Aplicações de análises térmicas em fraude de alimentos e estudo de pré-formulação farmacêutica

Abstract

The thermal analysis techniques such as Differential Scanning Calorimetry (DSC), Thermogravimetry (TG) and Differential Thermal Analysis (DTA) are well-known techniques used in the physical-chemical characterization of different materials. The present work describes two different applications of thermal analysis: fraud in food and pharmaceutical pre-formulation study. In the first application, in food fraud, the study of the detection of coffee adulteration by corn was carried out. The adulteration of ground coffee has the purpose of generate higher profits, but also affects tis quality and changes its nutritional properties. In this case the adulteration of coffee by corn was detected and quantified using DSC and Infrared Spectroscopy coupled to PCA (Principal Component Analysis) and PLS (Partial Least Squares) models. The level of adulteration used was between 0.5 to 40% (w/w). The PCA models were able to differentiate adulterated samples from unadulterated ones, even at levels lower than 1% (w/w) of adulterant. PLS models showed a good correlation between predicted and reference values, with RMSECV (Root Mean Square Error of Cross-Validation) lower than 3.5% for the model constructed with DSC data, and 2.7% for the model with infrared spectroscopy data. The second application involves pharmaceutical preformulation studies with the drugs amlodipine besylate and olmesartan medoxomil. Both of drugs are antihypertensives that can be administrated alone, in monotherapy, or in pharmaceutical association. In the development of a new drug is required knowledge of the physicochemical properties of the drug and excipients involved, and the formulation stability, so that the new product does not have properties and characteristics change over time, guaranteeing the safety, efficiency and product quality. At first, DSC data were used to determine the thermokinetic and thermodynamic parameters of the drugs and to perform the drug-excipient compatibility study by analyzing binary mixtures of the drugs and excipients 1:1 (w/w). Binary mixtures of drugs and excipients 1:1 (w/w), and ternary mixtures containing the drugs amlodipine and olmesartan, and excipients 1:1:1 (w/w/w) were analyzed by FTIR with heating. Binary mixtures of each drug with excipient in a proportion of 1:1 (w/w), and ternary mixtures, containing drugs: amlodipine besylate and olmesartan medoxomil, and excipients in a proportion of 1:4:5 (w/w/w), were analyzed by HPLC (High Performance Liquid Chromatography) immediately after preparation and after being stored in stability chamber at 40±1 ºC and 75±5% of relative humity (RH) for 3 and 6 months, and at 40±1 ºC and dry conditions for 3 and 6 months, in order to compare the results obtained by DSC and FTIR. The excipients tested were pregelatinized starch, cellulose, croscarmellose sodium, magnesium stearate, polyvinyl alcohol, titanium dioxide, talc, polyvinylpyrrolidone, lactose and polyethylene glycol. According to the results obtained by DSC, FTIR with heating and HPLC it was possible to observe that the storage conditions are crucial for the stability of the formulation. In all cases, amlodipine proved to be incompatible with starch, olmesartan with PVP and lactose, and the pharmaceutical association with starch, cellulose, croscarmellose sodium, magnesium stearate, polyvinyl alcohol, PVP, lactose and PEG.