Gas chromatography retention indices

Arey, J.S., Nelson, R.K., Xu, L., Reddy, C.M. (2005) Using comprehensive two-dimensional gas chromatography retention indices to estimate environmental partitioning properties for a compete set of diesel fuel hydrocarbons. Anal. Chem. 77 7172-7182. 

The analytical data in the OCAD is derived from four different techniques. These are nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), gas chromatography/mass spectrometry (GC/MS), and gas chromatography retention indices (GC(RI)). With a few exceptions, the OCAD contains only data of compounds that are listed in the schedules of the CWC and their derivatives of BSTFA and dimercaptotoluene. 

The types of analytical data contributed are Mass Spectra (MS), Infrared (IR) spectra, Nuclear Magnetic Resonance (NMR) spectra and Gas Chromatography Retention Indices (GC(RI)). The analytical data are contributed either in hard copy or as electronic files in acceptable formats. MS data is contributed in the electronic format. 

The electronic MS on-site databases are prepared from the certified electronic version of the OCAD (e-OCAD). This version is compiled using the NIST programs (NIST MS Search/Analysis and AMDIS) and is in the form of a NIST MS Database. The e-OCAD does not contain Gas Chromatography retention indices (GC(RI)) that are required for on-site use. To create an electronic MS onsite database, the certified version of e-OCAD, which at the moment contains only MS data, is merged with the certified (GC(RI)), which is in an excel spreadsheet. After merging these data, an AMDIS version of the database is created, which is compatible with the AMDIS software used by the on-site GC/MS equipment (for more details on the software, refer to Chapter 2 and Chapter 4) (5). The MS on-site database can be sent for an inspection as a whole database or as an extract of the whole database. AMDIS is software that is used by the GC/MS on-site equipment... 

Xu, Q.-S., Massart, D.L., Liang, Y.-Z. and Eang, K.-T. (2003) Two-step multivariate adaptive regression splines for modeling a quantitative relationship between gas chromatography retention indices and molecular descriptors. /. Chromat., 998, 155-167. 

GC—gas chromatography retention indices MS—mass spectral interpretation MSA—mass spectra match with API reference spectra. 

Structure elucidation of semiochemicals by modern NMR-techniques (including HPLC/NMR) is often hampered by the very small amounts of available material and problems in the isolation of pure compounds from the complex mixtures they are embedded in. Thus, the combination of gas chromatography and mass spectrometry, GC/MS, is frequently the method of choice. Determination of the molecular mass of the target compound (by chemical ionisation) and its atomic composition (by high resolution mass spectrometry) as well as a careful use of MS-Ubraries (mass spectra of beetle pheromones and their fragmentation pattern have been described [27]) and gas chromatographic retention indices will certainly facihtate the identification procedure. In addition, the combination of gas chromatography with Fourier-transform infrared spec-... 

Figure 6.4 Schematic example of the variation of retention with temperature in gas chromatography. Retention lines are drawn for a group of 8 solutes (e.g. homologues). Vertical dashed lines (a and b) correspond to chromatograms (a and b) in figure 6.1. Horizontal dashed lines indicate the range of optimum capacity factors.

There are many books and other sources that discuss the retention index from theoretical and practical aspects. One comprehensive book is "The Sadtler Standard Gas Chromatography Retention Index Library" [15]. This series of book (from Volume 1 to Volvune 4) provides detailed data on the retention indices for more than 2,000 compoimds under varying isothermal and temperature programming GC conditions for the purpose of the general identification of unknown compoimds. 

There have been numerous attempts to determine HLB numbers from other fundamental properties of surfactants, e.g., from cloud points of nonionics (Schott, 1969), from CMCs (Lin, 1973), from gas chromatography retention times (Becher, 1964 Petrowski, 1973), from NMR spectra of nonionics (Ben-et, 1972), from partial molal volumes (Marszall, 1973), and from solubility parameters (Hayashi, 1967 McDonald, 1970 Beerbower, 1971). Although relations have been developed between many of these quantities and HLB values calculated from structural groups in the molecule, particularly in the case of nonionic surfactants, there are few or no data showing that the HLB values calculated in these fashions are indicative of actual emulsion behavior. 

A scale was developed of relative hydrogen-bond basicity for a wide variety of compounds by means of their retention in gas chromatography. Results indicate that the... 

Davies, N.W. (1990) Gas chromatographic retention indices of monoterpenes and sesquiterpenes on methyl silicone and Carbowax 20M phase. Journal of Chromatography. Vol.503, pp. 1-24. 

Davies, W. 1990. Gas chromatographic retention indices of Monoterpens and Sesquiterpenes on methyl Silicone and Carbowax 20M phases. J. Chromatography, 50, 1—24. 

Elution volume, exclusion chromatography Flow rate, column Gas/liquid volume ratio Inner column volume Interstitial (outer) volume Kovats retention indices Matrix volume Net retention volume Obstruction factor Packing uniformity factor Particle diameter Partition coefficient Partition ratio Peak asymmetry factor Peak resolution Plate height Plate number Porosity, column Pressure, column inlet Presure, column outlet Pressure drop... 

Bentone-34 has commonly been used in packed columns (138—139). The retention indices of many benzene homologues on squalane have been determined (140). Gas chromatography of C —aromatic compounds using a Ucon B550X-coated capillary column is discussed in Reference 141. A variety of other separation media have also been used, including phthaUc acids (142), Hquid crystals (143), and Werner complexes (144). Gel permeation chromatography of alkylbenzenes and the separation of the Cg aromatics treated with zeofltes ate described in References 145—148. 

An aliquot may be removed at this stage and analyzed by either gas chromatography or thin-layer chromatography to ensure that the reaction is complete. Benzobarrelene has a retention time of ca. 5 minutes in a gas chromatographic analysis under the conditions stated in Note 6, but with a column temperature of 104°. The completion of the reaction is also indicated by a purple coloration of the precipitated sodium chloride. 

Halang, W. A., Langlais, R., and Kugler, E., Cubic Spline Interpolation for the Calculation of Retention Indices in Temperature-Programmed Gas-Liquid Chromatography, Ana/. Chem. 50, 1978, 1829-1832. 

This technique detects substances qualitatively and quantitatively. The chromatogram retention time is compound-specific, and peak-height indicates the concentration of pollutant in the air. Detection systems include flame ionization, thermal conductivity and electron capture. Traditionally gas chromatography is a laboratory analysis but portable versions are now available for field work. Table 9.4 lists conditions for one such portable device. 

Lee, M. L., Vassilaros, D. L., White, C. M., Novotny, M. Anal. Chem. 51, 1979, 768-773. Retention indices for programmed-temperature capillary-column gas chromatography of polycyclic aromatic hydrocarbons. 

Kovat s retention indexes analychem Procedure to identify compounds in gas chromatography the behavior of a compound Is Indicated by Its position on a scale of normal alkane values (for example, methane = 100, ethane = 200). ko-vats ri ten-... 

The various fractions of the forerun were analyzed employing a gas chromatography column packed with silicone gum, No. XE-60, suspended on Chromosorb P and heated to 248°. The components found (with the retention times indicated) were benzyl bromide (9.0 minutes), 2-methylcyclohexanone (5.3 minutes), and, in some cases, bibenzyl (22.6 minutes). The bibenzyl, formed by reaction of the benzyl bromide with the excess methyllithium, was identified from the infrared spectrum of a sample collected from the gas chromatograph. 

A similar in vitro system used [%] A-9-DMHP mass spectra of incubation extracts were silylated and subjected to gas chromato-graphy/mass spectrometry. Strong evidence was accumulated that the major metabolite was U-hydroxy-DMHP. Overall recovery of the metabolite was only A.7% this low yield was insufficient for confirmatory analyses by other methods, such as nuclear magnetic resonance. The low recovery indicated to the investigators that DMHP and its metabolites are much more strongly bound to tissue components than are THC and its metabolites. Sixteen hours after injection of [ HjDMHP into mice, their brains were extracted. Gas chromatography of the extracts indicated retention times identical with those of synthetic 11-hydroxy-DMHP, which accounted for 90% of the radioactivity two... 

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