Home About us Contact
|
Home About us Contact | ||
|
|
||
Ion Chromatograms (ion + chromatogram)
Selected AbstractsIsomerization of delta-9-THC to delta-8-THC when tested as trifluoroacetyl-, pentafluoropropionyl-, or heptafluorobutyryl- derivatives,,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2008Justin M. Holler Abstract For GC,MS analysis of delta-9-tetrahydrocannabinol (delta-9-THC), perfluoroacid anhydrides in combination with perfluoroalcohols are commonly used for derivatization. This reagent mixture is preferred because it allows simultaneous derivatization of delta-9-THC and its acid metabolite, 11-nor-delta-9-THC-9-carboxylic acid present in biological samples. When delta-9-THC was derivatized by trifluoroacetic anhydride/hexafluoroisopropanol (TFAA/HFIPOH) and analyzed by GC,MS using full scan mode (50,550 amu), two peaks (P1 and P2) with an identical molecular mass of 410 amu were observed. On the basis of the total ion chromatogram (TIC), P1 with a shorter retention time (RT) was the major peak (TIC 84%). To identify the peaks, delta-8-THC was also tested under the same conditions. The RT and spectra of the major peak (TIC 95%) were identical with that of P1 for delta-9-THC. A minor peak (5%) present also correlated well with the latter peak (P2) for the delta-9-THC derivative. The fragmentation pathway of P1 was primarily demethylation followed by retro Diels-Alder fragmentation (M , 15,68, base peak 100%) indicating P1 as a delta-8-THC-trifluoroacetyl compound. This indicated that delta-9-THC isomerized to delta-8-THC during derivatization with TFAA/HFIPOH. Similar results were also observed when delta-9-THC was derivatized with pentafluoropropionic anhydride/pentafluoropropanol or heptafluorobutyric anhydride/heptafluorobutanol. No isomerization was observed when chloroform was used in derivatization with TFAA. In this reaction, the peaks of delta-8-THC-TFA and delta-9-THC-TFA had retention times and mass spectra matching with P1 and P2, respectively. Because of isomerization, perfluoroacid anhydrides/perfluoroalcohols are not suitable derivatizing agents for analysis of delta-9-THC; whereas the TFAA in chloroform is suitable for the analysis. Published in 2008 by John Wiley & Sons, Ltd. [source] Analysis of intracellular short organic acid-coenzyme A esters from actinomycetes using liquid chromatography-electrospray ionization-mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2007Je Won Park Abstract A method employing silicone oil density centrifugation, solid-phase extraction (SPE) cleanup, and LC-ESI-MS/MS analysis was developed for the rapid, selective, sensitive, and quantitative detection of an intracellular pool of short organic acid-CoA esters in actinomycetes. The detection limit was determined to be approximately 0.8 pmol (1.2 ng/ml) for each standard CoA-ester analyzed by the present LC-ESI-MS/MS method. A selected ion chromatogram for a typical fragment ion (m/z 428) specific to CoA-esters enabled the detection of eight intracellular CoA-esters involved in both primary and secondary metabolisms. The application of this method to bacterial metabolomic study is demonstrated by the profiling of the intracellular CoA-ester pools in the wild-type Streptomyces venezuelae strain producing polyketide antibiotics (methymycin and pikromycin), a polyketide synthase (PKS)-deleted S. venezuelae mutant, and a S. venezuelae mutant expressing the heterologous PKS genes. By quantifying the individual CoA-esterlevel in three different genotypes of the S. venezuela e strain, further insight could be gained into the role of CoA-estersin polyketide biosynthesis. This analytical approach can be extended to the quantification of the size and composition of in vivo CoA-ester pools in various microbes, and can provide a detailed understanding of the relationship between the in vivo CoA-ester pool and the production of pharmaceutically important polyketides. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analysis of Volatile Compounds in Beef Fat by Dynamic-Headspace Solid-Phase Microextraction Combined with Gas Chromatography,Mass SpectrometryJOURNAL OF FOOD SCIENCE, Issue 5 2008A. Watanabe ABSTRACT:, A solid-phase microextraction (SPME) technique has been applied to the determination of the volatile compounds, including diterpenoids and lactones, in cooked beef fat. The ability of static-headspace SPME to extract lactones was disappointing, regardless of the type of SPME fiber or the temperature used. Dynamic-headspace SPME extraction with 50-/30-,m divinylbenzene-Carboxen on a polydimethylsiloxane fiber at 100 °C, by contrast, enabled the analysis of volatiles, including delta-lactones, gamma-lactones, and diterpenoids, with 50-/30-,m divinylbenzene-Carboxen on a polydimethylsiloxane fiber at 100 °C. Fifty-three compounds were identified from only 0.20 g of rendered beef fat, and 76% of these showed reliable peak size repeatability: the coefficient of variation was less than 10% on the total ion chromatograms obtained from gas chromatography,mass spectrometry (GC,MS) analysis. Some lactones showed higher CV values (>10%), but single-ion mode GC,MS analysis reduced them to 10% or less. In a study of beef samples available to the Japanese market, our analytical procedure revealed significantly higher levels of 1-hexanol, octadecane, ethyl tetradecanoate, gamma-nonalactone, but lower levels of delta-decalactone, delta-dodecalactone, and neophytadiene, in Japanese Black cattle than in beef imported from Australia. [source] Studies on lignan constituents from Schisandra chinensis (Turcz.) Baill. fruits using high-performance liquid chromatography/electrospray ionization multiple-stage tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2007Xin Huang Abstract A reversed-phase high-performance liquid chromatography-diode array detector-electrospray ionization multiple-stage tandem mass spectrometry (RP-HPLC-DAD-ESI-MSn) method has been developed for the detection and analysis of lignan constituents in the methanol extract from the fruits of Schisandra chinensis (Turcz.) Baill. RP-HPLC-DAD-ESI-MSn and electrospray ionization Fourier transform ion cyclotron resonance multiple-stage tandem mass spectrometry (ESI-FT-ICR-MSn) have been applied to investigate the characteristic product ions of four lignan reference compounds. Then, the logical fragmentation pathways of the lignans have been proposed. By comparing the retention time (tR) of HPLC, the ESI-MSn data and the structures of analyzed compounds with the data of reference compounds and in the literature, 11 peaks in HPLC have been unambiguously identified and another 5 peaks have been tentatively identified or deduced. Also, in the present paper, the extracted ion chromatograms (EIC) have been used to analyze the lignan isomers. The experimental results demonstrate that RP-HPLC-DAD-ESI-MSn is a specific and useful method for the identification of the lignan constituents and their isomers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Metabolites of an orally active antimicrobial prodrug, 2,5-bis(4-amidinophenyl)furan-bis- O -methylamidoxime, identified by liquid chromatography/tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2004Lian Zhou Abstract DB75 (2,5-bis(4-amidinophenyl)furan) is a promising antimicrobial agent against African trypanosomiasis and Pneumocystis carinii pneumonia. However, it suffers from poor oral activity in rodent models for both infections. In contrast, a novel prodrug of DB75, 2,5-bis(4-amidinophenyl)furan-bis- O -methylamidoxime (DB289), has excellent oral activity. DB289 is currently undergoing clinical investigation as a candidate drug to treat primary stage African trypanosomiasis and Pneumocystis carinii pneumonia. In this study, metabolites of DB289 formed after incubation with freshly isolated rat hepatocytes were characterized using liquid chromatography/ion trap mass spectrometry. Administration of DB289 and octadeuterated DB289 in a 1 : 1 mixture greatly facilitated metabolite identification by providing isotope patterns with twin ions separated by 8 m/z units in the ratio 1 : 1, in the extracted ion chromatograms of molecular ions and in the product ion mass spectra of metabolites. Ten metabolites were identified. Series of O -demethylations and N -dehydroxylations led to the metabolic activation of DB289 to DB75 with the production of four intermediate phase I metabolites. Phase II glucuronidation and sulfation led to the formation of four glucuronide and one sulfate metabolites. Copyright © 2004 John Wiley & Sons, Ltd. [source] Real-time reaction monitoring by probe electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Zhan Yu Probe electrospray ionization (PESI) is a modified version of the electrospray ionization (ESI), where the capillary for sampling and spraying is replaced by a solid needle. High tolerance to salts and direct ambient sampling are major advantages of PESI compared with conventional ESI. In this study, PESI-MS was used to monitor some biological and chemical reactions in real-time, such as acid-induced protein denaturation, hydrogen/deuterium exchange (HDX) of peptides, and Schiff base formation. By using PESI-MS, time-resolved mass spectra and ion chromatograms can be obtained reproducibly. Real-time PESI-MS monitoring can give direct and detailed information on each chemical species taking part in reactions, and this is valuable for a better understanding of the whole reaction process and for the optimization of reaction parameters. PESI-MS can be considered as a potential tool for real-time reaction monitoring due to its simplicity in instrumental setup, direct sampling with minimum sample preparation and low sample consumption. Copyright © 2010 John Wiley & Sons, Ltd. [source] High-speed separation and characterization of major constituents in Radix Paeoniae Rubra by fast high-performance liquid chromatography coupled with diode-array detection and time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2009E-Hu Liu A fast high-performance liquid chromatography (HPLC) method coupled with diode-array detection (DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) has been developed for rapid separation and sensitive identification of major constituents in Radix Paeoniae Rubra (RPR). The total analysis time on a short column packed with 1.8-µm porous particles was about 20,min without a loss in resolution, six times faster than the performance of a conventional column analysis (115,min). The MS fragmentation behavior and structural characterization of major compounds in RPR were investigated here for the first time. The targets were rapidly screened from RPR matrix using a narrow mass window of 0.01,Da to restructure extracted ion chromatograms. Accurate mass measurements (less than 5,ppm error) for both the deprotonated molecule and characteristic fragment ions represent reliable identification criteria for these compounds in complex matrices with similar if not even better performance compared with tandem mass spectrometry. A total of 26 components were screened and identified in RPR including 11 monoterpene glycosides, 11 galloyl glucoses and 4 other phenolic compounds. From the point of time savings, resolving power, accurate mass measurement capability and full spectral sensitivity, the established fast HPLC/DAD/TOFMS method turns out to be a highly useful technique to identify constituents in complex herbal medicines. Copyright © 2008 John Wiley & Sons, Ltd. [source] The detection of phenotypic differences in the metabolic plasma profile of three strains of Zucker rats at 20 weeks of age using ultra-performance liquid chromatography/orthogonal acceleration time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2006Robert S. Plumb Analysis of biological fluids using ultra-performance liquid chromatography/mass spectrometry (UPLC/MS) (metabonomics) can allow new insights to be gained into disease processes, with advances in chromatographic techniques enabling the detection of thousands of metabolites. In this work metabonomics has been used to investigate the metabolic processes involved in type II diabetes in the Zucker obese rat. Plasma was analyzed from three different strains, the Zucker (fa/fa) obese, Zucker lean and the lean/(fa) obese cross. Using UPLC/MS, ca. 10,000 ions were detected due to the narrow peak widths and excellent peak shapes achieved with this technology. Confidence in the chromatographic performance was demonstrated by the use of quality control standards. The positive and negative ion total ion chromatograms obtained from the three strains were readily distinguishable using multivariate statistical analysis. The greatest difference was observed between the Zucker lean and Zucker lean/(fa) rats compared to the Zucker (fa/fa) obese rats. Positive ions m/z 220 (4.36,min), 282(3.78,min), 359 (5.33,min) and 405 (7.77,min) were elevated in the plasma derived from Zucker lean rats whilst ions m/z 385 (6.80,min) and 646 (4.36,min) were at a lower concentration compared to the plasma from the Zucker (fa/fa) obese animals. Negative ions elevated in the Zucker lean rats included m/z 212 (2.30,min), 514 (2.85,min), 295 (4.39,min), 329 (3.11,min), 343 (2.86,min) and 512 (2.86,min) with ions m/z 538 (4.18,min), 568 (4.18,min), 568 (5.09,min) and 612 (4.30,min) being raised in the samples derived from Zucker (fa/fa) obese animals. The ion m/z 514 (3.85,min) was found to correspond to taurocholate, providing further support for an involvement of taurine metabolism in diabetes. Copyright © 2006 John Wiley & Sons, Ltd. [source] ,All-in-One' analysis for metabolite identification using liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry with collision energy switchingRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2005Mark Wrona The removal of bottlenecks in discovery stage metabolite identification studies is an ongoing challenge for the pharmaceutical industry. We describe the use of an ,All-in-One' approach to metabolite characterization that leverages the fast scanning and high mass accuracy of hybrid quadrupole time-of-flight mass spectrometry (QqToFMS) instruments. Full-scan MS and MS/MS data is acquired using collision energy switching without the preselection, either manually or in a data-dependent manner, of precursor ions. The acquisition of ,clean' MS/MS data is assisted by the use of ultrahigh-performance chromatography. Data acquired using this method can then be mined post-acquisition in a number of ways. These include using narrow window extracted ion chromatograms (nwXICs) for expected biotransformations, XICs for the product ions of the parent compound and/or expected modification of these product ions, and neutral loss chromatograms. This approach has the potential to be truly comprehensive for the determination of in vitro biotransformations in a drug discovery environment. Copyright © 2005 John Wiley & Sons, Ltd. [source] An HPLC-MS method for simultaneous estimation of ,,, -arteether and its metabolite dihydroartemisinin, in rat plasma for application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2003M. Rajanikanth Abstract This manuscript reports, the development and validation of a sensitive and selective assay method for simultaneous determination of ,,, -arteether and its metabolite dihydroartemisinin (DHA) in rat plasma by liquid chromatography,mass spectrometry. Chromatographic separations were achieved by gradient elution of the analytes with an initial composition of methanol,potassium acetate buffer (pH 4; 73:27, v/v) to 100% methanol in 3 min and maintained for 5 min on a Spheri-10, RP18 (100 × 4.6 mm i.d.) column following an RP18 (30 × 4.6 mm i.d.) guard column. The total ef,uent from the column was split so that one-tenth was injected into the electrospray LC/MS interface. ESI-MS analysis was performed using a Micromass Quattro II Triple Quadrupole Mass Spectrometer equipped with an electrospray source. The MS analysis was carried out at cone voltage of 22 V with a scan range of 200,500 Da. The analytes were quanti,ed from the [M+ K]+ ion chromatograms of ,,, -arteether at m/z 352, DHA at m/z 323, artemisinin at m/z 321 and propyl ether analogue of arteether at m/z 365. Liquid,liquid extractions with a combination of n -hexane and hexane,ethyl acetate (8:2) were used to isolate ,,, -arteether and DHA from rat plasma. The method was validated and gave good accuracy and precision for the studied domain. Linearity in serum was observed over the range 4.375,70 ng/mL for a -arteether and 10,160 ng/mL for , -arteether and DHA. Percentage bias (accuracy) and within- and between-assay precision were well within the acceptable range. This method was applied to study the pharmacokinetics following oral administration of ,,, -arteether (30 mg/kg) in rats. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||