Mass spectrometry library search

Palisade (1996) BenchTop/PBM Mass Spectrometry Library search system, http //www.sisweb.com/soJtware/ms/ benchtop.htm (accessed 10 May 2014). 

The common procedure to generate silylated pyrolysates is to perform pyrolysis in a filament system followed by off-line derivatization with BSTFA. The chromatographic separation was done on a DB-5 column (60 m long, 0.32 mm i.d., 0.25 pm film thickness) using a temperature gradient between 50° C and 300° C with detection by mass spectrometry. The compounds identified by mass spectral library search in the pyrograms from Figures 12.3.3 and 12.3.4 are listed in Table 12.3.2. 

Stein SE and Scott DR (1994) Optimization and testing of mass spectral library search algorithms for compound identification. Journal of the American Society of Mass Spectrometry 5 859-866. 

Maximum benefit from Gas Chromatography and Mass Spectrometry will be obtained if the user is aware of the information contained in the book. That is, Part I should be read to gain a practical understanding of GC/MS technology. In Part II, the reader will discover the nature of the material contained in each chapter. GC conditions for separating specific compounds are found under the appropriate chapter headings. The compounds for each GC separation are listed in order of elution, but more important, conditions that are likely to separate similar compound types are shown. Part II also contains information on derivatization, as well as on mass spectral interpretation for derivatized and underivatized compounds. Part III, combined with information from a library search, provides a list of ion masses and neutral losses for interpreting unknown compounds. The appendices in Part IV contain a wealth of information of value to the practice of GC and MS. 

If you frequently analyze pesticides, obtain the latest edition of Mass Spectrometry of Pesticides and Pollutants (Safe and Hutzinger. Boca Raton, FL, CRC Press). This book, combined with the list of most abundant ions (Table 25.1) and/or a computer library search, will be sufficient to identify most commercial pesticides. Also, see Chapters 17, 26, and 27. 

To record a mass spectrum it is necessary to introduce a sample into the ion source of a mass spectrometer, to ionize sample molecules (to obtain positive or negative ions), to separate these ions according to their mass-to-charge ratio (m/z) and to record the quantity of ions of each m/z. A computer controls all the operations and helps to process the data. It makes it possible to get any format of a spectrum, to achieve subtraction or averaging of spectra, and to carry out a library search using spectral libraries. A principal scheme of a mass spectrometer is represented in Fig. 5.2. To resolve more complex tasks (e.g., direct analysis of a mixture) tandem mass spectrometry (see below and Chapter 3) may be applied. 

Based on a new technology, particle beam enhanced liquid chromatography-mass spectrometry expands a chemist s ability to analyse a vast variety of substances. Electron impact spectra from the system are reproducible and can be searched against standard or custom libraries for positive compound identification. Chemical ionization spectra can also be produced. Simplicity is a key feature. A simple adjustment to the particle beam interface is all it takes. 

As an example of the application of gas chromatography-mass spectrometry, Fig. 1.7 shows a reconstructed chromatograph obtained for an industrial sludge. The Finnigan MAT 1020 instrument was used in this work. Of the 27 compounds searched for, 15 were found. These data were automatically quantified. This portion of the report contains the date and time at which the run was made, the sample description, who submitted the sample and the analyst, followed by the names of the compounds. If no match for a library entry was found, the component was listed as not found . Also shown is the method of quantification and the area of the peak (height could also have been chosen). 

Qian, K. Killinger, W.E. Casey, M. Nicol, G.R. Rapid Polymer Identification by In-Source Direct Pyrolysis Mass Spectrometry and Library Searching Techniques. Anal. Chem. 1996, 68, 1019-1027. 

For those readers who are not yet familiar with mass spectrometry, the introduction provides an explanation of the basics of mass spectrometry and its instrumentation as well as practical aspects and applications in bioanalysis. Next, a block of three chapters shows different affinity selection procedures suitable to identify hits from combinatorial compound libraries. This subject, being metaphorically speaking a search for a needle in a haystack, is of outstanding relevance for big pharma . The techniques described here offer real high throughput capabilities and are implemented already in the routine industrial screening... 

Gros M, Petrovic M, Barcelo D (2009) Tracing pharmaceutical residues of different therapeutic classes in environmental waters by using liquid chromatography/quadmpole-linear ion trap mass spectrometry and automated library searching. Anal Chem 81 898-912... 

In the past, PTRC screening was mainly based on gas chromatography-mass spectrometry (GC-MS) [116]. The choice of GC-MS was based on a number of good reasons (separation power of GC, selectivity of detection offered by MS, inherent simplicity of information contained in a mass spectrum, availability of a well established and standardized ionization technique, electron ionization, which allowed the construction of large databases of reference mass spectra, fast and reliable computer aided identification based on library search) that largely counterbalanced the pitfalls of GC separation, i.e., the need to isolate analytes from the aqueous substrate and to derivatize polar compounds [117]. 

Gas Chromatography-Mass Spectrometry. A Finnigan 4500/Incos instrument with a 30-m X 0.32-mm i.d. capillary column coated with SP-B-5 was used. The GC parameters were as follows injector, 270 °C column oven temperature programmed, 50 °C (0.1 min, hold) 15 °C/min to 100 °C, 5 °C/min to 270 °C internal standard, anthracene-djo helium flow, 3.0 mL/min sample size, 3.0 /xL. MS conditions were as follows El, 70 eV scan (m/z), 35-650 daltons source temperature, 250 °C filament current, 0.5 A sensitivity, 10-8 A/V. (NOTE When the name of a compound is followed by (confirmed) , it means that the standard material was analyzed for confirmation under conditions identical to those of the sample when the name is followed by (tentative) , it means that the mass fragmentography showed the best fit (>80 ) based on the National Bureau of Standards [NBS] library computer search.)... 

Modem mass spectral databases allow the automated searching of very extensive mass spectral libraries.6 This has made the identification of compounds by mass spectrometry a far more straightforward task. One must understand, however, that such databases are no substitute for the careful analysis of each mass spectrum and that the results of database matchup are merely suggestions. 

To many, mass spectrometry is synonymous with El mass spectrometry. This view is understandable for two reasons. First, historically, El was universally available before other ionization methods were developed. Much of the early work was El mass spectrometry. Second, the major libraries and databases of mass spectral data, which are relied upon so heavily and cited so often, are of El mass spectra. Some of the readily accesible databases contain El mass spectra of over 390,000 compounds and they are easily searched by efficient computer algorithms. The uniqueness of the El mass spectrum for a given organic compound, even for stereoisomers, is an almost certainty. This uniqueness, coupled with the great sensitivity of the method, is... 

Although individual laboratories find it useful to compile their own reference library files, access to very large collections of mass spectra and to published data [55] is essential. A compilation of many thousands of spectra by the Aldermaston Mass Spectrometry Data Centre and the Division of Computer Research and Technology at the National Institutes of Health [56-58] has been made available commercially. The file can be searched in a number of ways using an interactive conversational mass spectral search system via a teletype and acoustic link over telephone lines. 

Identification of an intoxicating agent and its metabolites in post-mortem plasma and urine was described by Verheij et al. [27] by combining accurate mass determination with high resolution mass spectrometry in on-line LC-MS, El, and Cl spectra of the various peaks, library searching of the El spectra, and information from the LC retention times. 

In the modern analytical laboratory, gas chromatography-mass spectrometry (GC-MS) is a vital tool in the characterization and identification of unknowns. The advantages of GC-MS are accuracy in quantitation, low detection limits, tentative identification of unknowns by spectral library search, and a high degree of reliability and versatility ( 1). Of all the chemicals known, however, only a fraction (=20 ) are amenable to analysis by GO. The remaining compounds, because of their high molecular weight, thermal instability, or ionic and/or polar character, are not suited to direct GC determination. 

Sanders, M. Josephs, J., Schwartz, J. Tymiak, A. DiDonato, G. Rapid Identification of Natural Products Using a Modified Ion Trap Mass Spectrometer and MS/MS Spectral Library Searching, in Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, Texas, June 13-17, 1999. 

D. High Throughput MSn Library Search in Natural Product Research, in Proceedings ofthe 51st ASMS Conference on Mass Spectrometry and Allied Topics, Quebec, Canada, June 8-12, 2003. 

Josephs, J.L. Sanders, M. DiDonato, G. Hail, M. Kerns, E. Volk, K. Lee, M.S. Automated LC/MS/MS and CID Spectral Library Searching of Pharmaceutical Impurilios Using Ion Traps and Triple Quads, in Proceedings of the 45th ASMS Conference on Mass Spectrometry and Allied Topics, Palm Springs, CA, 1997. 

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