Analysis oflyso-platelet activating factor by negative ion gas chromatography/mass spectrometry of the nitrobenzal acetal derivatives

1988 ◽  
Vol 16 (1-12) ◽  
pp. 207-210 ◽  
Author(s):  
A. I. Mallet
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Platelet Activating Factor ◽  
Negative Ion ◽  
Gas Chromatography Mass Spectrometry ◽  
Chromatography Mass Spectrometry

Irace Level Detection of Chlorinated Paraffins in Biological and Environmental Samples, Using Gas Chromatography/Mass Spectrometry with Negative-Ion Chemical Ionization

1985 ◽  
Vol 68 (3) ◽  
pp. 427-430
Author(s):  
Peter P Schmid ◽  
Markus D Muller
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Environmental Samples ◽  
Chemical Ionization ◽  
Negative Ion ◽  
Gas Chromatography Mass Spectrometry ◽  
Chromatography Mass Spectrometry ◽  
Biological And Environmental Samples ◽  
Chlorinated Paraffins ◽  
Negative Ion Chemical Ionization

Abstract A method is described for detection of chlorinated paraffins (CPs) in biological and environmental samples. Sample preparation includes sulfuric acid treatment followed by adsorption chromatography on ilumina, which yields the CPs in one fraction that is almost free of interfering material. Using gas chromatography/mass spectrometry j with negative-ion chemical ionization, the limit of detection is 5 ng (corresponding to the lower ppb range). CP levels of 30 ppm, 200 ppb, ' and 5 ppb were found in sewage sludge, human fat, and sediment, respectively.

Endogenous Biosynthetic Precursors of (+)-Abscisic Acid. II. Incorporation of Isotopes From ( Plus or Minus )-[2H]Abscisic Aldehyde, 18O2 and H218O

1994 ◽  
Vol 21 (3) ◽  
pp. 345 ◽  
Author(s):  
AG Netting ◽  
BV Milborrow
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Abscisic Acid ◽  
Enzyme System ◽  
Negative Ion ◽  
Gas Chromatography Mass Spectrometry ◽  
Chromatography Mass Spectrometry ◽  
Negative Ion Chemical Ionisation ◽  
Endogenous Precursor ◽  
Chemical Ionisation

Tomato shoots that had been (a) fed (�)-[2H9]abscisic aldehyde via the xylem or (b) fed H218O together with (�)-[2H9]abscisic aldehyde via the xylem or (c) exposed to 18O2 and fed (�)-[2H9]abscisic aldehyde, were then wilted. The abscisic acid present was isolated, methylated and resolved into (+)- and (-)- methyl abscisate. These methyl abscisate samples were then examined by negative ion chemical ionisation (methane) gas chromatography/mass spectrometry. The undeuteriated (+)-abscisic acid contained no 180 from H218O but did contain one 18O from 18O2. No 18O from either of these sources was present in the undeuteriated (-)-abscisic acid. It was not possible to discount the xanthophyll hypothesis for the origin of stress-induced abscisic acid on the basis of these experiments. Both (+)- and (-)- multiply deuteriated abscisic acid contained one and two 18O atoms from H218O but none from 18O2. It is postulated that this multiply deuteriated (�)-abscisic acid is formed by a separate enzyme system from that which forms endogenous stress-induced (+)-abscisic acid. On the basis of the low incor- poration of abscisic aldehyde into abscisic acid, it is suggested that the endogenous precursor of stress- induced abscisic acid is an as yet unidentified structure and that abscisic aldehyde competes with it.

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