Vacuum ultraviolet (VUV) absorption spectrometer for gas chromatography (GC) is useful for universal detection of chemical compounds for quantitative analysis and qualitative identification. It offers advantages over GC-IR in detection limits (&lt; 1ppm) and over GC-MS in identification of isomers. This study focuses on the utility of time-dependent density functional theory (TD-DFT) in predicting excited states and generating theoretical VUV spectra that is in good agreement with the experimental. The degree of matching is compared in terms of peak positions, relative intensities, and general spectral shapes. The performance of the model is evaluated using several groups of isomeric compounds from different functional group classes (e.g. alcohols, aldehydes, esters, acids, glycol ethers, amines, thiols, sulfides, chlorinated organics). Since availability of experimental synchrotron data and reference compounds is limited, this computational modeling approach can aid in (a) identification of an unknown isomer, by-product, or impurity, (b) selection of spectral filter range for optimal selectivity of separation, and (c) deconvolution of overlapping peaks.

TD-DFT Performance for modeling GC-VUV absorption spectra

254th National Meeting (2017)

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