GC-EIMS

Glycosyl-linkages were determined by GC-EIMS of the partially methylated alditol acetates. RG-II samples (2 mg) were methylated using sodium methyl sulfmyl carbanion and methyl iodide in dimethyl sulfoxide [24] followed by reduction of the uronosyl groups with lithium triethylborodeuteride (Superdeuteride , Aldrich) [23,25]. Methylated and carboxyl-reduced samples were then submitted to acid hydrolysis, NaBIlt reduction and acetylation, partially methylated alditol acetates being analysed by EIMS on two fused-silica capillary columns (DB-1 and DB-225) [20]. 

PA-1 was partially hydrolyzed with O.IM TFA (40°C, 24 h) and the three fractions (PA-l-I, PA-l-II and PA-l-III) were obtained by Bio-gel P-6. Especially, about 50% of TBA-positive material (PA-l-III) was eluted in the fraction of small oligosaccharide. Permethylated oligosaccharide-alditols from PA-l-III were analyzed by GC-EIMS, and three disaccharide-alditols (IP, 2P and 3P) were detected. EI-MS and component sugar analysis suggested that the major peak, IP was Rha-(l- 5)-Kdo-ol and the minor peaks, 2P and 3P were two epimers of Araf-( l->5)-Dha. 

GC-EIMS Gas chromatography coupled to electron ionization mass spectrometry... 

Microscopic examination showed the pupae of the Mexican bean beetle Epilachna varivestis to be covered with glandular hairs, each having a droplet of oil at its tip. Attygalle and co-workers undertook a chemical analysis of this secretion, which resulted in the identification of a novel family of alkaloids, the azamacrolides [40]. Five compounds (27-31) (Fig. 6) were identified by GC-EIMS from the secretion, with epilachnene (27) comprising over 90% of the volatile material. 

GC mass spectrometry analysis in electron impact mode (GC/EIMS) ... 

Four nitrogen- and/or phosphorus-containing chemicals were tentatively identified through direct injection of the sample by GC/NPD. Subsequent confirmation was achieved by running the same aliquot by GC/EIMS, under similar chromatographic conditions and using the same stationary phase column, although hydrocarbons from diesel were present in... 

GC/EIMS Aliquot EOAC3 GC/CIMS Aliquot EOAC3... 

Chemicals for which no GC/EIMS library spectra was available in the OPCW Central Analytical Database (OCAD), the Wiley Registry of Mass Spectral Data, and the NIST98-NIST/EPA/NIH Mass Spectral Library, at the time of the proficiency test... 

The synthesis of R was accomplished via the alcohols 73 and 74 in the same manner as in the synthesis of P in Scheme 22. The spectral data for R ( H-, l3C-NMR, GC-FTIR, GC-EIMS) were completely identical with those for the natural product. Thus, the structure of natural 223A is revised To R, and the relative stereo structure of this alkaloid was determined to be 5R, 6R, 8R, 9S by the present synthesis[32]. 

We performed experimental research on stability assessment of RVX and identification of its transformation products under the action of equimolar or excess amoimts of water. The method for analysis was GC-EIMS. In a dilute aqueous solution (lOmg/ml) in the presence of 5% phosphoric acid, the concentration of RVX after exposiue for 20 days at room temperature without stirring was 2.7 mg/ml or 27% of the initial amoimt. Since among RVX hydrolysis products both volatile and nonvolatile compounds could be expected, we ehose three schemes for sample preparation ... 

Experiments on RVX hydrolysis with an equimolar amount of water were performed as follows. A mixture of 74 pi of RVX and 5.6 pi of water was exposed at room temperature for 3.5 months without stirring. An ash-gray thiek uniform material formed after hydrolysis and completely dissolved in 5 ml acetonitrile. The solution was diluted 100 times with acetonitrile and analyzed by GC-EIMS (sample D). An aliquot of this sample was mixed with an equal volume of bis-trimethylsilyltrifluoroacetamide (BSTFA), and the mixture was heated at 70°C for 30 min and then analyzed by GC-EIMS (sample E). The autocatalytic hydrolysis of RVX was almost complete by the end of the experiment, since the RVX content in the sample was no more than 0.01%. Qualitatively, the reaction mixture in the latter case was much poorer than in the hydrolysis with... 

Proton NMR spectra of Xlyoglucans and GC-EIMS of methylated alditol acetates. 

The molecular characterization of methylarsonic acid, phenylarsonic acid and the inorganic anion, arsenate, found in a methanol extract of a Green River Formation Oil shale sample was accomplished by HPLC-GFAA analysis In addition, derivatization of the acids, HPLC purified, by reaction with 3-methylcatechol to form the five coordinate organoarsenic catecholates as well as reaction, via trimethylsilylation, of the ammonium salt of arsenate to form tristrimethylsilylarsenate was followed by GC-EIMS analysis to provide unequivocal evidence for the presence of these organometallic and inorganic compounds of arsenic as natural products in oil shale ... 

We purified the methanol extract by preparative HPLC (the area from 22 to 35 min. was collected, Figure 1) and lyophilized the extract before dissolving in benzene. To this solution was added excess 3-methylcatechol and the reaction mixture was refluxed for 5 h and worked up to remove the excess 3-methylcatechol. A concentrated sample was subjected to GC-EIMS analysis to provide spectra and scan numbers (retention times) that were identical to the known samples of the 3-methylcatecholates of both methyl- and phenylarsonic acids. 

Figure 2. GC-EIMS analysis of the 3-methylcatecholates of methyl- and phenylarsonic acids. Key A, reconstructed ion chromatogram of known methyl- and phenylarsonic acid derivatives of3-methylcatechol B, selected ion chromatogram showing m/e 197for each derivative C, selected ion chromatogram for methylarsonic acid-3-methylcatecho-late at m/e 212 and D, selected ion chromatogram for phenylarsonic acid-3-methyl-...

Photolytically degraded PBO was re-examined by GC-EIMS at a higher mass spectrometer resolution (5000) with PFK in the mass spectrometer source as an internal mass calibrant. This procedure permits the accurate mass measurement of molecular and key fragment ions and hence the determination of their elemental compositions and fragmentation pathways. This information, along with the molecular weight information (GC-CIMS) and the low-resolution GC-EIMS spectrum, allows a structure to be proposed for each of the degradation compounds observed. 

Authentic samples of 3,4-meihylcncdioxy-6-propylbenzyl alcohol MDB alcohol) and 3,4-methylenedioxy-6-propylbenzoic acid (MDB acid) were provided by Endura SpA, Italy. An authentic sample of 3,4-me thylenedi ox y-6-propyl-benzaldehyde (MDB aldehyde) was provided by Biological Test Centre (BTC), California. These three samples were analysed by GC-EIMS and retention data and mass spectra used to investigate the presence of these compounds in photolytically degraded PBG. 

A portion of the photolytically degraded PBO was treated with diazoniethane to methylate any acid functions present. Half of this methylated sample was treated with MSTFA (Af-methy l-Af-lrimethy Isilyl-tri Auorcacetamide) to tri methyl sily I ate any alcohol groups. The two derivatized samples were examined under the standard GC-EIMS conditions used for the photolytically degraded PBO and the data obtained were compared with the data from (he photolytically degraded PBO. 

After concentration, this extract was examined by EIMS using a heated solids probe. The probe was heated from ambient to 500CC at 50°C min whilst the VG AutoSpecE mass spectrometer was scanned from 950 to 25 amu at 5 s per decade in El mode at low resolution. The sample was also analysed using the standard GC-EIMS conditions. The TLC plate was left on the bench for 2 days, at which point all of the spots had changed colour to match the darkest spot. 

The GC-EIMS chromatogram from a blended composite PBO sample is shown in Fig. 6.1. 

The authentic reference samples of safrole and dihydrosafrole showed single peaks by GC-EIMS. whilst isosafrole gave two peaks, assumed to be the errand traits- isomers. The mass spectra of the two isosafrole isomers were similar to that of safrole, but the three retention times were different. GC-EIMS mass chromatography is. therefore, an appropriate screening method for the presence of safrole, isosafrole and dihydrosafn.de in photo y tic ally degraded PBO. There was no evidence for the presence of safrole or isosafrole. However, trace quantities (< c. 10 ppm) of dihydrosafrole were detected. 

The GC-EIMS chromatogram from PBO phoiolytically degraded in sunlight in Menorca is shown in Fig. 6.3. A number of relatively major chromatographic peaks are observed which are absent or much smaller in the composite unde-graded PBO sample (Fig. 6.1). These peaks have been labelled as A-H on Fig. 

The GC-EIMS chromatograms from the methylated and methylated/ trimethysilylated photoly tic ally degraded PBO are shown in Fig. 6 A As well as assisting in the GC-EIMS analysis and identification of some of the more polar components (see below), derealization assisted in the identification of components A-H by highlighting free hydroxyl groups. 

Figure 6.4. GC-EIM S c hromaiograms of deri vatized pholol y tical ly degraded PBO-...

Figure 6.9. GC-EIMS chromatograms of phoiolylically degraded PBO and authentic MDB aldehyde.

The extract of the pink/red coloured spot from the TLC plate was examined under the standard GC-EIMS conditions and by probe El MS. The fraction proved lo be a very complex mixture of components. However, no compounds were observed which could bo responsible for the colour. At least seven components were identified by mass spectrometry, including butyl carbitol, a phenol (component LI and (wo alcohols (components M and N ... 

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