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dc.contributor.advisorHernández-Rivera, Samuel P.
dc.contributor.authorPerez-Almodovar, Luis
dc.description.abstractThe 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.en_US
dc.description.abstractLa necesidad de instrumentos y métodos de rápida respuesta para la detección e identificación de agentes químicos y biológicos en entornos de defensa y seguridad nacional se ha convertido en un tema cada vez más importante en la sociedad moderna. Muchas de las muestras recolectadas para la detección de explosivos están contenidas en matrices de suelo. Estos suelos pueden contener mezclas de materiales energéticos distribuidos de manera heterogénea. Otras muestras comunes que pueden ser objetivos para la detección de explosivos son las superficies de escombros, superficies metálicas, superficies plásticas, superficies de madera, cartón o tela. Este trabajo se centró en el desarrollo de una nueva técnica de separación e identificación mediante cromatografía de capa fina (TLC) acoplada a espectroscopia láser de infrarrojo medio (MIR). La técnica proporciona un método práctico, de bajo costo, rápido, robusto y reproducible para la separación de explosivos, seguido de identificación y cuantificación. Se llevó a cabo una comparación directa de los espectros de trinitrotolueno (TNT) adquiridos por la nueva técnica y con la técnica de reflexión total atenuada con infrarrojo de transformada de Fourier (ATR-FTIR) acoplado a TLC. Se prepararon y probaron soluciones de TNT que dieron como resultado unas masas depositadas de 0.39 - 100 µg. El método láser MIR se evaluó calculando las figuras mérito en términos de linealidad de curvas de calibración, sensibilidad y precisión. Los espectros de TNT mostraron dos bandas características del explosivo de aproximadamente 1350 cm-1 y 1550 cm-1 en comparación con los espectros adquiridos por ATR/FTIR. El límite de detección para TNT fue de 74 ng, mientras que el límite de cuantificación fue de 224 ng. Las rutinas de análisis multivariable fueron usadas para evaluar los datos espectroscópicos, encontrar las fuentes de variación y determinar cómo estos se relacionaban. Se usó análisis de regresión de mínimos cuadrados parciales (PLS) y PLS combinado con análisis discriminante (PLS-DA). Finalmente, para evaluar nuestra técnica para la detección de explosivos en el suelo, se prepararon y analizaron muestras simuladas de suelo contaminado con TNT. Los resultados demuestran que el método puede servir como una excelente plataforma para diseñar nuevos métodos analíticos útiles para la identificación y cuantificación de estos agentes químicos.en_US
dc.description.sponsorshipThis work was conducted in collaboration with the Center for Chemical Sensors and Development at the Chemistry Department of University of Puerto Rico-Mayaguez sponsored by the Department of Defense, Agreement Number W011NF-11-1-0152. This material is based upon work supported by the U.S. Department of Homeland Security, Science and Technology Directorate, Office of University Programs, under Grant Award 2013-ST-061-ED0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security. The ALERT Center of Excellence is also acknowledged for their continued support through the R3-C component. Many thanks to all the staff and the R3 Component Deputy Director, Prof. Carey Rappaport as well as the ALERT Project Director, Prof. Michael Silevitch, from Northeastern University, Boston, MA for their continued support of minority institutions.en_US
dc.subjectThin layer chromatography (TLC)en_US
dc.subjectMid-infrared laser spectroscopyen_US
dc.subjectQuantum Cascade Laser (QCL)en_US
dc.subjectTrinitrotoluene (TNT)en_US
dc.subjectpartial least squares regression (PLS)en_US
dc.subject.lcshTNT (Chemical)en_US
dc.subject.lcshThin layer chromatographyen_US
dc.subject.lcshLaser spectroscopyen_US
dc.titleSeparation, identification, and quantification of explosives using thin layer chromatography coupled to mid-infrared laser spectroscopyen_US
dc.rights.licenseAll rights reserved
dc.rights.holder(c) 2019 Luis Alberto Perez-Almodovaren_US
dc.contributor.committeeMina Camilde, Nairmen
dc.contributor.committeeRoman Velazquez, Felix
dc.contributor.representativeFernandez, Felix
dc.contributor.collegeCollege of Arts and Sciences - Sciencesen_US
dc.contributor.departmentDepartment of Chemistryen_US

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