccharides, and iso-alpha-acids, yield characteristic tandem mass spectra adding a second and optional MS dimension for improved selectivity for beer characterization by fingerprinting. Direct ESI-MS or ESI-MS/MS analysis can therefore provide fast and reliable fingerprinting characterization of beers, distinguishing between types with different chemical compositions. Other unusual polar components, impurities or additives, as well as fermentation defects or degradation products, could eventually be detected, making the technique promising for beer quality control. 相似文献
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Lysoglycerophosphocholine lipids (lyso-GPC) are important intermediates in the synthesis and metabolism of glycerophosphocholine lipids which are major components of the cellular lipid bilayer. Significant differences in the collisional induced decomposition (CID) behavior were observed for each of the four different subtypes of lyso-GPC in both positive and negative ions. A major difference was observed in the initial CID product ions derived from lyso-GPC [M + H]+ with the loss of water that was very abundant for acyl lyso-GPC which have a fatty acid ester substituent at either the sn-1 or sn-2 positions. Loss of neutral water was not very prominent in the case of plasmenyl and plasmanyl lyso-GPC species. The mechanism responsible for this difference in behavior of lyso-GPC subtypes was consistent with a higher proton affinity of carboxyl carbonyl oxygen atoms and vinyl ether oxygen atoms found in acyl and plasmenyl lyso-GPC lipids, respectively, as compared to the carbinol oxygen atom common to all lyso-GPC species. Collisional activation of lyso-GPC negative ions [M - 15]- also revealed distinctive differences in product ions derived from acyl and ether lyso-GPC species. The acyl compounds showed the facile elimination of a highly stable carboxylate anion, whereas plasmenyl species underwent fragmentation with loss of a neutral aldehyde, likely a result of rearrangement involving the double bond in the vinyl ether moiety. The alkyl ether species (plasmanyl lyso-GPC lipids) did not undergo either decomposition reaction observed for the other lyso-GPC subtypes which permitted differentiation of acyl, plasmenyl, and plasmanyl lyso-GPC subtypes. 相似文献
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Marques Lde A Catharino RR Bruns RE Eberlin MN 《Rapid communications in mass spectrometry : RCM》2006,20(24):3654-3658
A fast procedure to classify perfumes and identify counterfeit samples is described. Dilution of a few microL of the sample in a 1:1 methanol/water solution is followed by detection of its major polar components via direct infusion electrospray ionization mass spectrometry (ESI-MS) in the positive ion mode. As proof-of-principle cases, three famous brands of perfumes were used. The ESI+-MS fingerprints of authentic samples were very characteristic, showing distinctive sets of polar markers for each sample. Principal component analysis (PCA) placed samples of the three perfume brands in well-defined groups. Counterfeit samples were also clearly detected owing to contrasting ESI-MS fingerprints, with PCA placing these samples far away from the authentic samples. 相似文献
4.
Electrospray ionization mass spectrometry of ginsenosides 总被引:1,自引:0,他引:1
Ginsenosides R(b1), R(b2), R(c), R(d), R(e), R(f), R(g1), R(g2) and F(11) were studied systematically by electrospray ionization mass spectrometry in positive- and negative-ion modes with a mobile-phase additive, ammonium acetate. In general, ion sensitivities for the ginsenosides were greater in the negative-ion mode, but more structural information on the ginsenosides was obtained in the positive-ion mode. [M + H](+), [M + NH(4)](+), [M + Na](+) and [M + K](+) ions were observed for all of the ginsenosides studied, with the exception of R(f) and F(11), for which [M + NH(4)](+) ions were not observed. The signal intensities of [M + H](+), [M + NH(4)](+), [M + Na](+) and [M + K](+) ions varied with the cone voltage. The highest signal intensities for [M + H](+) and [M + NH(4)](+) ions were obtained at low cone voltage (15-30 V), whereas those for [M + Na](+) and [M + K](+) ions were obtained at relatively high cone voltage (70-90 V). Collision-induced dissociation yielded characteristic positively charged fragment ions at m/z 407, 425 and 443 for (20S)-protopanaxadiol, m/z 405, 423 and 441 for (20S)-protopanaxatriol and m/z 421, 439, 457 and 475 for (24R)-pseudoginsenoside F(11). Ginsenoside types were identified by these characteristic ions and the charged saccharide groups. Glycosidic bond cleavage and elimination of H(2)O were the two major fragmentation pathways observed in the product ion mass spectra of [M + H](+) and [M + NH(4)](+). In the product ion mass spectra of [M - H](-), the major fragmentation route observed was glycosidic bond cleavage. Adduct ions [M + 2AcO + Na](-), [M + AcO](-), [M - CH(2)O + AcO](-), [M + 2AcO](2-), [M - H + AcO](2-) and [M - 2H](2-) were observed at low cone voltage (15-30 V) only. 相似文献
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Authentic samples of whisky produced in Scotland and USA and counterfeit whisky samples commercialized in Brazil have been directly submitted to electrospray ionization mass spectrometry (ESI-MS) analysis in both the negative and positive ion modes to assess the potential of this technique for simple and rapid quality control and proof of authenticity of whisky samples. ESI in the negative ion mode yields the most characteristic whisky fingerprinting mass spectra in just a few seconds by direct infusion of the samples, detecting the most polar or acidic components of each sample in their deprotonated anionic forms. No pre-treatment of the sample, such as extraction or derivatization or even dilution, is required. The analysis of the ESI(-)-MS data both by simple visual inspection but more particularly by chemometric data treatment enables separation of the whisky samples into three unequivocally distinct groups: Scotch, American and counterfeit whisky, whereas single malt and blended Scotch whiskies are also distinguished to some extent. As indicated by ESI-MS/MS analysis, the diagnostic anions are simple sugars, disaccharides and phenolic compounds. Direct infusion ESI-MS therefore provides immediate chemical fingerprinting of whisky samples for type, origin and quality control, as demonstrated herein for American, Scottish and counterfeit samples, whereas ESI-MS/MS analysis of diagnostic ions adds a second dimension of fingerprinting characterization when improved selectivity is desired. 相似文献
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Junhua Wei Ji Chen Jack Martin Miller 《Rapid communications in mass spectrometry : RCM》2001,15(3):169-181
A detailed study of the solution chemistry and mass spectrometry of six carboxylato-organogermanium compounds in aqueous solution has been carried out using electrospray ionization and MSn techniques. The different types of hydrolysis products and their probable structures, which include the oligomers and their fragment ions plus water adduct ions formed by ion-molecule reactions, are presented, e.g., HO-cyclic-(-Ge(O−)CH2CH2COO) A, HO-cyclic-(-Ge(O-cyclic-(Ge(O−)CH2CH2COO)CH2CH2COO) B, −OGeO-cyclic-(-Ge(OH)CH2CH2COO) C, and −CH=CHGeO-cyclic-(-Ge(OH)CH2CH2COO) D, etc. The proposed cyclic structures are confirmed by theoretical calculations. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Frańska M 《European journal of mass spectrometry (Chichester, England)》2005,11(1):103-106
Nucleobases and alkali metal cations, under electrospray ionisation conditions, tend to form the so-called magic number clusters (unusually stable clusters in comparison with the neighbouring ones). The effect of the ion source parameters, namely cone voltage and desolvation temperature and relative concentrations of thymine and RbCl on the [T5+Rb]+ ion abundance has been studied. 相似文献
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Hydrolysis products of organotin compounds RC(6)H(4)OCH(2)COOSn(CH(2)ph)(3) (R = o-NO(2), 1; m-NO(2), 2; p-NO(2), 3; o-CH(3), 4; o-OCH(3), 5; o-Cl, 6; o-Br, 7) and RC(6)H(3)OCH(2)COOSn(CH(2)ph)(3) (R = o,o-2CH(3), 8, o-OCH(3), p-CHO, 9; o,p-2Cl, 10), produced in aqueous acetonitrile solution, have been investigated by electrospray mass spectrometry (MS) and MS(n) techniques. The complexes [Y(2)SnXR'](-), [Y(3)SnXR'](-), [Y(3)SnX(2)R'](-), [Y(2)SnX(3)R'](-), and fragment ions of [Y(3)SnR'](-), plus abundant RC(6)H(4)(or RC(6)H(3))OCH(2)COO(-) and RC(6)H(4)(or RC(6)H(3))O(-) ions are observed in negative mode, whereas the protonated molecular ion [M + H](+), complexes [Y(2)SnXR'](+), [Y(3)SnXR'](+), [Y(2)SnX(2)R'](+), [Y(3)SnX(2)R'](+), [Y(2)SnX(3)R'](+), [Y(3)SnX(3)R'](+), as well as [YSnXR'](+), [M - CH(2)ph](+), XSn(+), (phCH(2))(3)Sn(+), phCH(2)Sn(+) (Y = &bond;CH(2)ph, X = &bond;OOCCH(2)OC(6)H(4)R(or C(6)H(3)R)) are detected in the positive mode. Water adduct ions are seen in both modes. The assignments are facilitated by agreement between observed and calculated isotopic patterns and tandem mass spectrometry studies. 相似文献
12.
Klaus Eckart Joachim Spiess 《Journal of the American Society for Mass Spectrometry》1995,6(10):912-919
Stepwise binding of biotin to streptavidin via several intermediates was monitored with electrospray ionization mass spectrometry (ESIMS). Protein ligand interactions that result in conformational changes could be recognized with ESIMS by a mass shift and a change of the average multiple charge state of this protein. In addition, mass spectrometry for the ions in the gas phase revealed a much greater strength of the noncovalent bonds between the streptavidin subunits in the tetrameric complex than between the streptavidin and biotin molecules and remarkable differences in stability for the different charge states of the biotin-streptavidin noncovalent complex. 相似文献
13.
Fifteen identified C-18 fatty acyl-containing saponin structures from Quillaja saponaria Molina have been investigated by electrospray ionization ion-trap multiple-stage mass spectrometry (ESI-IT-MS(n)) in positive ion mode. Their MS(1)-MS(3) spectra were analyzed and ions corresponding to useful fragments, important for the structural identification of Quillaja saponins, were recognized. A few key fragments could describe the structural variations in the C-3 and the C-28 oligosaccharides of the Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from the MS(1)-MS(3) spectra of these saponins, together with key fragments from these saponins and 13 previously investigated saponins, was constructed for the identification of structural elements in Quillaja saponins. Peak intensity ratios in MS(3) spectra were found to be correlated to structural features of the investigated saponins and is therefore of value for the identification of regioisomers. 相似文献
14.
Zemski Berry KA Murphy RC 《Journal of the American Society for Mass Spectrometry》2004,15(10):1499-1508
Collision-induced dissociation (CID) of the [M + H]+ of glycerophospholipids typically results in abundant fragment ions that are related to the polar head group or loss of the
polar head group. An exception to this general rule occurs for glycerophosphoethanolamines (GPEtn), which are a class of phospholipids
that can have an acyl, 1-O-alkyl, or 1-O-alk-1′-enyl group as a substituent at the sn-1 position. The CID of the [M + H]+ of diacyl-GPEtn typically results in the expected loss of the phosphoethanolamine head group (141 Da). Therefore, constant
neutral loss of 141 Da has been used as a diagnostic tool for the determination of GPEtn species in complex lipid mixtures.
One disadvantage in using constant neutral loss of 141 Da in order to determine GPEtn content in lipid mixtures is that plasmalogen
GPEtn does not undergo neutral loss of phosphoethanolamine to the same extent as diacyl-GPEtn. The current studies have used
positive ion mode electrospray tandem mass spectrometry to study the collision-induced dissociation of various GPEtn plasmalogens
present in the phospholipid membranes of human neutrophils. The CID of the [M + H]+ of plasmalogen GPEtn resulted in two prominent fragment ions; one that was characteristic of the sn-1 position and one that was characteristic of the sn-2 position. These two ions were used to detect specific molecular species of GPEtn containing esterified arachidonate (precursors
of m/z 361) present in the human neutrophil. 相似文献
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AZT H-phosphonates conjugated with steroids were synthesized and determined by positive and negative ion electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). The fragmentation pathways were investigated in detail. There are very different characteristic fragment ions in the positive and negative ion MS/MS spectra. The azide group of compounds 6a and 6b underwent either elimination of HN(3) or rearrangement to an amine in both positive and negative ion mass spectrometry. 相似文献
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Zhiyu Ju Yong Ye Donghui Wei Ruyi Zou Yufen Zhao 《International journal of mass spectrometry》2009,288(1-3):51-57
Several penta- and hexa-substituted aryloxycyclotriphosphazenes were synthesized and investigated by electrospray ionization tandem mass spectrometry (ESI-MSn). Their main fragmentation pathways are proposed based on the MSn and accurate mass data. An apparent hydrolysis reaction is an important fragmentation process exhibited in the ESI-MS/MS spectra for all of them. Also interesting is the intramolecular electrocyclic ring closure observed in ESI-MS/MS spectra of them. These observations may have some potential applications in the distinction between the mass spectra of penta- and hexa-substituted hexachlorocyclotriphosphazene derivatives. 相似文献