摘要:

AbstractA directory of companies which supply mass spectrometers, components and services is provided. This directory expands on an earlier version.

ISSN:0951-4198    

DOI:10.1002/rcm.1290060202

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractThe mass spectral behavior of a series of substituted 2‐phenyl‐1,3‐dioxolanes has been studied by several ionization techniques in order to gain further insight into the basic ionization mechanisms occurring in the fast‐atom bombardment mass spectrometry. The results obtained show that in chemical ionization, ions of the type [M+H]+are predominant while [MH]+ions are observed as important species in electron ionization and fast‐atom bombardment. Comparison of the gas‐phase hydride‐ion affinities of thr chemical ionization reagent gases ammonia and isobutane with those of the loquid matrices glycerol and dithiothereitol/dithioerythritol indicates that the predomionant formation of the [MH]+ion observed in fast‐atom bombardment by hydride abstraction in the gas phase is improbable. Furthermore, comparison of the electron ionization behavior of the cyclic acetals with that observed under fast‐atom bombardment suggests that the origin of [MH]+in the latter is not related

ISSN:0951-4198    

DOI:10.1002/rcm.1290060203

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractIn Order to prevent the diffusion of sample when a matrix is deposited on the sample spot on a thin‐layer chromatography (TLC) plate and to obtain constructively high sensitivity in mass spectrometry, we developed a conedensation technique including ‘trapezoid technique’ for TLC/fast‐atom bombardment mass spectrometry (FABMS) on both silica gel and C18 plates. For colored samples and colorless samples having a chromophore, the condensation technique previously in use, that condenses the sample towards the center of the spot in a line, using methoanol, was effective. The trapezoid condensation technique has been newly developed for colorless compounds having no chromophore. The mass spectra obtained using this technique clerly showed molecular ion species at relatively lower concentrations of samples, and the technoique can improve the detection limits of molecular ion species in TLC/FABMS by 3‐100 times with good reprod

ISSN:0951-4198    

DOI:10.1002/rcm.1290060204

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractThe mechanism for the formation of y ions in the collision‐induced dissociation (CID) spectra of protonated peptides produced by fast‐atom bombardment was investigated by tandem mass spectrometry and deuterium labelling studies. The results show that a hydrogen atom attached to nitrogen and not to carbon migrates during cleavage of the amide bond. A mechanism based on these results is presen

ISSN:0951-4198    

DOI:10.1002/rcm.1290060205

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractPositive and negative secondary ions from large (up to 40 KDa) peptide and protein primary ions incident at 5–40 keV collisional energies on a stainless‐steel (mesh) conversion dynode have been investigated in a tandem (reflectron) time‐of‐flight arrangement. Negative secondary‐ion spectra consisted mainly of H−and C2H−, C2H 2−ions; positive secondary‐ion spectra were more complex and contained prominent signals due to H+, Na+and K+, and further signals atm/z. 28, 41, 43, 45, 73 up tom/z326. The secondary mass spectra were qualitatively very similar amongst the various peptide primaries and not different from those of other organic projectiles such as, for example, coronene or cyclodextrin. With increasing mass of the primary ion, ratios of the secondary‐ion abundances changed drastically in the negative secondary‐ion spectra (increase of higherm/zsignals, decrease of H−). Since most of the positive secondary ions could be attributed to a silicon‐organic surface contamination of the dynode (vacuum grease), it is concluded that the formation of such secondary ions is due to sputtering rather than s

ISSN:0951-4198    

DOI:10.1002/rcm.1290060206

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel method of peptide sequencing by mass spectrometry is described. Metastable decay of laser‐desorbedions, taking place in the first field‐free drift region of a reflectron time‐of‐flight mass spectrometer, has been monitored to get structural information from larger peptides. Fragment ions from metastable decay are mass analysed by adjusting the potentiaals of the ion reflectron according to the kinetic energies of the ions. The features of the technique and its significance for future applications are o

ISSN:0951-4198    

DOI:10.1002/rcm.1290060207

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractStructures of the fatty acid characterizing the various components of A40926 were determined by gas chromatography/mass spectrometry on the methyl esters obtained by methanolysis of the complex. The results confirm the residues previously assigned to Factor A (n‐Undecanoic acid) and B (10‐methyl‐undecanoic acid) and establish the residues of Factor A1(9‐methyl‐decanoic acid), B1 (n‐dodecanoic acid), RS1 (8‐methyl‐nonanoic acid), RS2 (n‐decanoic acid), and RS3 (n‐tridecanoic acid). As theactinomaduraspecies contain in their mycelia large quantities of C15‐C17 fatty acid residues as membrane phospholipids, these mycelia were saponified and the fatty acids obtained were analyzed as above. There is a close correlation beterrn the fatty acid content of A40923 complex and that of longer homologues in

ISSN:0951-4198    

DOI:10.1002/rcm.1290060208

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractAn analytical expression has been derived for the mass‐analyzed ion kinetic energy spectral profile resulting from a single kinetic energy release in a metastable ion decopmposition. Effects of the Z and Y discriminations and the site of dissociation on the peak‐shape have been accounted for. In addition an analytical peak‐shape function has been derived for a dissociation occurring in and near the collision cell floated at high voltage. Excellent agreement between the present results and the peak shapes obtained by regorous ion‐optical trajectory calculations support the validity of the present method. More importantly, the present method has the advantage of a tremendous reduction in computi

ISSN:0951-4198    

DOI:10.1002/rcm.1290060209

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractAn Improved liquid chromatographic/mass spectrometric (LC/MS) method utilizing gradient elution and ion‐spray ionization is described for the sensitive determination of okadaic acid and dinophysistoxin‐1, the principal toxins implicated in cases of diarrhetic shellfish poisoning. The method was used to confirm the presence of both toxins, together with a recently identified isomer of okadaic acid, dinophysistoxin‐2, in various samples of cultivated blue mussels (Mytilus edulis) from Canadian and European Waters. The method provided a mass detection limit of 0.4 ng for each toxin, thus allowing detection of 40 ng per g of whole mussel tissue (or approximately 10 ng/g if only the digestive glands were used in the assay). Quantitative results obtained by LC/MS were in good agreement with those obtained by derivatization and high‐performance liquid chromatography with fluorescence de

ISSN:0951-4198    

DOI:10.1002/rcm.1290060210

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY

摘要:

AbstractAn improved method of saxitoxin analysis in urine using continuous‐flow fast‐atom bombardment mass spectrometry was developed. Parameters studied were matrix composition, matrix flow, temperature of probe tip, probe‐tip design and sample extraxtion. Optimal detection was obtained using the following matrix composition: 5% glycerol, 0.5% acetic acid, 0.025% sodium dodecylsulfate, 0.1% polyethylene glycol (PEG) 400 and 0.5% PEG 300; probe‐tip temperature: (∼55°C); flow rate: 5 or 8μL per min.; probe tip: Olson‐Hogge design. The STX standard was detected at 200pg with signal‐to‐noise ratio of 11. The percent recovery of saxitoxin from human urine after clean‐up on a weak cation exch

ISSN:0951-4198    

DOI:10.1002/rcm.1290060211

出版商:Heyden&Son Limited    

年代:1992

数据来源: WILEY