Academic literature on the topic 'FTIR-spectroscopy'

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>Diversas propriedades físico-químicas de gasolinas (teores de álcool, benzeno, aromáticos, saturados e olefinas, densidade, MON, RON e temperaturas de destilação) foram estimadas simultaneamente por espectroscopia na região do infravermelho médio (FTIR) acoplada à regressão por mínimos quadrados parciais (PLS). Os métodos de referência utilizados incluíram métodos ASTM, ABNT e o equipamento IROX, baseado em espectroscopia na região do infravermelho próximo. Embora o erro médio da predição (RMSEP) tenha sido o principal parâmetro considerado para selecionar o melhor modelo de predição para cada propriedade, a repetibilidade e a reprodutibilidade também foram avaliados. As propriedades que tiveram como método de referência o equipamento IROX (todos os teores, MON e RON) apresentaram, em geral, resultados mais pobres, sendo o pior resultado o encontrado para o teor de olefinas (21,3 +- 2,4) e o melhor para MON (82,5 +- 0,5). No caso das propriedades que tiveram como referência métodos ASTM ou ABNT (teor de álcool, densidade e temperaturas de destilação) o pior resultado encontrado foi para o teor de álcool (23,9 +- 0,7) e o melhor para a densidade (0,7556 +- 0,0025). No entanto, mesmo quando os valores de RMSEP encontrados através da regressão PLS foram considerados pequenos, os coeficientes de correlação (R2) entre os valores preditos e os de referência, para um conjunto de amostras independentes da calibração, foram menores que 0,70, para todas as propriedades. Isso se deve, principalmente, a pouca variação nos valores de algumas propriedades, como MON, por exemplo, que em todas as gasolinas analisadas apresentou valores entre 81,4 e 83,8. Ainda assim, o método FTIR-PLS mostrou-se bastante promissor como uma alternativa para a análise de gasolinas, podendo ser melhorado com a utilização de maior número de amostras de calibração e/ou com a utilização de um conjunto de amostras mais representativo, além da utilização de métodos de referência padrão.<br>Several gasoline properties (alcohol, benzene, aromatics, saturated and olefin contents, density, MON, RON and distillation temperatures) have been predicted simultaneously by spectroscopy in the region of the mid infrared (FTIR) and partial least squares regression (PLS). The methods used as reference have included ASTM and ABNT methods and the IROX equipment, based on spectroscopy in the region of the near infrared. Although the standard error of the prediction (RMSEP) has been the main considered parameter to select the best model of prediction for each property, the repeatability and the reproducibility have also been evaluated. In general, the properties determined by IROX as the reference method (all the constituents, MON and RON) have presented poor results, the worst one found being the olefins content (21,3 +- 2,4) and the best one MON (82,5 +- 0,5). In the case of the properties that had ASTM or ABNT methods as reference (alcohol content, density and distillation temperatures) the worst results were found for the alcohol content (23,9 +- 0,7) and the best one for the density (0,7556 +- 0,0025). However, even values of RMSEP found by PLS regression had been considered small, the correlation coefficients (R2) between the predicted values and reference values, for a set of samples independent of the calibration, have been shown to be below 0,70, for all the properties. This fact can be explained by the small variation in the values of some properties, as MON, that in all gasoline samples presented values between 81,4 and 83,8. FTIR-PLS method revealed promising as an alternative for gasoline analysis. This method could be improved with the use of a greater set of calibration samples and/or with the use of a more representative sample set, beyond the use of standard reference methods.

The preparation of solid dispersions, in this study felodipine/polyvinyl pyrrolidone solid dispersion, is a multifaceted phenomenon. In order to understand the formation of solid dispersions two different mixed solvent system, three different temperatures and different drug loadings were selected and monitored in real time using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy. 50 mul of the prepared solution was placed onto a pre-heated ATR crystal. The effect of PVP/API ratio, molecular interactions and effect of temperature (30&deg;C, 40&deg;C and 50&deg;C) on the rate of film formation (solid dispersions) was evaluated. The changes in the peak positions, peak intensities and peak width as a function of time was monitored. The data were then analysed using peak height measurements, statistical and chemometric data analytical tools. It was shown that the nature of the solvent, the working temperature, presence of polymer and low drug loading was found to influence the rate of evaporation of solvent, molecular interactions and quality of the final product. Moreover, using thermogravimetric techniques it was complemented that the residual solvent within the systems was within the studied limits. The spatial arrangement or distribution of components within solid dispersion was found to influence the physical stability, phase behaviour, dissolution and bioavailability. Mid infrared spectroscopic imaging has been shown to be useful and has provided unique insights in to various fields. However, it has very limited applications in analysing the pharmaceutical materials. This work aims to evaluate various image processing tools in extracting process related information. Three model systems with varying chemical composition were selected. The chemical images from the regions of interest were collected using a Varian 620 FTIR Imaging instrument equipped with 64 x 64 MCT-Focal Plane Array (FPA) detector. Firstly we showed the impact of optical artefacts on the quality of the acquired image. The data was then pre-processed to remove baseline effects, pathlength variations and image processed to extract distribution maps. Agreement between the data generated using peak height measurements, compare correlation, principal component analysis and multivariate curve resolution was obtained only with the simple systems, the advantage with the latter being that the supervised and unsupervised chemometric approaches do not require any prior information about the sample and does not suffer from any physical or chemical interferences. The success of MCR-ALS over compare correlation and PCA methods is that it does not require any pure materials library and provides chemical information respectively. Moreover, implementation and data extraction is easy using MCR-ALS. It was then showed that once the optical artefacts are separated and chemically significant information is extracted, the benefits of infrared imaging was multitude. The optimised procedures were then applied to other samples to expand the applications of mid infrared imaging. There is no established paper to date describing the application of FTIR imaging to study the solvent induced phase separation in solid dispersions. One of the aims of this work is to study the impact of two different solvents on the phase behaviour of felodipine/polyvinyl pyrrolidone solid dispersions cast from different binary solvent systems. The temperature induced phase separation and degradation have been studied using differential scanning calorimetry, scanning electron microscopy, thermogravimetric etc, however we have shown the application of FTIR imaging in assessing the temperature induced degradation complemented and supported by in situ ATR-FTIR spectroscopy and thermogravimetric analysis.