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Baptistao M.,University of Campinas | Rocha W.F.D.C.,National Institute of Metrology of Brazil | Poppi R.J.,University of Campinas | Poppi R.J.,National Institute of Science and Technology INCT for Bioanalytics
Journal of Molecular Structure | Year: 2011

In this work, it was used imaging spectroscopy and chemometric tools for the development and analysis of paracetamol and excipients in pharmaceutical formulations. It was also built concentration maps to study the distribution of the drug in the tablets surface. Multivariate models based on PLS regression were developed for paracetamol and excipients concentrations prediction. For the construction of the models it was used 31 samples in the tablet form containing the active principle in a concentration range of 30.0-90.0% (w/w) and errors below to 5% were obtained for validation samples. Finally, the study of the distribution in the drug was performed through the distribution maps of concentration of active principle and excipients. The analysis of maps showed the complementarity between the active principle and excipients in the tablets. The region with a high concentration of a constituent must have, necessarily, absence or low concentration of the other one. Thus, an alternative method for the paracetamol drug quality monitoring is presented. © 2011 Elsevier B.V. All rights reserved. Source


Rocha W.F.D.C.,University of Campinas | Rocha W.F.D.C.,National Institute of Metrology of Brazil | Poppi R.J.,University of Campinas | Poppi R.J.,National Institute of Science and Technology INCT for Bioanalytics
Analytica Chimica Acta | Year: 2011

Raman spectroscopy and control charts based on the net analyte signal (NAS) were applied to polymorphic characterization of carbamazepine. Carbamazepine presents four polymorphic forms: I-IV (dihydrate). X-ray powder diffraction was used as a reference technique. The control charts were built generating three charts: the NAS chart that corresponds to the analyte of interest (form III in this case), the interference chart that corresponds to the contribution of other compounds in the sample and the residual chart that corresponds to nonsystematic variations. For each chart, statistical limits were developed using samples within the quality specifications. It was possible to identify the different polymorphic forms of carbamazepine present in pharmaceutical formulations. Thus, an alternative method for the quality monitoring of the carbamazepine polymorphic forms after the crystallization process is presented. © 2011 Elsevier B.V. Source


Muller A.L.H.,Federal University of Santa Maria | Muller A.L.H.,National Institute of Science and Technology INCT for Bioanalytics | Muller C.C.,Federal University of Santa Maria | Muller C.C.,National Institute of Science and Technology INCT for Bioanalytics | And 9 more authors.
Analytical Letters | Year: 2012

A microwave-induced combustion (MIC) method was applied for cigarette tobacco digestion and further determination of bromide (Br), chloride (Cl), and fluoride (F) by ion chromatography (IC). Samples (up to 500 mg) were combusted at 20 bar of oxygen. Combustion was complete in less than 30 s, and analytes were absorbed in (NH4)2CO3 solutions. A reflux step, not available in other systems, was applied to improve analyte absorption. Absorbing solution with 50 mmol L-1(NH4)2CO3 was selected because it showed recovery close to 100% for samples containing spikes of halogens. Accuracy of the proposed procedure was evaluated by analysis of certified reference materials and the agreement was better than 97% for all analytes using 50 mmol L-1 (NH4)2CO3 as absorbing solution and 5 min of reflux. Temperature during combustion was higher than 1400°C and the residual carbon content was always lower than 1%. With the use of the MIC system, up to eight samples could be processed simultaneously, and a single absorbing solution was suitable for all analytes. Limits of quantification by MIC and further IC determination were 0.50, 0.20, and 0.10 μg g-1 for Br, Cl, and F, respectively. © 2012 Copyright Taylor and Francis Group, LLC. Source

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