共查询到20条相似文献,搜索用时 46 毫秒
1.
Lísa M Netušilová K Franěk L Dvořáková H Vrkoslav V Holčapek M 《Journal of chromatography. A》2011,1218(42):7499-7510
Fatty acid (FA) and triacylglycerol (TG) composition of natural oils and fats intake in the diet has a strong influence on the human health and chronic diseases. In this work, non-aqueous reversed-phase (NARP) and silver-ion high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry detection and gas chromatography with flame-ionization detection (GC/FID) and mass spectrometry detection are used for the characterization of FA and TG composition in complex samples of animal fats from fallow deer, red deer, sheep, moufflon, wild boar, cock, duck and rabbit. The FA composition of samples is determined based on the GC/FID analysis of FA methyl esters. In total, 81 FAs of different acyl chain length, double bond (DB) number, branched/linear, cis-/trans- and DB positional isomers are identified. TGs in animal fats contain mainly monounsaturated and saturated FAs. High amounts of branched and trans-FAs are observed in the samples of ruminants. In NARP mode, individual TG species are separated including the separation of trans- and branched TGs. Silver-ion mode provides the separation of TG regioisomers, which enables the determination of their ratios. Great differences in the preference of unsaturated and saturated FAs in the sn-2 position on the glycerol skeleton are observed among individual animal fats. Unsaturated FAs are preferentially occupied in the sn-2 position in all animal samples except for wild boar with the strong preference of saturated FAs in the sn-2 position. 相似文献
2.
Triacylglycerols (TGs) and diacylglycerols (DGs) in 16 plant oil samples (hazelnut, pistachio, poppy-seed, almond, palm, Brazil-nut, rapeseed, macadamia, soyabean, sunflower, linseed, Dracocephalum moldavica, evening primrose, corn, amaranth, Silybum arianum) were analyzed by HPLC-MS with atmospheric pressure chemical ionization (APCI) and UV detection at 205 nm on two Nova-Pak C18 chromatographic columns connected in series. A single chromatographic column and non-aqueous ethanol-acetonitrile gradient system was used as a compromise between the analysis time and the resolution for the characterization of TG composition of five plant oils. APCI mass spectra were applied for the identification of all TGs and other acylglycerols. The isobaric positional isomers can be distinguished on the basis of different relative abundances of the fragment ions formed by preferred losses of the fatty acid from sn-1(3) positions compared to the sn-2 position. Excellent chromatographic resolution and broad retention window together with APCI mass spectra enabled positive identification of TGs containing fatty acids with odd numbers of carbon atoms such as margaric (C17:0) and heptadecanoic (C17:1) acids. The general fragmentation patterns of TGs in both APCI and electrospray ionization mass spectra were proposed on the basis of MSn spectra measured with an ion trap analyzer. The relative concentrations of particular TGs in the analyzed plant oils were estimated on the basis of relative peak areas measured with UV detection at 205 nm. 相似文献
3.
Fauconnot L Hau J Aeschlimann JM Fay LB Dionisi F 《Rapid communications in mass spectrometry : RCM》2004,18(2):218-224
Positional distribution of fatty acyl chains of triacylglycerols (TGs) in vegetable oils and fats (palm oil, cocoa butter) and animal fats (beef, pork and chicken fats) was examined by reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to atmospheric pressure chemical ionization using a quadrupole mass spectrometer. Quantification of regioisomers was achieved for TGs containing two different fatty acyl chains (palmitic (P), stearic (S), oleic (O), and/or linoleic (L)). For seven pairs of 'AAB/ABA'-type TGs, namely PPS/PSP, PPO/POP, SSO/SOS, POO/OPO, SOO/OSO, PPL/PLP and LLS/LSL, calibration curves were established on the basis of the difference in relative abundances of the fragment ions produced by preferred losses of the fatty acid from the 1/3-position compared to the 2-position. In practice the positional isomers AAB and ABA yield mass spectra showing a significant difference in relative abundance ratios of the ions AA(+) to AB(+). Statistical analysis of the validation data obtained from analysis of TG standards and spiked oils showed that, under repeatability conditions, least-squares regression can be used to establish calibration curves for all pairs. The regression models show linear behavior that allow the determination of the proportion of each regioisomer in an AAB/ABA pair, within a working range from 10 to 1000 microg/mL and a 95% confidence interval of +/-3% for three replicates. 相似文献
4.
The main constituents of plant oils are complex mixtures of TGs differing in acyl chain lengths, number and positions of double bonds, and regioisomerism. A non-aqueous reversed-phase HPLC method with acetonitrile-2-propanol gradient and 30 + 15 cm NovaPak C18 columns makes possible an unambiguous identification of the highest number of TGs ever reported for these oils, based on positive-ion APCI mass spectra. A new approach to TG quantitation is based on the use of response factors with three typical detection techniques for that purpose (APCI-MS, evaporative light-scattering detection, and UV at 205 nm). Response factors of 23 single-acid TGs (saturated TGs from C7 to C22, 7 unsaturated TGs), 4 mixed-acid TGs, diolein and monoolein are calculated from their calibration curves and related to OOO. Due to differences between saturated and unsaturated acyl chains, the use of response factors significantly improves the quantitation of TGs. 133 TGs containing 22 fatty acids with 8-25 carbon atoms and 0-3 double bonds are identified and quantified in 9 plant oils (walnut, hazelnut, cashew nut, almond, poppy seed, yellow melon, mango, fig, date) using HPLC/APCI-MS with a response factor approach. Average parameters and relative fatty acid concentrations are calculated with both HPLC/APCI-MS and GC/ FID. 相似文献
5.
Edible conifer seeds can serve as a source of triacylglycerols (TGs) with unusual Delta5 unsaturated polymethylene interrupted fatty acids (UPIFAs), such as cis-5,9-octadecadienoic (taxoleic), cis-5,9,12-octadecatrienoic (pinolenic), cis-5,11-eicosadienoic (keteleeronic) and cis-5,11,14-eicosatrienoic acids (sciadonic). Conifer seed oils from European Larch (Larix decidua), Norway Spruce (Picea abies) and European Silver Fir (Abies alba) have been analyzed by non-aqueous reversed-phase high-performance liquid chromatography (NARP-HPLC) with atmospheric pressure chemical ionisation (APCI)-MS detection. The influence of different positions of double bonds in Delta5-UPIFAs on the retention and fragmentation behavior is described and used for the successful identification of TGs in each oil. TGs containing Delta5-UPIFAs have a higher retention in comparison with common TGs found in plant oils with single methylene interrupted Delta6(9)-FAs and also significantly changed relative abundances of fragment ions in APCI mass spectra. Results obtained from HPLC/MS analyses are supported by validated GC/FID analyses of fatty acid methyl esters after the transesterification. The total content of Delta5-UPIFAs is about 32% for European Larch, 27% for Norway Spruce and 20% for European Silver Fir. In total, 20 FAs with acyl chain lengths from 16 to 24 carbon atoms and from 0 to 3 double bonds have been identified in 64 triacylglycerols from 3 conifer seed oils. 相似文献
6.
Amundson LM Owen BC Gallardo VA Habicht SC Fu M Shea RC Mossman AB Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2011,22(4):670-682
Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS
n
) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant
protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer.
Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation
patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers
was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction
products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some
of the reactions were examined by H/D exchange reactions and molecular orbital calculations. 相似文献
7.
Hsu FF Turk J Thukkani AK Messner MC Wildsmith KR Ford DA 《Journal of mass spectrometry : JMS》2003,38(7):752-763
Positive ion tandem quadrupole mass spectrometric methods for structural characterization of the subclasses of sn-glycero-3-phosphocholine (PC), including alkylacyl- and alk-1-enylacylphosphocholine and lysophosphatidylcholine (LPC), are described. Following collisionally activated dissociation, the [M + Li](+) ions generated by electrospray ionization yield abundant informative fragment ions that permit structural determination, and distinction of regioisomers among lysophosphatidylcholine can be easily achieved. In contrast, structurally informative ions arising from [M + H](+) or [M + Na](+) ions are less prominent. The most abundant ion observed in the product-ion spectra of the [M + Li](+) ions of plasmenyl- and plasmanyl-PC and of LPC arises from loss of N(CH(3))(3) ([M + Li - 59](+)). This feature permits their distinction from a product-ion spectrum arising from a diacylphosphatidylcholine, in which the [M + Li - 183](+) ion reflecting loss of phosphocholine is the most prominent. Examples for identification of various subclasses of PC in biological extracts by tandem mass spectrometry applying various constant neutral loss scannings are also shown. 相似文献
8.
Hvattum E 《Rapid communications in mass spectrometry : RCM》2001,15(3):187-190
A non-aqueous reversed-phase liquid chromatographic method coupled to electrospray ionisation (ESI) tandem mass spectrometry was developed for the analysis of triacylglycerols (TGs). The synthetic TGs studied were separated according to their equivalent carbon number with a gradient of methanol (containing 0.01% (v/v) formate adjusted to pH 5.3 with ammonia) and chloroform. ESI mass spectra of TGs yielded positive ion current signals for [M + NH(4)](+) and [M + NH(4)-RCOONH(4)](+). The mass spectra also showed signals believed to arise from [M + K](+). Collision-induced dissociation (CID) of the [M + NH(4)](+) precursor ion yielded [M + NH(4) - RCOONH(4)](+), [RCO + 74](+) and [RCO](+) product ions as aids for the structural elucidation of the TGs. In addition, [RCO - 18](+) and small amounts of [RCO - 2](+) product ions were also found. The latter ions were observed only for TGs containing unsaturated fatty acids. CID of ammoniated 1-stearoyl-2-oleoyl-3-linoleoyl-glycerol (18:0/18:1/18:2) indicated that neutral loss of the sn-2 fatty acid was energetically less favourable than loss of the fatty acid from the sn-1 or sn-3 position. 相似文献
9.
Two mass spectrometers, in parallel, were employed simultaneously for analysis of triacylglycerols in canola oil, for analysis of triolein oxidation products, and for analysis of triacylglycerol positional isomers separated using reversed-phase high-performance liquid chromatography. A triple quadrupole mass spectrometer was interfaced via an atmospheric pressure chemical ionization (APCI) interface to two reversed-phase liquid chromatographic columns in series. An ion trap mass spectrometer was coupled to the same two columns using an electrospray ionization (ESI) interface, with ammonium formate added as electrolyte. Electrospray ionization mass spectrometry (ESI-MS) under these conditions produced abundant ammonium adduct ions from triacylglycerols, which were then fragmented to produce MS/MS spectra and then fragmented further to produce MS/MS/MS spectra. ESI-MS/MS of the ammoniated adduct ions gave product ion mass spectra which were similar to mass spectra obtained by APCI-MS. ESI-MS/MS produced diacylglycerol fragment ions, and additional fragmentation (MS/MS/MS) produced [RCO](+) (acylium) ions, [RCOO+58](+) ions, and other related ions which allowed assignment of individual acyl chain identities. APCI-MS of triacylglycerol oxidation products produced spectra like those reported previously using APCI-MS. APCI-MS/MS produced ions related to individual fatty acid chains. ESI-MS of triacylglycerol oxidation products produced abundant ammonium adduct ions, even for those molecules which previously produced little or no intact molecular ions under APCI-MS conditions. Fragmentation (MS/MS) of the [M+NH(4)](+) ions produced results similar to those obtained by APCI-MS. Further fragmentation (MS/MS/MS) of the diacylglycerol fragments of oxidation products provided information on the oxidized individual fatty acyl chains. ESI-MS and APCI-MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols. 相似文献
10.
Groom CA Halasz A Paquet L Thiboutot S Ampleman G Hawari J 《Journal of chromatography. A》2005,1072(1):73-82
An Agilent 3DCE capillary electrophoresis system using sulfobutylether-beta-cyclodextrin (SB-beta-CD)-ammonium acetate separation buffer pH 6.9 was coupled to a Bruker Esquire 3000+ quadrupole ion trap mass detector via a commercially available electrospray ionization interface with acetonitrile sheath flow. The CE-MS system was applied in negative ionization mode for the resolution and detection of nitroaromatic and polar cyclic or caged nitramine energetic materials including TNT [2,4,6-trinitrotoluene, formula mass (FW) 227.13], TNB (1,3,5-trinitrobenzene, FW 213.12), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine, FW 222.26) HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, FW 296.16), and CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, FW 438.19). The CE-MS system conformed to the high-performance liquid chromatography with ultraviolet absorbance detection (HPLC-UV) and HPLC-MS reference methods for the identification of energetic contaminants and their degradation products in soil and marine sediment samples. 相似文献
11.
Kurvinen JP Rua P Sjövall O Kallio H 《Rapid communications in mass spectrometry : RCM》2001,15(13):1084-1091
Rapid analysis of molecular mass distributions of triacylglycerol (TAG) mixtures and regioisomeric structures of selected molecular mass species is possible using ammonia negative ion chemical ionization mass spectrometry utilizing sample introduction by direct exposure probe. However, interpretation of spectra and calculation of results is time consuming, thus lengthening the total analysis time. To facilitate result calculation a software package (MSPECTRA 1.3) was developed and applied to automatic processing of triacylglycerol molecular mass distribution spectra and collision induced dissociation (CID) product ion spectra. The program is capable of identifying triacylglycerol molecular mass species possessing different ACN:DB (acyl carbon number:number of double bonds) ratios on the basis of m/z values of [M - H](-) ions. In addition to such identification the program also corrects spectra for abundances of naturally occurring (13)C isotopes and calculates relative proportions of triacylglycerol molecular species in the analyzed samples. If several replicate spectra are processed simultaneously the program automatically calculates an average and standard deviation of relative proportions of molecular species. In the case of CID spectra the program identifies fatty acid fragment ions [RCO(2)](-) and the corresponding [M - H - RCO(2)H - 100](-) ions, and calculates the relative proportions of ions in both groups. These proportions are then used automatically to calculate the fatty acid combinations comprising the parent triacylglycerol molecule and the regiospecific positions of fatty acids. Processing of several replicate product ion spectra simultaneously produces averaged proportions of regioisomers comprising the parent triacylglycerol molecular species and the standard deviation of the analysis. The performance of the program was tested by analyzing triacylglycerol samples of human milk, human milk substitutes, human chylomicron and cocoa butter, and by comparing results obtained by automated processing of the data with manually calculated results. 相似文献
12.
Achiral and chiral liquid chromatographic methods utilizing mass spectrometric detection were developed to investigate the possibility of inversion of configuration at any or all of the chiral centers of the neurokinin-1 (NK-1) receptor antagonist, aprepitant (5-[[2(R)-[1(R)-(3,5-bistrifluoromethyl phenyl)ethoxy]-3(S)-(4-fluorophenyl)morpholin-4-yl]methyl]-2,4-dihydro-[1,2,4]triazol-3-one), in-vivo, following administration of the compound to man. A structure such as aprepitant, that contains three chiral centers, may exist in eight stereochemical forms or, more specifically, as four diastereoisomeric pairs of enantiomers. The four diastereoisomers were separated from each other using a ProntoSil C18 AQ HPLC column (4.6 x 100 mm, 3 microm particles) with a mobile phase composed of acetonitrile--water (47:53, v/v%). Detection was via a single quadrupole mass spectrometer that was connected to the HPLC system via an APCI interface. Analysis of post-dose plasma samples under these conditions indicated that only aprepitant and or its enantiomer were present following oral administration of the drug. Aprepitant and its enantiomer were separated using a Chiralcel OD-H HPLC column with a mobile phase composed of hexane-isopropanol (80:20, v/v%); tandem mass spectrometric detection using an APCI interface was employed. Post-dose plasma samples analyzed using the Chiracel column were found to contain only aprepitant. The results of these experiments confirm that the products of inversion of configuration at any or all of the three chiral centers of aprepitant are not detectable in human plasma samples obtained following the administration of the drug. 相似文献
13.
Electrospray ionization/tandem quadrupole mass spectrometric studies on phosphatidylcholines: the fragmentation processes 总被引:1,自引:0,他引:1
We applied low-energy collisionally activated dissociation (CAD) tandem quadrupole mass spectrometry to study the fragmentation pathways of the [M + H](+) and [M + Li](+) ions of phosphatidylcholine (PC), generated by electrospray ionization (ESI). It is revealed that the fragmentation pathways leading to loss of the polar head group and of the fatty acid substituents do not involve the hydrogens attached to the glycerol backbone as previously reported. The pathway for formation of the major ion of m/z 184 by loss of the polar head group from the [M + H](+) precursor of a diacyl PC involves the participation of the alpha-hydrogen of the fatty acyl substituents, whereas the H(+) participates in the loss of fatty acid moieties. The alpha-hydrogens of the fatty acid substituents also participate in the major fragmentation processes, including formation of [M + Li-R(x)CO(2)H](+) and [M + Li-59-R(x)CO(2)H](+) ions for the [M + Li](+) ions of diacyl PCs, when subjected to low-energy CAD. These fragmentation processes are deterred by substitution of the fatty acyl moieties with alkyl, alkenyl, or hydroxyl groups and consequentially, result in a distinct product-ion spectrum for various PC, including diacyl-, plasmanyl- plasmenyl-, and lyso-PC isomers. The alpha-hydrogens of the fatty acyl substituents at sn-2 are more labile than those at sn-1. This is reflected by the preferential loss of the R(1)CO(2)H over the R(2)CO(2)H observed for the [M + Li](+) ions of diacyl PCs. The spectrum features resulting from the preferential losses permit identification and assignment of the fatty acid moieties in the glycerol backbone. The new fragmentation pathways established by tandem and source CAD tandem mass spectra of various PC molecules, including deuterium-labeling analogs, were proposed. These pathways would clarify the mechanisms underlying the ion formations that lead to the structural characterization of PC molecules. 相似文献
14.
Sforza S Galaverna G Corradini R Dossena A Marchelli R 《Journal of the American Society for Mass Spectrometry》2003,14(2):124-135
The study of unsubstituted and disubstituted beta-cyclodextrins (beta-CDs) by ESI-mass spectrometry is reported, applying a cone-induced fragmentation in the presence of a twofold excess of sodium chloride, in order to gain information about the fragmentation of the different regioisomers. On the basis of the fragmentation pattern observed for the unsusbstituted beta-CD, a statistical model shows that the fragments generated by every regioisomer of a disubstituted CD (AB, AC, and AD) are expected to differ in their relative intensity and, therefore, they can be used for correctly identifying the three different regioisomers. The model was tested on the three regioisomeric (AB, AC, and AD) diamino-beta-CDs and ditosyl-beta-CD and on the AC and AD regioisomers of dimesitylenesulphonyl-beta-CD, allowing in every case through statistical analysis of the fragmentation pattern the correct assignment of every regioisomer on the basis of an ESI mass spectrum (single quadrupole analyzer, high cone voltage) of the pure compounds. The absolute intensities of the fragmentation peaks were voltage-dependent but their ratios was voltage-independent, indicating that no mass bias in peak ratios is introduced by the analyzer. Given the fast time of analysis and its general applicability, independently from the substituents, we propose our method as an easy way to identify the regioisomers of disubstituted beta-CDs. 相似文献
15.
T. A. Kornakova T. F. Bogdanova V. N. Piottukh-Peletskii 《Journal of Structural Chemistry》2008,49(2):224-234
The applicability of structural analogy to structure elucidation of organic compounds by searching two molecular spectroscopy databases (DBs) is examined. Using structural analogy is based on the representation of DB structures as sets of structural fragments. Of primary concern are the structural fragments that are represented in the search results of both infrared (IR) and mass spectroscopy (MS) DBs. The statistically justified estimates of the efficiency of the combined search depending on the spectral similarity are given. 相似文献
16.
Aalberg L DeRuiter J Noggle FT Sippola E Clark CR 《Journal of chromatographic science》2000,38(8):329-337
The popular drug of abuse 3,4-methylenedioxymethamphetamine (MDMA) is one of a total of 10 regioisomeric 2,3- and 3,4-methylenedioxyphenethylamines of MW 193 that yields regioisomeric fragment ions with equivalent mass (m/z 58 and 135/136) in the electron-impact (EI) mass spectrum. Thus, these 10 methylenedioxyphenethylamines are uniquely isomeric; they have the same molecular weight and equivalent major fragments in their mass spectra. The specific identification of one of these compounds (i.e., Ecstasy or 3,4-MDMA) in a forensic drug sample depends upon the analyst's ability to eliminate the other regioisomers as possible interfering or coeluting substances. This study reports the synthesis, chemical properties, spectral characterization, and chromatographic analysis of these 10 unique regioisomers. The ten 2,3- and 3,4-regioisomers of MDMA are synthesized from commercially available precursor chemicals. In the EI mass spectra, the side-chain regioisomers show some variation in the relative intensity of the major ions, with the exception of only one or two minor ions that might be considered side-chain specific fragments. The position of substitution for the methylenedioxy ring is not easily determined by mass spectral techniques, and the ultimate identification of any one of these amines with the elimination of the other nine must depend heavily upon chromatographic methods. The chromatographic separation of these 10 uniquely regioisomeric amines are studied using reversed-phase liquid chromatographic methods with gradient elution and gas chromatographic techniques with temperature program optimization. 相似文献
17.
M. Herderich E. Richling R. Roscher C. Schneider W. Schwab H. -U. Humpf P. Schreier 《Chromatographia》1997,45(1):127-132
Summary The development of techniques utilizing atmospheric pressure ionization, namely atmospheric pressure chemical ionization (APCI)
and electrospray ionization (ESI), has pioneered the coupling of liquid chromatography (HPLC) with mass spectrometry in recent
years. Both ESI and APCI generate ions from polar and labile biomaterials with remarkable ease and efficiency. In particular,
the use of HPLC with tandem mass spectrometry (MS-MS) opens further dimensions in the field of bioorganic analysis. Thus,
HPLC-MS-MS provides the tools for direct elucidation of the structure and variety of polar natural compounds in complex matrices.
In order to develop efficient and straightforward strategies for the analysis of polar natural products, the potential and
the limitations of these hyphenated analytical techniques are discussed using heterocyclic aromatic amines, fumonisins, acylated
glycoconjugates and regioisomeric fatty acid hydroperoxides as examples.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
18.
The first hyphenation of high performance liquid chromatography (HPLC), electrochemical online oxidation and mass spectrometry (MS) is described. Ferrocenecarboxylic acid esters of various alcohols and phenols have been synthesized, separated by reversed-phase HPLC and oxidized (ionized) coulometrically prior to single quadrupole MS analysis using electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) interfaces. The dependence of the ionization on the electrochemical pretreatment is demonstrated. Limits of detection for selected derivatives range from 4 x 10(-9) to 4 x 10(-7) mol dm-3 depending on the individual compound and the selected interface. 相似文献
19.
Shaoping Fu David Arráez‐Román Javier A. Menéndez Antonio Segura‐Carretero Alberto Fernández‐Gutiérrez 《Rapid communications in mass spectrometry : RCM》2009,23(1):51-59
In this work, rapid‐resolution liquid chromatography (RRLC) coupled to electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS) and ion trap multiple mass spectrometry (IT‐MSn) has been applied to separate and characterize eleven isomers of oleuropein aglycon in fourteen Spanish extra‐virgin olive oils. After the extra‐virgin olive oil sample had been dissolved in hexane and cleaned up by a diol‐bonded phase solid‐phase extraction (SPE) cartridge, the eluting extract was resolved in methanol and analyzed on an Angilent 1200 system with a 4.6 × 150 mm, 1.8 µm Zorbax Eclipse plus C18 column. Mass spectrometry was carried out on a Bruker Daltonics microTOF mass spectrometer and a Bruker Daltonics ion trap mass spectrometer. The characterization of isomers of oleuropein aglycon was based on accurate mass data and the isotope function of characteristic fragment ions in the studied compounds by TOF‐MS, and the fragment ions were further confirmed by IT‐MSn. The fragmentation pathway of oleuropein aglycon was successfully elucidated and all possible transformations among isomers of oleuropein aglycon were suggested. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
20.
An HPLC/MS-MS method was developed for the analysis of selenium species. Tandem mass spectrometry (MS-MS) was chosen as a detector to provide structural and molecular information allowing the identification of species, which are not commercially available as standards. A new separation method for selenium species was developed, based on porous graphitic carbon (PGC) as the stationary phase. The applicability of the optimized HPLC/MS-MS system was demonstrated by the analysis of a mixture containing Se-methyl-selenocysteine, selenomethionine, selenocystine, selenoethionine and selenocystamine. All peaks were baseline-resolved and eluted within 16 min. Positive ionization led to higher intensities than negative ionization. Signal suppression tests showed that electrospray ionization (ESI) is a more effective ionization method than atmospheric pressure chemical ionization (APCI) for selenium species in a matrix containing pentafluoropropionic acid, heptafluorobutyric acid or ammonium formate. Comparative experiments with a triple quadrupole mass spectrometer (Quattro LC) and a time-of-flight instrument (Q-Tof-2) showed a 20 fold higher mass resolution of the latter mass spectrometer (m/Am= 5000) and significantly lower intensities for analyte signals as well as background noise compared to the triple quadrupole instrument. MS-MS spectra of the investigated selenium species including characteristic fragmentation patterns are presented. 相似文献