A program for the Identification of the principal components of mixtures through interpretation of the infrared mixture spectrum (lnt IRpret) was developed. Thls program, which was developed as a preiimlnary Screening tool for unknown organics handled on hazardous waste remedial action sites, has five maln subroutlnes: the interferogram processing and peak selection Subroutine (PUSHSUB), the automated knowledge acquisition subroutlne (AUTOGEN), the system optlmlzatlon subroutine (STO), the interpretation subroutine (PAIRS), and the final processing subroutine to subtract spectral simliarlty (PAIRSPLUS). Prlnclpal advantages of this system compared to those previously reported are speed, fiexlblilty, and accuracy. For a training set of 62 pure compounds and a data set of 67 four-component mixtures requiring 4154 decisions, the system correctly Identified 216 true posltlve results and 3840 true negatlves and Incorrectly identlfled 46 false posltlvies (19.4%) and 52 false negatives (1.2%).In order to satisfy the requirements of hazardous waste analysis a t Superfund and a t licensed disposal sites (I+), a program for automated waste mixture identification (PAWMI) through the interpretation of the infrared (IR) spectrum of the waste mixture was developed (7, 8) and tested on hazardous waste drum samples (9). This approach, which utilizes the speed and sensitivity of Fourier transform infrared (FT-IR) spectrometry meets many of the requirements of a near real-time, principal component screening technique for organic hazardous waste samples ( I ) .Two limitations of PAWMI were that once a training set, consisting of a library of reference of spectra, was defined, the rules for the inference engine (PAIRS) (10-16) had to be generated manually. The second limitation was that the PAWMI compound identification software only uses peak location information.An approach to the automated generation of functional group interpretation rules for PAIRS was previously developed (1 7). This system defines a value "occurrencen as the "number of peaks in a given wavenumber range divided by the number of compounds in the database containing the functionality of interest". This value was used to weight peak position information for the generation of expectation values for the presence of certain functional groups. Efforts by other investigators have been successful in the interpretation of IR spectra by using computerized inter-' Present address: . pretation or matching procedures. These program systems include the hierarchal tree (18) and table-driven (19) programs developed by Munk et al. and the pattern recognition approach of Frankel (20). These systems were primarily aimed a t identifying functional groups in compounds, as was the original PAIRS program. The success of these approaches were a function of the data set and functional group studied. A related work aimed primarily a t identifying compounds in mixtures was that of Lowry (21) which used a Boolean logic based search system. Many of these approaches owe their origins to ear...