Perez Almodovar, Luis

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    Separation, identification, and quantification of explosives using thin layer chromatography coupled to mid-infrared laser spectroscopy
    (2019-05-10) Perez Almodovar, Luis; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Mina Camilde, Nairmen; Román Velázquez, Félix R.; Department of Chemistry; Fernández, Félix E.
    The need for rapid instrumentation and methods for detection and identification of chemical and biological threat agents in national defense and homeland security settings has become an ever more important issue in modern society. Many of the samples collected for the sensing of explosives are contained in soil matrices. Soils from these media can contain mixtures of energetic compounds distributed heterogeneously. Other common samples that can be targeted for detection of explosives are debris surfaces; these surfaces can be metallic, plastic, wood, cardboard, fabric, etc. This work focused on the development of a new separation and identification technique using thin layer chromatography (TLC) hyphenated to mid-infrared (MIR) laser spectroscopy. The technique provides a practical, low cost, fast, robust, and reproducible method for screening of explosives, followed by identification and quantification. Direct comparison of trinitrotoluene (TNT) spectra acquired by the new hyphenated technique and with Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) coupled to TLC was carried out. TNT solutions in a 0.39 – 100 µg of deposited mass were prepared and tested. The MIR laser method was evaluated by calculating the analytical figures of merit in terms of linearity of calibration curves, sensitivity, and precision. TNT spectra showed two characteristic bands of the explosive about 1350 and 1550 cm-1 when compared to spectra acquired by ATR-FTIR. The detection limit for TNT was 74 ng while the quantification limit was 224 ng. Multivariate analysis routines evaluated the spectroscopic data to find the sources of variation and determine how they were related. Partial least squares (PLS) regression analysis and PLS combined with discriminant analysis (PLS-DA) was used. Finally, to evaluate our hyphenated technique for detection of explosives in soil, simulated contamination samples of TNT in soil were prepared and analyzed successfully. Experiments demonstrated that the method could serve as an excellent platform to devise analytical methods useful for the identification and quantification of chemical targets.