Record Display for the EPA National Library Catalog

RECORD NUMBER: 32 OF 37

OLS Field Name OLS Field Data
Main Title Preprocessing, Variable Selection, and Classification Rules in the Application of SIMCA Pattern Recognition to Mass Spectral Data.
Author Dunn, W. J. ; Emery, S. L. ; Graham Glen, W. ; Scott, D. R. ;
CORP Author Illinois Univ. at Chicago Circle.;Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Research and Exposure Assessment Lab.
Publisher c1989
Year Published 1989
Report Number EPA/600/J-89/316;
Stock Number PB90-198722
Additional Subjects Organic compounds ; Computerized simulation ; Pattern recognition ; Gas chromatography ; Mass spectroscopy ; Calibrating ; Performance evaluation ; Reprints ; Air pollution detection ; Toxic substances
Holdings
Library Call Number Additional Info Location Last
Modified
Checkout
Status
NTIS  PB90-198722 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. NTIS 08/27/1990
Collation 9p
Abstract
In a recent report a strategy was proposed for the classification and identification of toxic organic compounds observed in ambient air from mass spectra using computational pattern recognition based on SIMCA principal components modeling of the autocorrelation transformed mass spectra. With this technique very good classification and identification results (87% and 84%, respectively) were obtained with GC/MS from training and calibration data for the 78 toxic compounds targeted for routine monitoring in ambient air. However, when applied to GC/MS ambient air field data, a number of hydrocarbons were incorrectly classified as chlorocarbons indicating that the training sets were not optimal for discriminating between these classes. A new strategy for data reprocessing, variable selection and class model optimization has been developed to solve this problem. Only the sixteen most intense ions in each mass spectrum are retained. The MS data are scaled by taking the square root of the intensities and the autocorrelation transform is then taken. A training class has been introduced for hydrocarbons in addition to three other classes. The original SIMCA classification rule has been modified to give a more reasonable approximation of the training set pattern structure and object distances from the class models. (Copyright (c) 1989 American Chemical Society.)