NIST Mass Spectral Library

Some of the peak assignments given in Table 6.7.2 are tentative. For example, the spectrum for the peak eluting at 97.91 min. was assigned to 3-ethyl-2H-1-benzopyran-2-one by similarity to the spectrum of 3-methyl-2H-1-benzopyran-2-one available in the NIST mass spectral library. The two spectra are shown in Figure 6.7,3. 

The GC-MS retention time and mass spectra of peak B are closely matched with the retention time and mass spectra of hydroquinone standard. The mass spectra of hydroquinone also show the same M+ peak at m/e 194 and [M-AC2]+ peak at m/e 110 as peak B. In addition, the mass spectra of peak B also closely match those of the acetylated hydroquinone in the computer database of the National Institute of Science and Technology (NIST) mass spectral library. That is, peak B corresponds to acetylated hydroquinone. 

The National Institute of Standards and Technology (NIST) Mass Spectral Library is the most widely used mass spectral reference library, which presently contains a collection of about 200 000 electron impact (El) mass spectra verified... 

Databases such as the NIST Mass Spectral Library (107,216 organic compounds, 5,943 duplicates or stereoisomeric pairs detected in the 1998 version) or the Maybridge Combinatorial Chemistry Database (MayDec02CCeus, 13,410 compounds with 19 duplicates) were processed by MOLGEN-CID. 

NIST/EPA/NIH, National Institute of Standards and Technology (NIST), U.S. Department of Commerce, Gaithersburg, MD, USA. NIST Mass Spectral Library 98 Version, 1998. 

Identification of volatile compounds in strawberries and sliced bread headspace was performed in full scan mode (m/z 30-550). Carvacrol and thymol were identified by a combination of the NIST mass spectral library and gas chromatographic retention times of standard compounds. The rest of volatiles were tentatively identified by their GC/MS spectra. In this sense, the compounds having 90% similarity with spectra in the NIST library were not taken into consideration. Chromatographic responses of detected volatile compoimds (peak area cormts) were monitored for comparative measurements of each compotmd in the studied samples. 

When your sample has been run, you will have an opportunity to search the NIST mass spectral library to determine the structures of the product(s) of the nitration. Determine the structures of the product(s) and the percentages of each component. There will likely be starting material left in the reaction mixture. It would be of interest to see how your product ratios compare to the values obtained from the literature (see References). 

The deconvolution step is greatly facilitated by using the AMDIS program and the NIST mass spectral library search program (Mallard and Reed, 1997). Unique compound mass spectra are extracted by the analysis of all the transient ion signals allocating ion masses and relative intensities for each of the eluting compounds. 

We thank the DuPont Company for providing the resources for the preparation of this book. VG Fisons and NIST also have graciously permitted the use of spectra from their mass spectral libraries. Roger Patterson,... 

Comparison with mass-spectral libraries is the easiest way of interpreting mass spectra (and often the only way for non-mass spectroscopists). The NIST/EPA/NIH (NIST 02) electron-ionisation mass spectral library... 

Provided El spectra have been measured under some sort of standard conditions (70 eV, ion source at 150-250 °C, pressure in the order of 10 " Pa), they exhibit very good reproducibility. This is not only the case for repeated measurements on the same instrument, but also between mass spectrometers having different types of mass analyzers, and/or coming from different manufacturers. This property soon led to the collection of large El mass spectral libraries, either printed [76-78] or computerized. [79] The best established El mass spectral databases are the NIST/EPA/NIH Mass Spectral Database and the Wiley/NBS Mass Spectral Database, each of them giving access to about 120,000 evaluated spectra. [80-83]... 

GC/MS was the primary tool for identifying the first DBFs, and it remains an important tool for measuring and identifying new DBFs. Large mass spectral libraries (NIST and Wiley databases, which contain >200,000 spectra) enable rapid identifications. When DBFs are not present in these databases, high-resolution... 

NIST Standard Reference Database 1A, NIST/EPA/NIH Mass Spectral Library with Search Program (Data Version NIST 02, Software Version 2.0). 

The Wiley Registry of Mass Spectral Data, commercially available at John Wiley Sons, Inc., http //www.wiley.com/cda/ product/0 0471515930 desc 3047,00.html - The NIST98-NIST/EPA/NIH Mass Spectral Library, commercially available at the National Institute of Standards and Technology, http //www.sisweb.com/software/ ms/nist98.htm) and... 

Chemicals for which no GC/EIMS library spectra was available in the OPCW Central Analytical Database (OCAD), the Wiley Registry of Mass Spectral Data, and the NIST98-NIST/EPA/NIH Mass Spectral Library, at the time of the proficiency test... 

Numerous mass spectra of tocopherols and tocotrienols have been published and many are available in the NIST/EPA/NIH Mass Spectral Library (2011) and MassBank (2011). In addition to the above chromatographic and nonchromatographic methods for tocol analysis, kits are also commercially available for the ELISA (Enzyme-linked im-munoabsorbent assay) of vitamin E. 

The peak identification for the chromatogram shown in Figure 6.1.25 was done using MS spectral library searches. This identification is not always possible, since most compounds with a higher MW are not found in the commercial mass spectral libraries (such as NIST 2002, Wiley 7. etc.). The similarity between the spectra in each series of compounds can be used for peak identification, even when the compound is not found in the mass spectral library. This is exemplified in Figure 6.1.26, which shows the spectra of the B series of compounds shown in Table 6.1.10. 

The pyrogram of poly(2-vinylpyridine-co-styrene) is typical for a random copolymer. Both styrene and 2-vinylpyridine monomers as well as their dimers are present in the pyrogram (see also Section 6.5 for pyrolysis of poly(2-vinylpyridine)). In addition, AB types compounds are seen in the pyrogram. The spectra of 2-(3-phenylbut-3-enyl)pyridine and of 2-[1-(2-phenylethyl)vinyl]pyridine are shown in Figure 6.2.12 and 6.2.13. These spectra are not available In common mass spectral libraries (Nist 98, Wiley 275, etc.). 

Figure 6.7.29. Spectrum of 2-methyl-3-methylenehexanedioic acid dimethyl ester (from NIST 98 mass spectral library).

The spectrum of 2-methyl-2-propenoic acid dodecyl ester is available in commercial mass spectral libraries (NIST 2002, Wiley 7 and previous versions) and is shown in Figure 6.7.36. 

The current mass spectral libraries (NIST 2002, Wiley 7) do not contain the spectra of these compounds, and therefore they were not identifiable by the MS library searches. The use of mass spectrum fragments can be of help in these situations. One example is the tentative identification for the peak with retention time of 75.48 min. (from Figure 6.9.2) as 4-methyl-1 - 1 -methyl-1 -[2-methyl-5-(methylethyl)cyclohexyl]ethyl benzene. The fragment assignments for the ions seen in the mass spectrum are shown in Figure 6.9.3. 

Some of the identifications given in Table 16.1.4 are only tentative because the corresponding spectra are not available in common mass spectral libraries (NIST,... 

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