Retention index libraries

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

Retention index library MS, FTIR, and NMR spectral libraries and databases... 

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. 

The Sadtler Standards Gas Chromatography Retention Index Library, Sadtler and Sanyo, 1985. 

The Sadtler Capillary GC Standard Retention Index Library, Sadtler, Philadelphia. Computer disk database, contains data on 2000 compounds on four columns. 

Sadder Standard Gas Chromatography Retention Index Library. Vnls. 1-4, Philadelphia Biu-Rad Laboratories, Sadtler Division, 1984-8S, For reviews of two-dimensional GC. see M. Adahehour. J. Beens. R, J. J. Vreuls, U. A. Th. Brinkman. Trends Anal. Chem. (TRAC). 2006.25, 438 2006,25. 540 2066,25, 726,... 

Retention time indices are available for many substances as data collections for a variety of stationary phases [14-15]. Gomputerized retention index libraries are available. Alternative RI systems have recently been reviewed by Gastello [16]. 

GC method/retention index library Retention index library nist ri 346 757 Kovats RI values for 82,868 compounds... 

The Fiehn Library is a mass spectral and retention index library for comprehensive metabolic profiling. The library comprises over 1000 identified metabohtes that are currently screened by the Fiehn laboratory. The compound list is continually extended. The Fiehn mass spectral library is commercially available for GC-quadrupole mass spectrometers from Agilent Technologies, and for GC-TOF mass spectrometers from Leco Corporation, see http //fiehnlab.ucdavis.edu/Metabolite-Library-2007/... 

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. 

Figure 15.6 shows the separation achieved for the essential oil of Coriandrum sativum using GCxGC. The identity of the compound was elucidated and confirmed primarily from the MS library matches as well as by comparing the first-dimension retention index with reference libraries. GCxGG-TOFMS allowed the identification of 81 compounds, compared with only 41 compounds identified by conventional GG-qMS. 

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. 

BZ (syn. 3-Quinuclidinyl benzilate), Retention Index 2658 (Retention Index BZ is taken from library PDF-OCAD, version 4, October 2001), CAS registry No. [6581-06-2], Schedule 2.A.03... 

Figure 1.22. GC-MS-computer total ionization-retention index plot obtained from a urine extract from a comatose patient. Labelled peaks indicate library search results and the identification of methadone, methaqualone and their metabolites (reproduced from reference...

Each component was initially identified by the GC retention index and the NIST library connected to the QP-5050 mass spectrometer, as described in previous papers. (10,11) A JNM-LA400 spectrometer (Jeol, Tokyo) was employed for recording the C-NMR spectra, CDCI3 being used as a solvent. 

The retention index system has the advantage of being based on readily available reference materials that cover a wide boiling range. In addition, the temperature dependence of retention indexes is relatively small. In 1984 Sadtier Research Laboratories introduced a library of retention indexes measured on four types of fused-silica open tubular columns. The computerized format of the database allows retention index searching and possible identity recall with a desktop computer. Measurement of retention indexes is the basis of the Rohrschneider-McReynolds scheme for classification of stationary phases in GC (see Section 27C-4),... 

Reference to the library of reference spectra shows that the unknown peak could be metoprolol. The retention index for metoprolol is given in the literature as 2080 [38]. 

Kallio et al. developed an automated procedure for the identification of individual compounds in atmospheric samples and used it for the data analysis of rural aerosol samples [32]. In this procedure, retention indexes, quality parameters (minimum required similarity, S/N value, allowed I difference between experimental and library values), modulation parameters, library files, and retention times of reference compounds were utilized to construct a program for data analysis. As output, the program listed compounds that fulfilled the required criteria. The automated procedure was compared with manual identification, and it was concluded that the automated procedure worked satisfactorily if the concentrations were sufficiently high (above ca. 10 ng/m ), but for very low concentrations (low ng/m ) manual search was more accurate. 

Alternatively, the scanned mass spectrum may be compared with a library of reference spectra, and many spectra of derivatives have been published for this purpose. This comparison step may be done by computer or manually using a variety of suitable reference publications. The comparison, when supplemented by the GC retention index, demonstrates the true power of GC-MS for the unambiguous identification of mixture components at trace levels. The choice of derivative may be influenced by that used in specialist libraries of reference spectra, e.g. methyl esters of organic acids. 

Anal)de identification relies on the comparison of a UV spectrum and a retention parameter to that of corresponding data stored in a reference library. Standardized retention-index (RI) scales have previously been used. These allow interlaboratory exchange of LC—DAD databases, enabling the use of comprehensive spectral libraries. For these to be used between laboratories, however, identical LC conditions are required, so that retention indices can be correctly applied as an identification parameter. Both isocratic and gradient programs have been used in compiling RI scales, which further complicates the sharing of UV libraries. A more common approach is to use the retention time (RT) of an analyte relative to a reference marker. The reference marker is selected in-house and tailored to the LC conditions of the laboratory. This results in a compilation of an in-house relative retention time (RRT) and UV library customized to the selected separation conditions [17,18]. 

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