Mass retention index

Kovat s retention index (p. 575) liquid-solid adsorption chromatography (p. 590) longitudinal diffusion (p. 560) loop injector (p. 584) mass spectrum (p. 571) mass transfer (p. 561) micellar electrokinetic capillary chromatography (p. 606) micelle (p. 606) mobile phase (p. 546) normal-phase chromatography (p. 580) on-column injection (p. 568) open tubular column (p. 564) packed column (p. 564) peak capacity (p. 554)... 

GC-EAD Gas chromatography combined with an EAG detector GC-MS Gas chromatography combined with mass spectrometry HPLC High performance liquid chromatography KI Kovats retention index... 

Today, GC-MS (see Section 4.1.1) is a golden standard for detection and quantification of drugs and poisons volatile under GC conditions, whereas nonvolatile compounds require LC-MS (see Section 4.1.2). The GC-MS technique is much more popular for identification purposes than LC-MS, because of the easy availability of the reference mass spectra for many xenobiotics and their derivatives, either in printed or computer form. The most popular libraries are the NIST library, which contains the mass spectra of 130,000 compounds, the Wiley Registry of Mass Spectral Data, which contains 390,000 reference spectra, and the Pfleger-Maurer-Weber library, with 6,300 mass spectra and other data, such as chromatographic retention indexes. 

Schuberth J. 1994. Joint use of retention index and mass spectrum in postmortem test for volatile organics by headspace capillary gas chromatography with ion-trap detection. J Chromatogr A 674 63-71. 

W. Jennings and T. ShSoaxnoto, Qualitative Analysis of Flavor andFragrance Volatiles by Glass Capillary Gas Chromatography, Academic Press, Inc., New York, 1980 also includes retention indexes and mass spectral data. 

When identifying an eluted compound by comparing its mass spectrum with a mass spectral library, false matches are frequent. If retention index is used as a second characteristic, false matches are reduced. 

The VOCs in the inside air are enriched by means of active sampling on Tenax TA tubes, which are thermodesorbed. After internal standards have been added, analysis is carried out by capillary GC—MS. The hundred compounds on the chromatogram which have the most intense signals are identified by retention index and mass spectrum (Wensing, Schulze and Salthammer, 2002), and are then semi-quantitatively evaluated with toluene as the reference substance. The toluene equivalents are summed, and this result serves as a semi-quantitative estimation of the total VOC concentration (TVOC). 

Identification of these components was based on GC/MS and retention index information. Novel compounds were isolated by preparative capillary gas chromatography and spectroscopically identified by interpretation of infrared, nuclear magnetic resonance and mass spectra. In... 

Retention index library mass chromatography interpretation and search for specific chemical shifts and couplings... 

GC retention index and mass spectral software/ database AMDIS (Automated Mass Spectrometry Deconvolution and Identification System). The AMDIS is distributed with the OCAD for free to SPs. 

In this system, amphetamine, 3,4-methylenedioxyamphetamine (MDA) and the A-methyl and A-ethyl analogues of the drugs were derivatized, with 4-chloroamphetamine being used as the internal standard. For powders, solutions were prepared at concentrations of 1 mgml in methanol and a 100 til aliquot blown dry under nitrogen. To the residue was added 50 p.1 of 0.5 M KOH and 500 p,l of toluene. The mixture was then shaken for 30 s and centrifuged, after which the toluene layer was recovered and HFBA (5 til) added. The excess reagent was neutralized with 500 p,l of 10% NaHCOs and an aliquot (1 ttl) analysed by GC-MS. Each of the amphetamines and the A-alkylated derivatives could be separated and identified on the basis of retention index and mass spectral data. 

A typical chromatographic separation is presented in Figure 5.1. The compounds are identified in GC-MS analysis on the basis of two pieces of information, namely the retention time (or relative retention index) and mass spectral data. 

The assignment of each alcohol residue, however, was checked by synthesis starting from the lactone of 2-hydroxyglutaric acid with a two step esterification. Table 1 shows a collection of our results concerning GC-0 evaluation together with retention index and mass spectral data. The sensory properties of compoimd 1 are described as weak, fatty, lactone-like. 

The samples were analyzed by capillary gas chromatography and gas chromatography/mass spectrometry (GC/MS). Identifications were verified by comparing the component s mass spectmm and experimental retention index (I) with that of an authentic reference standard. The retention system proposed by Kovats (12) was utilized. When standards were not available the identifications were considered tentative. 

Mass spectrum and chromatographic retention index match those of an authentic reference compound. 

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