Jerez Rozo, Jackeline I.

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2007 - 200912010 - 20131
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    Enhanced Raman Scattering of TNT on nanoparticles substrates: Ag, Au and Au/Ag Bimetallic colloids prepared by reduction with sodium citrate and hydroxylamine hydrochloride
    (2007) Jerez Rozo, Jackeline I.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Castro Rosario, Miguel E.; Mina Camilde, Nairmen; Department of Chemistry; Narinder, Mehta
    Surface-Enhanced Raman Scattering (SERS) provides extremely high sensitivity, due to increase in the Raman cross-sections of intrinsically very weak scattering events making these events comparable or even better than photon emission efficiencies found in fluorescence processes. The observation of vibrational spectra of adsorbed species on surfaces by SERS is one of the most incisive analytical methods for chemical and biochemical detection and analysis. The metallic nanoparticles that make SERS possible are of fundamental interest since they possess unique size-dependent properties (optical, electrical, mechanical, chemical, magnetic, etc.). These properties are quite different from the bulk and the atomic state. Bimetallic nanoparticles are of particular interest since they combine the advantages of the individual monometallic counterparts. Metal colloids have become the most commonly used nanostructures for SERS. Gold, silver and Ag/Au bimetallic alloys colloids have been synthesized by chemical reduction methods and have been used for detecting TNT in solution with high sensitivity and high molecular specificity. The study focused on metallic nanoparticles within size range in the 50-100 nm. The nanoparticles were characterized using UV-VIS spectroscopy, Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Raman Spectroscopy. The detection of TNT was conducted via an indirect method that involved the alkaline hydrolysis of TNT in presence of a strong base (NaOH). This method offers the advantage of generating reaction products that provided enhanced detection in the presence of roughened surfaces (SERS). The detection of TNT degradation products was evaluated on gold, silver and silver/gold bimetallic colloids using excitation wavelengths of 785 and 532 nm. The results revealed an increase in the intensity of the vibrational signals, attributed to the SERS spectra of degradation products that resulted from the alkaline hydrolysis of TNT. Bands associated to NO2 out-of-plane bending modes at ca. 820 and 850 cm-1 and NO2 stretching modes at 1300-1370 cm-1 were detected.
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    Development of a methodology to determine drug distribution in polymeric thin film formulations using hyperspectral image analysis
    (2013) Jerez Rozo, Jackeline I.; Romañach Suárez, Rodolfo J.; College of Arts and Sciences - Sciences; Torres Candelaria, Jessica; Acevedo Rullán, Aldo; Perales Pérez, Oscar J.; Department of Chemistry; Sundaram, Paul A.
    This dissertation is focused on the development of analytical methods to determine drug distribution throughout polymeric films using hyperspectral image analysis. The NIR-CI and Raman mapping techniques have been used to analyze the distribution and quantification of drug in a novel pharmaceutical formulation. This pharmaceutical formulation was developed with the goal of maintaining the drug with a specific particle size in a non agglomerated form and to satisfy two commonly encountered pharmaceutical needs: enhanced dissolution rate of poorly soluble drugs and the content uniformity of drugs administered in low doses. In these films, the active ingredient is a poorly soluble drug, which is dispersed in the polymer and additionally; surfactant and lubricant are added. The water poorly soluble drugs have to be uniformly distributed in a film formulation to have an acceptable drug content uniformity. This is the reason why drug distribution is an important factor in these type of pharmaceutical formulations. In order to obtain the desired distribution it is necessary to find those areas of the film where the drug is agglomerated, and use this information to improve the process. Chapter 3 presents the results of the first methodology developed. The first methodology was based on determining the pixels of maximum intensity value at 2080 nm. At this wavelength, pixels with positive values correspond to the drug. A film with large agglomerates was used to develop this methodology. Results show that the drug should be highly agglomerated to find pixels of pure drug. Therefore, the methodology was developed to evaluate the distribution of those pixels that are composed mainly of drug but also containing others components. Agglomerations of these pixels are called drug rich areas in this dissertation. The procedure followed to evaluate these drug rich areas is: to Identify of drug rich areas, observe the distribution of drug rich areas throughout the film surface, and do a visual comparison between different areas or films. This methodology was applied in the images analysis of the chapter 5-7. Chapter 4 compares the previously developed methodology with a new approach using Multivariate Image Analysis (MIA). The previously developed methodology is based on observing the distribution of drug rich areas at 2080 nm. The new methodology is based on the Bharati and MacGregor approach for incorporating the textural information of the image. MIA was used to explore the spectral and spatial relationship between the API and the different excipients. Results obtained with the two methodologies are comparable in terms of drug distribution. Chapters 5 -7 show the results obtained by applying the methodologies developed. These results are based on analysis of high intensity values at 2080 nm and score images. Nanosuspensions produced from wet stirred media milling (WSMM) were used to prepare these polymeric films. In these chapters the effect of stabilizers on controlling growth and agglomeration of the drug, the influence of the drug molecule on the distribution of drug rich areas and the impact of the drying process in the agglomeration of these drug rich areas, were evaluated. Chapter 8 shows the results obtained during the internship. The objective of this internship was to develop skills in solving challenging problems in both fundamental and applied research. This internship was conducted in a Pharmaceutical Chemical Plant during a period of 8 months. During this time, two NIR methods were developed in an effort by the Pharmaceutical Chemical Plant to implement techniques of analysis faster and cost effective. A feasibility study using Raman Spectroscopy for the ID of raw materials also was completed. Chapter 9 summarizes the scientific contribution of this dissertation.