Gas chromatograph coupled

Sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone) and solerone (4-acetyl- y-butirrolactone) were claimed to be responsible for some aroma characteristic of flor sherries wines. These compounds are present only as traces, and are chemically unstable. A system of two gas chromatographs coupled with a four-port switching valve was used to quantitate these components without previous fractionation. The first chromatograph was equipped with an on-column injector, in order to avoid thermal degradation of sotolon in the heated injector, a DB-5 column and an FID. The second chromatograph was equipped with an on-column injector, a DB-1701 column and an FID. The method allowed quantification of solerone and sotolon at concentrations as low as a few ppb (29). 

Organic compounds are extracted from the charcoal with a small volume of a suitable solvent such as carbon disulfide or dichloromethane, then collected and injected into a capillary gas chromatograph or a capillary gas chromatograph coupled with a mass spectrometer. 

To examine variation in the quality of methyl ketones expressed by females and newly-emerged males, we determined the number of unique methyl ketones expressed by individual snakes and compared the relative concentrations of individual methyl ketones comprising the overall pheromone profiles for the two groups. The methyl ketones present in the pheromone extracts were identified by gas chromatography / mass spectrometry (Hewlett Packard 5890 Series II gas chromatograph coupled with a Hewlett Packard 5971 Series mass selective detector— see LeMaster and Mason 2003 for full description of the GC/MS platform and methods). 

P33 Analyses wereper/ormed on a gas chromatograph equipped with an electron capture detector (ECD) and a gas chromatograph coupled to a mass-selective detector working in mass spectrometry-mass spectrometry (MS-MS) mode, to achieve better limits of detection and selectivity. The proposed method yields high sensitivity, good linearity, precision, and accuracy. (From Dellinger et ah, 2001)... 

We use a GC Top 8000 gas chromatograph coupled with a PolarisQ ion-trap mass spectrometer and equipped with an AI3000S autosampler (Thermofinnigan www. thermo.com). The steroids are separated on a DB-1 crosslinked methyl-silicone column, 15 mx 0.25 mm i.d., film thickness 0.25 pm (J W Scientific marketed by Agilent). Helium is used as a carrier gas at a constant pressure of about 35 kPa. A 1-pl aliquot of the final derivatized extract is injected into the system operated in splitless mode (valve opened at 2 min). The GC temperature program is the same described before for the quadrupole GC-MS system. The injector and transfer lines are kept at 260°C and 280°C, respectively. The ion source temperature is 225°C. A damping gas flow of helium is applied to the ion trap. 

A gas chromatograph coupled to a MC-ICP-MS for the precise determination of isotope ratios as part of the speciation application has been described, for example, for the elements S, Pb, Hg and Sb.2 Transient signals of sulfur isotope ratios (32S/34S) have been measured in an isotopic gas standard (PIGS 2010, IRMM) to determine SF6 using GC-MC-ICP-MS (Isoprobe, Micromass, UK) with a hexapole collision cell.42 For data evaluation of chromatographic peaks, peak integration limits were defined by the determination of a uniform isotope ratio zone inside... 

The procedures for irradiation, collection, and analysis of the volatile compounds have all been described (1, 2, 3, 5, 7, 9, 11). A cryogenically programmed gas chromatograph coupled to a rapid scanning mass spectrometer provided for the analysis of the volatile components isolated from several irradiated meats and lipid substances (6). These studies have now been extended to include other component substances in order to acquire still further understanding of the source of the irradiation-induced volatile compounds from among the various meat constituents. 

The concentrated samples were also analyzed by GC/MS using a Varian 3400 gas chromatograph coupled to a Finnigan MAT 8230 high resolution mass spectrometer. Spectra were recorded on a Finnigan MAT SS 300 Data System. GC conditions were the same as described above. 

Figure 19.1. A Varian 3800 gas chromatograph coupled to a flame ionization detector and a Varian CP-8400 automatic injector operated by Varian Star Workstation Software Version 5.

Fig, 6.13 Schematic diagram of a multifunctional GC-IRMS system. The device consists of a gas chromatograph coupled to an isotope ratio mass spectrometer via a pyrolysis or a combustion interface a, b and c for oxygen, hydrogen and carbon isotope analysis, respectively, and is additionally equipped with an elemental analyser (EA). After [205] with kind permission of the American Chemical Society... 

In some cases, additional work may be required to identify unknown compounds. One of the best ways is to use a gas chromatograph coupled to a mass spectrometer. When gas chromatography-mass spectrometry. (GC-MS) is performed to identify unknown compounds, it is easiest to chose the same stationary phase used in the original run. Capabilities of GC-MS may not allow for the same column dimensions to be utilized, but temperature programming can be altered to mimic the retention times on the non-GC-MS run. 

Products were characterized using a Varian 2700 Gas Chromatograph coupled with a EhiPont 21-490 B Mass Spectrometer. The data were obtained through a Hewlett-Packard 2100 A computer. Molecular weights of eluted fractions were determined using a MC Chromalytics Mass Chromatograph. Details have been described17 ... 

Hydrogenation of oi-xylene was carried out in a conventional flow reactor at conversions less than 10 %. The reactant was o-xylene from Phillips (99.99 %). Hydrogen (756.3 Torr) was saturated with vapors of o-xylene at 14°C (3.7 Torr) and passed through the reactor. The products of the reaction were analyzed in a gas chromatograph coupled to the reactant system, the only products detected were 1,2 cis and trans dimethylcyclohexane. Activity per site (TOF) and selectivity were calculated for t=0. 

A very useful innovation in sample introduction systems is the use of a gas chromatograph coupled to a mass spectrometer. In effect, the mass spectrometer acts in the role of detector. In this technique, known as gas chromatography-mass spectrometry (GC-MS), the gas stream emerging from the gas chromatograph is admitted through a valve into a tube, where it passes over a molecular leak. Some of the gas stream is thus admitted into the ionization chamber of the mass spectrometer. In this way it is possible to obtain the mass spectrum of every component in a mixture being injected into the gas chromatograph. 

The use of mass spectrometry in the structural analysis of carbohydrates, first reported in 1958 (114), was developed in detail by Kochetkov and Chizhov (115). They showed that, under electron impact, the acetylated and methyl ether derivatives of monosaccharides provided a wealth of structural information through analysis of typical fragmentation pathways of the initial molecular ion. This has proved of enormous utility in the structural elucidation of polysaccharides and complex oligosaccharides sequential permethylation, hydrolysis, reduction to the alditol, and acetylation, affords mixtures of peracetylated, partially methylated alditol acetates that can be separated and analyzed by use of a gas chromatograph coupled directly to a mass spectrometer (25). The mass spectra of stereoisomers are normally identical, while the gas chromatographic retention times readily permit differentiation of stereoisomers. 

All samples were extraeted with diehloromethane in an automatic extractor (Biichi B-811). Surrogate recovery standards (D8-naphthalene, DlO-phenanthrene, D12-perylene) were spiked on each PUF and QFF prior to extraction. The volume was reduced after extraction under a gentle nitrogen stream at ambient temperature, and fractionation achieved on a silica gel column. Samples were analyzed using a GC-MS (gas chromatograph coupled with a mass spectrometer) HP 5975 with a J W Scientihc fused silica column DB-5MS, 5% Ph for PAHs. Terphenyl was used as an internal standard. Detection and quantification limits were controlled by laboratory and field blanks, are site dependent and were reported elsewhere (Lammel et al. 2009b). 

At the instant t = 0, the reactor is put under pressure by the water, the pressure being applied by a movable piston in a cylinder. At the instant t = tj., lying between 14 h and 1 month, the gold capsule is removed from the apparatus, placed in a recipient which is emptied the ampoule is then pierced, the products are taken out and analysed by gas-phase chromatography and GCMS (Gas Chromatograph coupled to a Mass Spectrometer). 

GC and LC procedures may then be used to confirm the TLC results, as well as being used to quantify the level of each component. These chromatographic techniques, moreover, have the added advantage that they may also be used to identify and quantify the monomeric and plasticizer components of the formulation (Figures 3 and 4). As stated previously, either narrow or wide bore capillary columns may be used for GC analysis. Preferred stationary phases are OVI (poly(dimethylsiloxane)) and OV17 (poly(phenylmethylsiloxane)). Flame ionization is the usual mode of detection, but where unambiguous confirmation of peak identity is required, a gas chromatograph coupled to a bench-top mass spectrometer may be used (GC-MS). 

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