in order to investigate the medicinal species from montain of shirkooh (up village), in yazd provience, iran on three species by scientific names were heracleum persicum desf. ex fisch., c.a.mey. & avé-lall.; ziziphora clinopodioides lam. and nepeta asterotricha rech.f. were collected on june, july and august 2011. then all samples essential oils were extracted by hydro-distillation method (cla...

The purpose of postmortem forensic toxicological analysis is to determine the role of any unknown drug/poison in causing death. The first and the most important step in the analysis scheme is the screening of biological specimens for the presence of drugs/poison. Currently, general unknown screening (GUS) or systemic toxicological analysis (STA) procedure involves gas chromatography-mass spectr...

The EI-MS fragmentation mechanism of the bacterial sesquiterpene epi-isozizaene was investigated through enzymatic conversion of all 15 synthetic ((13) C1 )FPP isotopomers with the epi-isozizaene synthase from Streptomyces albus and GC-MS and GC-QTOF analysis including MS-MS. A systematic method, which we wish to call position-specific mass shift analysis, for the identification of the full set...

BACKGROUND Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF MS) has been proposed as a powerful new tool for multidimensional analysis of complex chemical mixtures. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs) in normal human breath. METHODS Samples of alveolar breath VOCs and ambient ro...

The photosulfochlorination of n-tetradecane by sulfuryl chloride leads to a reaction mixture containing unreacted n-tetradecane, chloro n-tetradecanes and n-tetradecanesulfonyl chlorides. Direct and simultaneous GC analysis of the mixture of the sulfochlorinated and chlorinated isomers is followed by mass spectrometry identification of all the components either by electron impact (EI-MS) and by...

The analysis of nine explosive compounds by gas chromatography tandem mass spectrometry (GC–MS/MS) using negative chemical ionization (NCI) was performed under two different conditions: first, a conventional GC separation coupled with a standard ion dissociation method in a quadrupole ion trap (QIT) was performed in segmented selected reaction monitoring mode; second, a fast GC separation on a ...