Coupling with gas chromatography

Similar comments apply in the case of organics in seawater, because it has now become possible to resolve the complex mixtures of organics in seawater and achieve the required very low detection limits. Only since the advent of sample preconcentration and mass spectrometry coupled with gas chromatography and high-performance liquid chromatography, and possibly derivatisa-tion of the original sample constituents to convert them into a form suitable for chromatography, has this become possible. 

Solid-phase microextraction has also been used for to determine volatile organic compounds in soil [26]. Target compounds were adsorbed directly from a head-space sample above a soil layer onto a fused-silica fibre. Vacuum distillation coupled with gas chromatography-mass spectrometry [27], head-... 

Microwave-assisted extraction coupled with gas chromatography-electron capture negative chemical ionization mass spectrometry (i. e., MAE-GC-EC-NCI-MS) was described for the simplified determination of imidazolinone herbicides in soil at the ppb level [715]. 

Reusser, D.E. and Field, J.A. Determination of benzylsuccinic acid in gasoline-contaminated groundwater by solid-phase extraction coupled with gas chromatography-mass spectrometry. J. Chromatogr. A, 953(l-2) 215-225. 2002. 

Electron impact (El) ionization is one of the most classic ionization techniques used in mass spectrometry. A glowing filament produces electrons, which are then accelerated to an energy of 70 eV. The sample is vaporized into the vacuum where gas phase molecules are bombarded with electrons. One or more electrons are removed from the molecules to form odd electron ions (M+ ) or multiply charged ions. Solids, liquids and gases can be analyzed by El, if they endure vaporization without decomposition. Therefore the range of compounds which can be analyzed by El is somewhat limited to thermally stable and volatile compounds. The coupling with gas chromatography has been well established for... 

S. B. Hawthorne, M. S. Krieger and D. J. Miller, Analysis of flavor and fragrance compounds using supercritical fluid extraction coupled with gas chromatography , Anal. Chem. 60 472-477 (1988). 

A low resolution mass spectrometer used for routine analysis by EPA Methods 8260 and 8270 consists of three main parts an ion source, a mass analyzer (both kept under vacuum conditions), and a detector. Although a variety of GC/MS instruments with different designs are available, the most common in the environmental laboratory are those with electron impact ion sources and quadrupole mass analyzers as they are best suited for the coupling with gas chromatography columns. These stable and reliable detectors with a relatively broad linear dynamic range became the workhorses of the environmental laboratory. 

Einsle, T., H. Paschke, K. Bruns, S. Schrader, P. Popp, and M. Moeder. 2006. Membrane-assisted liquid-liquid extraction coupled with gas chromatography-mass spectrometry for determination of selected polycyclic musk compounds and drugs in water samples. J. Chromatogr. A 1124 196-204. 

Wang, J.-X., D.-Q. Jiang, and X.-P. Yan. 2006. Determination of substituted benzenes in water samples by fiber-in-tube liquid phase microextraction coupled with gas chromatography. Talanta 68 945-950. 

Several papers in this book and in the recent literature (3) discuss use of pyrolysis techniques coupled with gas chromatography and mass spectrometry to determine forms of organically bound sulfur, but these methods introduce an uncertainty due to the possible interconversion of these sulfur forms during the heating step. For example, it has been shown that when benzyl sulfide was heated to 290°C, tetraphenyl thiophene, hydrogen sulfide and stilbene were produced (4). Coupled with heat and mass transport limitation considerations, particularly for viscous liquids and solids, it is not unreasonable to question whether at least some of the thiophenic forms observed by these techniques were produced during the analysis and may not have been present in the original sample. 

Solid phase micro-extraction coupled with gas chromatography has been used to identity jet fuel components in groundwaters [511],... 

Pecoraino, G., Scalici, L., Avellone, G., Ceraulo, L., Favara, R., Candela, E.G., Provenzano, M.C., Scaletta, C. Distribution of volatile organic compounds in Sicilian groundwaters analysed by head space-solid phase micro extraction coupled with gas chromatography mass spectrometry (SPME/GC/MS). Water Res. 42(14), 3563-3577 (2008)... 

Hu, M., Chen, H., Jiang, Y., Zhu, H. Headspace single-drop microextraction coupled with gas chromatography electron capture detection of butanone derivative for determination of iodine in milk powder and urine. Chem. Pap. 67(10), 1255-1261 (2013)... 

Enteshari, M., Mohammadi, A., Nayebzadeh, K., Azadniya, E. Optimization of headspace single-drop microextraction coupled with gas chromatography-mass spectrometry for determining volatile oxidation compounds in mayonnaise by response surface methodology. Food Anal. Methods 7,438-448 (2014)... 

Wang, K.D., Chen, P.S., Huang, S.D. Simultaneous derivatization and extraction of chloro-phenols in water samples with up-and-down shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography/mass spectrometric detection. Anal. Bioanal. Chem. 406, 2123-2131 (2014)... 

Zhao, R.S., Cheng, C.G., Yuan, J.P., Jiang, T., Wang, X., Lin, J.M. Sensitive measurement of ultratrace phenols in natural water by purge-and-trap with in situ acetylation coupled with gas chromatography-mass spectrometry. Anal. Bioanal. Chem. 387, 687-694 (2007)... 

Chlorinated hydrocarbon pesticide residues in human adipose tissue and liver tissue samples have been identified by mass spectrometry coupled with gas chromatography. A general, extensive extraction and cleanup procedure adapted from existing methods was used to isolate... 

Aprea, E., Biasioli, F., Carlin, S., Versini, G., Mark, T. and Gasperi, F. (2007) Rapid white truffle headspace analysis by proton transfer reaction-mass spectrometry and comparison with solid-phase microextraction coupled with gas chromatography/mass spectrometry, Rapid Commun. Mass Sp., 21(16), 2564-2572. 

III. Use of Stable Isotopes in Studies of Drug Metabolism and Toxicology -Since the advent of mass spectrometry (ms) coupled with gas chromatography (gc-ms), stable isotopes have been used extensively in the study of drug metabolism. The use of ms in the field of drug metabolism has been reviewed, 29,30 an(j t0th reviews cover the use of stable isotopes. There are several ways in which stable isotopes have been used to study drug metabolism and these will be covered individually. 

Figures 1,2, and 3 are provided to illustrate one protocol often used to evaluate sink materials [20,32,42-47] however, other methods are also used. For example, Krebs and Guo [48] reported on a unique method involving two test chambers in series. The first chamber is injected with a known concentration of a pollutant (in this case, ethylbenzene). The outlet from the first chamber provides a simple first-order decay that is injected into the inlet of the second chamber that contains the sink material (gypsum board). Thus, this method exposes the sink test material to a changing concentration typical of many wet VOC sources. The sink adsorption rate and desorption rate results are comparable to one-chamber tests and are achieved in a much shorter experimental time. Kjaer et al. [31] reported on using a CLIMPAC chamber and sensory evaluations coupled with gas chromatography retention times to evaluate desorption rates. Finally, Funaki et al. [49] used AD PAG chambers and exposed sink materials to known concentrations of formaldehyde and toluene and then desorbed the sinks using clean air. They reported adsorption rates as a percentage of concentration differences.

Zhao, G., Liu, J.-F., Nyman, M., Jonsson, J. L. (2007). Determination of short-chain fatty acids in serum by hoUow fiber supported liquid membrane extraction coupled with gas chromatography. J. Chromatogr. B, 846, 202-8. 

Figure 5.4. The HS-SPME-GC/MS chromatograms recorded in SIM mode in the analysis of compounds reported in Table 5.5 (a) internal standards (33. d6-DMS, m/z 68 34. DPDS, m/z 108 35. MT, m/z 71 36. M ill, m/z 148), (b) analytes (37. EtSH, m/z 62 38. DMS, m/z 62 39. DES, m/z 75 40. MTA, m/z 90 41. DMDS, m/z 94 42. ETA, m/z 104 43. DEDS, m/z 122 44. ME, m/z 78 45. MTU, m/z 92 46. MTP, m/z 106 47. MTB, m/z 120 48. BT, m/z 135 49. IIMT, m/z 122).The SPME conditions are reported in Table 5.4. (Reprinted from Rapid Communications in Mass spectrometry 21, Fedrizzi et al., Concurrent quantification of light and heavy sulphur volatiles in wine by headspace sohd-phase microextraction coupled with gas chromatography/mass spectrometry, p. 710, Copyright 2007, with permission from John Whey Sons, Ltd.)...

Vianna, E. and Ebeler, S. (2001). Monitoring ester formation in grape juice fermentations using solid phase microextraction coupled with gas chromatography-mass spectrometry, J. Agric. Food Chem., 49(2), 589-595. 

Mueller, W., Schubert, J., Benzing, A., and Geiger, K., Method for analysis of exhaled air by microwave energy desorption coupled with gas chromatography-flame ionization detection-mass spectrometry, J. Chromatogr. B, 716, 27-38, 1998. 

Sarri6n, M. N., Santos, F. J., and Galceran, M. T., Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water, J. Chromatogr. A, 859, 159-171, 1999. 

Although chromatographic systems are highly sensitive, it is also true that we must be concerned with concentrations of target materials and the detectability limit of the measurement system. Because of the relatively high concentrations of major air components in most of the studies, usually no further preconcentration of the analytes is necessary prior to chromatographic analysis. In some cases, sample volumes can even be reduced down to the level of /rl. Carbon dioxide and carbon monoxide can first be reduced to methane if a flame ionization detector (FID) coupled with gas chromatography (GC) is used. However, moisture is considered a major interference and shall... 

Mass spectrometry coupled with gas chromatography (GC-MS) is a very powerful tool to identify and quantify a broad variety of thermally stable herbicides in complex environmental matrixes, as shown by the numerous literature published in the recent... 

Reidel K., Ruppert T., Conze C., Scherer G. and Adlkofer F. (1996) Determination of benzene and alkylated benzenes in ambient and exhaled air by microwave desorption coupled with gas chromatography-mass spectrometry. J. Chrom. A., 719, 383-389. 

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