摘要:

AbstractWe describe the kinetics‐based measurement protocol which was used for the National Institute of Standards and Technology/Environmental Protection Agency International Round Robin, and provide an interim summary report of the results. At least 50% of the QQQ instruments currently in the field potentially can provide a dynamically correct (i.e., instrument‐independent) representation of ion/molecule reacti

ISSN:0951-4198    

DOI:10.1002/rcm.1290030502

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe double‐ionization energies of CF2ClH and CFCl2H have been measured by double‐charge‐transfer spectro‐scopy and are 33.1±0.5 eV and 30.3±0.5 eV, respectively. These values are smaller than the double‐ionization energy of CF3H and larger than the double‐ionization energy of CCl3H and thus exhibit the expected decrease as the fluorine atoms are replaced successively by chlorine atoms. This trend reflects a similar trend in the singleionization energies since for all the molecules the ratio of double‐ to single‐ionization energy lies be

ISSN:0951-4198    

DOI:10.1002/rcm.1290030503

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe acid form of lovastatin, an HMG‐CoA reductase inhibitor, was analyzed by gas chromatography/negativeion chemical ionization mass spectrometry after derivatization with pentafluorobenzyl bromide and bis‐(trimethylsilyl)trifluoroacetamide (BSTFA). Mass spectrometry of this derivative produced a dominant [M–181]−ion under chemical ionization conditions using ammonia as the reagent gas. The limit of detection was approximately 2 pg injected on

ISSN:0951-4198    

DOI:10.1002/rcm.1290030504

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractA fully automated computer‐controlled system was used to generate series of different linked scans at constant B2E and constant neutral loss in the second field‐free region. This system has been shown to be suitable for deriving the amino acid sequence of oligopepti

ISSN:0951-4198    

DOI:10.1002/rcm.1290030505

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractProduct‐ion spectra derived from both protonated and hydride‐abstracted molecules of long chain esters have revealed an unusual homologous series of ions which suggest a cyclization mechanism to form stabilized bicyclodecenes or bicyclonone

ISSN:0951-4198    

DOI:10.1002/rcm.1290030506

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractLens and ion trajectory simulation programs, such as the popular program SIMION, which employ potential array relaxation methods, are very useful in designing and modifying ion lens systems. Unfortunately, these programs cannot simulate lenses of certain geometries such as quadrupoles. Several approaches for portraying static DC quadrupole lenses accurately in such programs have been investigated. These include user programming, an option in the latest version of SIMION, and array modification. The most convenient and accurate method involves modifications to the lens arrays employing relaxation techniques similar to those used in SIMION itself. These have been incorporated into a self‐contained computer program named QREFINE, which is available to interested partie

ISSN:0951-4198    

DOI:10.1002/rcm.1290030507

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractIon‐spray mass spectrometry was investigated for the analysis of three marine neurotoxins: domoic acid, saxitoxin and tetrodotoxin. All three compounds gave positive‐ion spectra with abundant ions of protonated molecules and no significant fragmentation. Domoic acid gave a negative‐ion spectrum with a strong [M–H]−ion. Tandem mass spectrometry provided useful fragment‐ion spectra for all compounds. Detection limits for flow injection analyses with selected‐ion monitoring were determined to be 30 pg for saxitoxin, 100 pg for domoic acid and 200 pg for tetrodotoxin. Combining liquid chromatography with ion‐spray mass spectrometry allowed the determination of domoic acid and some of its isomers in toxic shellfish

ISSN:0951-4198    

DOI:10.1002/rcm.1290030508

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractAb initiocalculations indicate that the ion [ONCO]−is linear, whereas [HNNCO]−is effectively coplanar. The ions may be formed by collisional activation of deprotonated hydroxy and aminocarbamates. The characteristic fragmentations of [ONCO]−and [HNNOO]−are losses of O and NH respe

ISSN:0951-4198    

DOI:10.1002/rcm.1290030509

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractA new sensitive and precise method for the determination of the isotopic enrichment of [6, 6‐D2] ghicose and concentration of glucose in plasma microsamples (20 μL) has been developed. Glucose was extracted from plasma samples by anion‐cation column‐exchange with absolute ethanol, derivatized as 1,2:3,5‐bis(butylboronate)‐6‐acetyl‐α‐D‐glucofuranose, and analysed by capillary gas chromatography/ammonia chemical‐ionization mass spectrometry. This method gives a better reproducibility and precision (variation coefficient below 1%) than methods using isobutane chemical ionization.Stable isotopes are being used increasingly to investigate energy metabolismin vivo. Recent work has involved the development of methodologies, especially mass spectrometry, to perform tracer experiments using the stable isotopes2H,13C, or15N.1–4Chemical‐ionization mass spectrometry is extensively used for the analysis of isotopically labelled amino acids.2–6In neonates and chidren, „true”︁ glucose production can be measured by the continuous infusion of the stable isotopically labelled tracer 6,6‐dideutero‐glucose (6,6‐D2‐glucose), and analytical measurement is performed using gas chromatography/electron‐ionization mass spectrometry (GC/EIMS).7Herein, we present a new, simple and sensitive method for the determination of the isotopic enrichment of [6,6‐D2]glucose and measurement of the concentration of glucose in plasma microsamples (20 μL), based on the use of capillary gas‐chromatography/ammonia chemical‐ionization mass spectrometry of 1,2

ISSN:0951-4198    

DOI:10.1002/rcm.1290030510

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractA new time‐of‐flight mass analyser compatible with conventional continuous ionization methods is described. A mass resolution atm/z2000 ofm/Δm>2000 (50% valley) is predicted for the instrument which is presently being prototyped. Sensitivity advantages over scanning instruments are also predicted for this instru

ISSN:0951-4198    

DOI:10.1002/rcm.1290030511

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY