Jerusa S. Garcia

Compatibility of sildenafil citrate and pharmaceutical excipients by thermal analysis and LC–UV

The evaluation of sildenafil citrate (SC), the best-selling drug for treatment of impotence, for compatibility with various excipients was investigated using thermal and isothermal stress testing. Differential scanning calorimetry (DSC), hot-stage microscopy (HSM) and liquid chromatography (LC) with ultraviolet detection were successfully employed to investigate the compatibility between SC and various excipients commonly used in solid form in the pharmaceutical industry. The studies were performed using 1:1 (m/m) drug/excipient physical mixtures and samples were stored under accelerated stability conditions (40xa0°C at 75% relative humidity). All excipients tested (such as colloidal silicon dioxide, croscarmellose sodium, lactose, mannitol and sucrose) showed potential incompatibilities by DSC and LC analysis after accelerated stability testing. However, some incompatibilities were not detected by the DSC method and were observed only when LC analysis was performed. HSM was able to differentiate active pharmaceutical ingredient degradation from solubilisation, supporting the interpretation of DSC in excipients where thermal events either overlapped or disappeared. The combination of both the analytical techniques (DSC and LC) and use of a stability chamber is extremely helpful in detecting incompatibilities and providing more robust and accurate approaches for pre-formulation studies.

Characterization and compatibility study of desloratadine

Desloratadine (DL) is a selective antagonist of the histamine H1 receptor, which has been widely used to treat allergic symptoms, and stands out from other drugs in this therapeutic class because it does not cause sedative effects. In the present study, the physico-chemical properties of DL were fully characterized using six analytical techniques such as Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TG/DTG), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The DSC curve shows a sharp endothermic event at 158.4xa0°C, and the TG/DTG curve presents two decomposition events between 178.4 and 451.9xa0°C. A compatibility study involving DL and nine pharmaceutical excipients generally used in pharmaceutical formulations was performed. Physical binary mixtures of DL with each excipient were prepared in a 1:1 (w/w) ratio. After preparation, the samples were analyzed immediately and the results reveal solid-state interaction with anhydrous lactose, microcrystalline cellulose, magnesium stearate, and stearic acid.

Development, characterization, and stability studies of ethinyl estradiol solid dispersion

Innovative pharmaceutical development in an attempt to enhance the bioavailability of poorly water-soluble drugs is supporting the increase in solid dispersion (SD) technology by using different excipients and solvents. Ethinyl estradiol (EE) is an estrogen component that presents poor solubility and is commercialized at low concentrations (usually 30 or 35xa0μg). A full solid-state characterization of EE was conducted using differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy to examine its physicochemical properties and polymorphic state. The main aim of this work was to develop and characterize a stable SD containing EE and pharmaceutical excipients, to enhance the drug solubility. For this task, four excipients (starch, microcrystalline cellulose, lactose, and PVP) and four solvents (ethanol, acetone, dichloromethane, and chloroform) were tested. Each prepared sample was monitored by DSC and PXRD to evaluate the SD formation. Stability tests were performed with the successful SD that was stored under three different conditions [75xa0% relative humidity (RH)/40xa0°C; 90xa0% RH/25xa0°C; and 0xa0% RH/25xa0°C] and analyzed after 15 and 30xa0days by DSC and PXRD. The results showed that polyvinylpyrrolidone combined with any solvents was able to consistently produce a stable solid dispersion with EE.

Mapping the polymorphic forms of fexofenadine in pharmaceutical tablets using near infrared chemical imaging

This study presents a comparison of partial least squares (PLS) and multivariate curve resolution (MCR-ALS) in the quantification of polymorphic forms I and II of fexofenadine. HCl in pharmaceutical tablets using near infrared chemical imaging (NIR-CI). The PLS model built using a standard normal variate (SNV) pre-processing method resulted in satisfactory fits between the reference and predicted values, with a root mean square error of prediction (RMSEP) for both polymorphic forms below 1.5% (w/w). The MCR-ALS results were obtained using an augmented matrix and SNV pre-processing method. The lack of fit value for decomposition was 0.13%, the correlation coefficient between the pure spectra and the obtained spectral profiles was 99.94% and the RMSEP was below 6% (w/w). The MCR-ALS model efficiently quantified the polymorphic forms and generated distribution maps; however, the PLS model exhibited better recovery of the concentrations.

Electrochemical Oxidation, Adsorption and Quantification of 1,2-Benzopyrone Employing a Glassy Carbon Electrode

The electrooxidation of 1,2-benzopyrone (BP) was assessed via linear voltammetry and electrochemical impedance spectroscopy on a glassy carbon electrode in dibasic potassium phosphate buffer. The oxidation process for BP requires one electron and forms a ketone. This oxidation product was adsorbed by the electrode surface to form a film that blocks active sites and increases in thickness over consecutive measurements. The oxidation conditions were optimized using factorial design and Doehlert matrices. This electrochemical method was compared to high performance liquid chromatography (HPLC), which has a detection limit of 26.4 µmol L-1 for BP. The voltammetric results were statistically similar to those from HPLC; however, the method was faster, simpler, more easily acquired, more sensitive, and required less organic solvent.

Compatibility and stability of valsartan in a solid pharmaceutical formulation

Valsartan (VAL) is a highly selective blocker of the angiotensin II receptor that has been widely used in the treatment of hypertension. Active pharmaceutical ingredient compatibility with excipients (crospovidone, hypromellose, magnesium stearate, microcrystalline cellulose and titanium dioxide) is usually evaluated in solid pharmaceutical development. Compatibility and stability can be evaluated by liquid chromatography. Studies were performed using binary mixtures of 1:1 (w/w) VAL/excipient; samples were stored under accelerated stability test conditions (40 oC at 75% relative humidity). The results indicate that VAL is incompatible with crospovidone and hypromellose, which reduced the VAL content and gave rise to new peaks in the chromatogram due to degradation products.

Effects of Cadmium and Copper Biosorption on Chlorella vulgaris

AbstractnChanges in protein levels and lipid compositions in algal cells indicate the severity of stress related to toxic concentrations of heavy metals. In this study, the effects of exposure to cadmium and copper on Chlorella vulgaris and its capacity to remove metals were evaluated. The data revealed ion removal activity by microalgae under all treatments and different levels of protein expression after 48xa0h of exposure. Furthermore, we analyzed lipids contents to characterize them.

Differential Scanning Calorimetry and Infrared Spectroscopy Combined with Chemometric Analysis to the Determination of Coffee Adulteration by Corn

Roasted and ground coffee is targeted by fraudulent addiction of products. In this way the determination of contaminants in coffee has economic and nutritional importance. In this study, the coffee adulteration by corn were detected using DSC (differential scanning calorimetry) and FTIR (Fourier transform infrared spectroscopy) coupled to PCA (principal component analysis), and PLS (partial least squares) models. Three different levels of roasted and ground Coffea arabica L. were used to prepare mixtures with roasted and ground corn. The level of adulteration used was between 0.5 to 40% (m/m). It was observed that both DSC and FTIR coupled with PCA are able to discriminate adulterated from unadulterated samples of coffee by corn at levels below 1%. PLS models were built with DSC and FTIR data reaching good correlation between the values of estimated and reference concentrations, with RMSECV (root mean square error of cross-validation) lower than 3.5% for DSC data and 2.7% for FTIR data.

Interactions fulvate-metal (Zn²⁺, Cu²⁺ and Fe²⁺): theoretical investigation of thermodynamic, structural and spectroscopic properties.

The use of theoretical calculation to determine structural properties of fulvate-metal complex (zinc, copper and iron) is here related. The species were proposed in the ratio 1:1 and 2:1 for which the molecular structure was obtained through the semi-empirical method PM6. The calculation of thermodynamic stability (