Villanueva López, Vladimir

Profile Picture

Filters

20211
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    Publication
    Development of sensitive analytical methods based on quantum cascade laser spectroscopy
    (2021-07-09) Villanueva López, Vladimir; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Guzmán Martínez, Aikomari; Mina Camilde, Nairmen; Santana Vargas, Alberto; Department of Chemistry; Rodríguez Román, Daniel
    Quantum cascade laser (QCL) technology has enabled the development of more sensitive analytical methods based on mid-infrared spectroscopy due to high brightness and spectral resolution. The advantages of this technology have been proved in material characterization. Still, it is necessary to gather a more profound knowledge of its capability through practical applications to exploit at the maximum level its numerous advantages. This dissertation provides a framework on how to develop analytical methods based on QCL from the development of software based on LabVIEW to acquire spectroscopic data, process the signals, and finally the analysis of the spectroscopic data using multivariate analysis (MVA) methods and machine learning (ML) algorithms. The angle of incidence is an important factor that significantly affects reflectance measurements. The effect of the changes in this critical parameter was evaluated. First, experiments performed at a near-grazing angle of incidence enable reflection-absorption infrared spectroscopy (RAIRS). Under that configuration, detecting analytes at trace levels, such as high explosives (HEs), including PETN, RDX, and Tetryl, was successful. The quantification of C-4 was achieved using partial least square regression (PLS) analysis. Then the experiments changing the angle of incidence and the substrate where the HEs were deposited were conducted to evaluate the capabilities of advanced machine learning algorithms to classify them. The Naive Bayes classifier showed the highest discriminating capabilities with a 96.9% probability of detection and 93.3% precision. The detection of HEM was successful. Finally, diffuse reflectance measurements in back-reflection mode, with laser beam incidence parallel to surface normal, were conducted to develop an analytical method for quantifying active pharmaceutical ingredients (APIs) in tablets and powder mixes with excipients. This optical configuration allows deeper penetration in compressed tablets. Therefore, larger volumes of the analyte can be scrutinized. The experimental studies were focused on the analysis of condensed phases, but they can be extended to gas-phase/vapors sensing due to the high spectral resolution of QCL.