Arrays of Sensors and Microsensors for Field Screening of Unknown Chemical Wastes.
Penrose-WR; Stetter-JR; Findlay-MW; Buttner-WJ; Cao-Z
NIOSH 1991 Feb:85-93
A sensor was developed which can identify chlorinated or brominated compounds in the vapor phase or, with the use of a permeable membrane, in dissolved form. A combination of catalytic pyrolysis and electrochemical detection can be used to distinguish unknown compounds with a modest degree of selectivity that may be enough to be useful in many field applications. An array of electrochemical gas sensors with different but overlapping selectivities was used for pyrolysis-EC. Grain samples were heated to 60 degrees-C and flushed with air to generate grain odor samples. Gas samples were produced by injecting measured volumes of test compounds as liquids into gas bags. Pyrolysis and electrochemical detection data, combined with k-nearest neighbor and neural network classification methods had been successfully and effectively used for such varied tasks as to classify stored grains by odor, or to classify waste chemicals by functional group. The neural net can be made to adapt dynamically to instrument drift and it adjusts through experienced gained in use. The errors which are made in classification correspond in a general sense to errors made by human experts faced with similar problems and ambiguities in data. Two applications were discussed, the rapid identification of chemical vapors and the grading of grain according to odor.
Chemical-analysis; Analytical-methods; Environmental-pollution; Halogenated-hydrocarbons; Food-contaminants; Sampling-methods; Chemical-composition; Screening-methods;
Field Screening Methods for Hazardous Wastes and Toxic Chemicals. Second International Symposium, February 12-14, 1991. Sponsored by U.S. EPA; U.S. DOE; U.S. Army Toxic and Hazardous Materials Agency; U.S. Army Chemical Research Development and Engineering Center; U.S.A.F.; Florida State Univ.; National Environmental Technology Applications Corp.; and NIOSH