Citation:

Scott, D. EXPERT SYSTEM FOR ESTIMATING MOLECULAR WEIGHTS OF VOLATILE ORGANIC COMPOUNDS FROM LOW RESOLUTION MASS SPECTRA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-91/207 (NTIS PB91242990), 1991.

Description:

MAXMASS, the highest mass with an intensity of 5% of the base peak in a low resolution mass spectrum, has been found to be linearly correlated with the true molecular weights of 400 randomly selected spectra, yielding a family of parallel lines. imple exert system using MAXMASS has been developed to estimate molecular weights of unknown volatile compounds from their mass spectra. his is a empirical rule-based system which will run on a personal computer. t consists of a classification module chained to separate molecular weight prediction modules for six classes. hese are benzenes; chlorobenzenes bromoalkenes/alkenes; mono- and dichloroalkanes/alkenes; tri-,tetra- and pentachloro-alkanes/alkenes; and unknown (other) classes. he rules were derived from: ational Institute of Standards and Technology (NIST) reference spectra of 75 target toxic compounds from the first five classes and 32 from the unknown class. erformance tests of molecular weight predictions were made with the expert system and the Self Training Interpretive and Retrieval System (STIRS) on NIST reference spectra of the 107 training compounds; on a set of 32 test NIST reference spectra of other compounds found in air samples; on a set of 100 randomly selected NIST reference spectra; and on 30 spectra taken from actual field gas chromatography/mass spectrometry samples. he expert system performed much better than STIR on training spectra, STIR performed better on test and random spectra, and the expert system performed better with field data.

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