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Similarity index , mass spectra

For an unknown mass spectrum (A), in this case of a component (known to be 2-hydroxyxanthone) extracted from a plant, the system retrieves from a library of 39,000 reference spectra five references having a similarity index (SI) value of at least 5 per cent (as compared with spectrum A). First on the hit list is 2-hydroxyxanthone,of which the reference spectrum (B) has an Sl-value of 69.2 per cent. References 2,3 and 4 are isomers, of which the mass spectra are expected (on mass spectrometric grounds) to show much similarity with that of 2-hydroxyxanthone. Reference 5 is a different compound, which, however, has some structural featinres in common with hydroxy-xanthones. As to the Sl-values only an exact copy of a reference spectrum 3delds an SI value of 100 per cent. Two different spectra of a compoimd, recorded under different experimental conditions, however, will always exhibit systematic differences, which in some cases may be qxiite substantial. The similarity index used in this library search system takes account of such differences. ... [Pg.224]

Fragmentation of these compounds are also similar. Therefore assignment of the individual component requires additional information, linear retention index or Kovat s index and confirmation with authentic standards. Manual interpretation of the mass spectrum is some time needed, when there is no fitted matching. Isotope abundance is very useful to postulate the identity of molecule or fragment. [Pg.273]

Fig. 4. Mass spectrum of the peak with the retention time of 10.72 min. From the NIST library search, the compoimd was matched with 2-phenylethanol (phenylethyl alcohol) with 932 similar index (SI). Fig. 4. Mass spectrum of the peak with the retention time of 10.72 min. From the NIST library search, the compoimd was matched with 2-phenylethanol (phenylethyl alcohol) with 932 similar index (SI).

See other pages where Similarity index , mass spectra is mentioned: [Pg.84]    [Pg.765]    [Pg.201]    [Pg.274]    [Pg.812]    [Pg.203]    [Pg.159]    [Pg.191]    [Pg.149]    [Pg.189]    [Pg.259]    [Pg.757]    [Pg.197]    [Pg.237]    [Pg.214]    [Pg.169]    [Pg.404]   
See also in sourсe #XX -- [ Pg.680 ]




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