scholarly journals Fragmentation studies of tetrahydropyridocarbazole derivatives by EI, ESI-MS/MS and FAB

2001 ◽  
Vol 15 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Gilberto A. Romeiro ◽  
Vitor F. Ferreira ◽  
Marília dos S. Costa ◽  
Alexandre M. Joaquim ◽  
José Walkimarde M. Carneiro ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Hydrogen Atom ◽  
Fast Atom Bombardment ◽  
Fragmentation Pathway ◽  
Diels Alder ◽  
Methyl Substituent ◽  
Main Fragmentation Pathway ◽  
Double Charge ◽  
Semi Empirical

Four tetrahydropyridocarbazole derivatives were analysed by different mass spectrometry techniques: electrospray ionization, fast atom bombardment and by low and high resolution 70 eV electron ionization. Retro Diels Alder is the main fragmentation pathway, whereas other pathways leading to [M—1]+, [M—CH3]+and double charge ions also occur to considerable extents. Semi-empirical calculation provided some evidence on the nature of tropylium ions [M—1]+. Calculation of ΔHf0indicated that [M+—1] could be formed preferentially when a hydrogen atom is lost from the methyl substituent of the homoaromatic ring.

Herbicide trace analysis by high-resolution fast atom bombardment mass spectrometry: quantification of low parts per trillion levels of atrazine in water

1993 ◽  
Vol 65 (17) ◽  
pp. 2372-2379 ◽  
Author(s):  
Kenneth A. Caldwell ◽  
V. M. Sadagopa Ramanujam ◽  
Zongwei. Cai ◽  
Michael L. Gross ◽  
Roy F. Spalding
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Trace Analysis ◽  
Fast Atom Bombardment

scholarly journals Guaianolide Sesquiterpene Lactones from Centaurothamnus maximus

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2055
Author(s):  
Taha A. Hussien ◽  
Tarik A. Mohamed ◽  
Abdelsamed I. Elshamy ◽  
Mahmoud F. Moustafa ◽  
Hesham R. El-Seedi ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Biosynthetic Pathway ◽  
Fast Atom Bombardment ◽  
Arabian Peninsula ◽  
Sesquiterpene Lactones ◽  
2D Nmr ◽  
Spectroscopic Techniques ◽  
Chemical Structures ◽  
Aerial Parts

Centaurothamnus maximus (family Asteraceae), is a leafy shrub indigenous to the southwestern Arabian Peninsula. With a paucity of phytochemical data on this species, we set out to chemically characterize the plant. From the aerial parts, two newly identified guaianolides were isolated: 3β-hydroxy-4α(acetoxy)-4β(hydroxymethyl)-8α-(4-hydroxy methacrylate)-1αH,5αH, 6αH-gual-10(14),11(13)-dien-6,12-olide (1) and 15-descarboxy picrolide A (2). Seven previously reported compounds were also isolated: 3β, 4α, 8α-trihydroxy-4-(hydroxymethyl)-lαH, 5αH, 6βH, 7αH-guai-10(14),11(13)-dien-6,12-olide (3), chlorohyssopifolin B (4), cynaropikrin (5), hydroxyjanerin (6), chlorojanerin (7), isorhamnetin (8), and quercetagetin-3,6-dimethyl ether-4’-O-β-d-pyranoglucoside (9). Chemical structures were elucidated using spectroscopic techniques, including High Resolution Fast Atom Bombardment Mass Spectrometry (HR-FAB-MS), 1D NMR; 1H, 13C NMR, Distortionless Enhancement by Polarization Transfer (DEPT), and 2D NMR (1H-1H COSY, HMQC, HMBC) analyses. In addition, a biosynthetic pathway for compounds 1–9 is proposed. The chemotaxonomic significance of the reported sesquiterpenoids and flavonoids considering reports from other Centaurea species is examined.

scholarly journals Determination of Atrazine and Hydroxyatrazine in Agricultural Runoff Waters by Liquid Chromatography and Fast Atom Bombardment-High Resolution Mass Spectrometry

1996 ◽  
Vol 79 (4) ◽  
pp. 929-935 ◽  
Author(s):  
Zongwei Cai ◽  
Steven J Monson ◽  
Roy F Spalding
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
High Resolution ◽  
Water Samples ◽  
Fast Atom Bombardment ◽  
High Resolution Mass Spectrometry ◽  
High Resolution Mass ◽  
Runoff Events ◽  
Resolution Mass

Abstract Agricultural surface water samples were collected after the first 2 major runoff events in 1994 for determination of atrazine (ATR, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and hydroxyatrazine (HA, 2-ethylamino-4-hydroxy-6-isopropylamino-striazine). After addition of. 13C3-labeled ATR and 13C3-labeled HA as internal standards, the chemicals were quantitatively extracted and eluted from water samples by liquid-solid extraction with a carbon black cartridge. Liquid chromatography and fast atom bombardment-high resolution mass spectrometry were used to analyze the sample extracts. Concentrations of ATR ranged from 8.2 to 15.1 parts per billion (ppb) in the samples collected after both runoff events from a highly agricultural watershed in south-central Nebraska. HA concentrations ranged from 0.25 to 2.7 ppb in the water samples. Results obtained from both analytical procedures agreed within a 15% deviation. As predicted from runoff events, the highest levels occurred in samples from the first collection on June 24,1994, for both ATR and HA, whereas samples collected on July 5,1994, contained much lower levels of HA.

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