Scielo RSS <![CDATA[Química Nova]]> vol. 40 num. 7 lang. es <![CDATA[SciELO Logo]]> <![CDATA[USE OF MIP OES AND F AAS/AES FOR DETERMINATION OF Ca, K, Na AND Mg IN BRAZILIAN CREAM CHEESE]]> In this work, two sample preparation procedures for subsequent determination of Na, K, Ca and Mg by techniques of atomic spectrometry in samples of Brazilian cream cheese were evaluated. The determinations were performed on two equipments, F AAS and MIP OES, which presented similar results, being evident the advantages of MIP OES since it is a multielementar technique with low operational cost and high efficiency. The first procedure was carried out by acidic decomposition (HNO3/H2SO4) in a reflux system, and the second used the alkaline solubilization with tetramethylammonium hydroxide. The accuracy was verified by recovery tests and the results were between 80 and 104% for both procedures. A comparison with a reference procedure was also performed and no significant differences have been observed at the 95% confidence level. The evaluated elements were not in accordance with the values indicated on the labels of all products, showing the importance for monitoring these products. The methods of sample preparation proposed showed to be simple, inexpensive, providing accurate and precise results, and are a promising alternative to be used for the quality control of these routine test samples. <![CDATA[FIXATION OF CO<sub>2</sub> IN BRINES OF PETROCHEMICAL INDUSTRY]]> In various industrial processes, such as the process of obtaining potassium by solution mining or in the oil industry, fuels are burnt concurrently to the formation of saline effluents. The opportunity to sequester carbon through capturing the CO2 from the flue gas by carbonation of these effluents and reducing the potential of scaling of the water is evident. The use of saline industrial effluent from electrodialysis for carbon sequestration by mineralization of carbon dioxide is the focus of this work. The carbonation reaction of saline effluent of reverse electrodialysis, of low ionic strength and higher CO2 solubility, was simulated through OLI®. Precipitation tests were performed by bubbling 10-20 NL h-1 CO2 in a glass reactor containing the brine and pH adjusted to 8.9. The solid was characterized and the results from the simulation and the experiments were compared. The removal of calcium and strontium in the form of carbonates reach out up to 98% and 75%. The simulation results were in line with the experimental results for the calcium behavior, but not for strontium. The OLI® simulation was powerful to represent the calcium carbonate formation, however, comparisons between predicted Sr removal and testwork results presented differences and must be investigated. <![CDATA[CHEMICAL EQUILIBRIUM AND ENZYMATIC KINETICS OF α-AMYLASE INTERACTION WITH PHENOLIC COMPOUNDS FOUND IN BEER]]> α-amylase is a key enzyme in the production of beer due to the breakdown of starch into fermentable sugars. During the preparation of the brewing mash, the enzyme can be affected by polyphenols present in the mixture. Our aim was to evaluate the kinetics and equilibrium of the interaction of α-amylase with some polyphenols (chlorogenic, caffeic, ferulic acids and quercetin) present in beer in the usual range of mashing temperatures (40 - 80 °C), and to treat the results with integrated Michaelis-Menten and Stern-Volmer equations. The results showed a competitive inhibition model for all compounds with Ki values around 30 umol.L-1. The binding constants (Kb) revealed increasing values with temperature up to 323 K, corroborating the enzymatic data. Values for ΔH and ΔS revealed an entropy-driven association mechanism. Structure-activity relationships demonstrated a positive correlation between the biological activity of α-amylase and the polar nature descriptors of the polyphenols. Binding assays of the enzyme with chlorogenic acid at different pH and ionic strength support the structure-activity and thermodynamic data and suggest a plausible interaction of the carboxylate ion of the ligand with basic groups in the vicinity of the catalytic site of the enzyme. <![CDATA[A NOVEL RHODAMINE-BASED FLUORESCENCE CHEMOSENSOR CONTAINING POLYETHER FOR MERCURY (II) IONS IN AQUEOUS SOLUTION]]> A novel rhodamine-based Hg2+ chemosensor P2 containing polyether was readily synthesized and investigated, which displayed high selectivity and sensitivity for Hg2+. Because of good water-solubility of polyther, the rhodamine-based chemosensor containing polyether can be used in aqueous solution. The sensor responded rapidly to Hg2+ in pure water solutions with a 1:1 stoichiometry. Meanwhile, it indicated excellent adaptability and also the responsiveness. <![CDATA[AMPEROMETRIC DETERMINATION OF 8-CHLOROTHEOPHYLLINE, CAFFEINE, AND DIPHENHYDRAMINE IN A SINGLE RUN]]> A simple method for simultaneous determination of 8-chlorotheophylline (CTP), caffeine (CAF), and diphenhydramine (DIP) using batch-injection analysis with multiple pulse amperometric detection (BIA-MPA) is reported. A sequence of three potential pulses (+1.10 V, +1.40 V, and +1.70 V) was applied to the boron-doped diamond working electrode with the acquisition of three distinct amperograms. CTP was detected selectively at +1.10 V, both CTP + CAF at +1.40 V and CTP + CAF + DIP at +1.70 V. The subtraction between the currents detected at the three potential pulses (with the use of correction factors) was the strategy used to achieve selectivity for the determination of CAF and DIP. The proposed method is simple, inexpensive, fast (120 injections h-1), presents good precision (RSD &lt; 0.9%; n = 20), and adequate limits of detection (0.31, 0.49, and 0.76 µmol L-1 for CTP, CAF and DIP, respectively). The results obtained by BIA-MPA were similar to those found by high-performance liquid chromatography (95% confidence level). <![CDATA[CHARACTERIZATION OF ENALAPRIL AND RANITIDINE CHLORINATION BY-PRODUCTS BY LIQUID CHROMATOGRAPHY/HIGH-RESOLUTION MASS SPECTROMETRY AND THEIR TOXICITY EVALUATION]]> Due to its low cost, its capability for disinfection and oxidation, chlorination using gaseous chlorine or hypochlorite salts, has also been commonly applied in water treatment plants for oxidation and disinfection purposes. Little is known about the identity and toxicity of by-products resulting from the chlorination of pharmaceutical micropollutants, such as enalapril (ENA) and ranitidine (RAN). ENA and RAN chlorination by-products were characterized in this study by high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC/HRMS) and their toxicity were assessed by MTT assay. Chlorination experiments with ENA and RAN solutions (10 mg L-1) indicate degradation efficiencies of 100% for both compounds after only 5 min of exposure to chlorine at concentration of 9.53 mg Cl2 L-1. On the other hand mineralization rates were lower than 3%, thereby indicating there was accumulation of degradation by-products in all experiments. Mass spectrometric analysis revealed, at all times of reaction after the addition of hypochlorite, the presence of 1-(2-((4-(chlorophenyl)-1-ethoxy-1-oxobutan-2-yl)amino)propanoyl)pyrrolidine-2-carboxylic acid (enalapril by-product) and N-chloro-N-(2-(((chloro-5-((dimethylamino)methyl)furan-2-yl)methyl)sulfinyl)ethyl)-N-methyl-2-nitroethene 1,1-diamine (ranitidine by-product). Despite the formation of oxidized chlorinated by-products in all chlorination assays, the treated solutions were nontoxic to HepG2 cells by the MTT assay. It has been observed that chlorination (10 mg L-1, 5 min) of ENA and RAN solutions exhibited high degradation efficiencies of the target compounds and low mineralization rates. Based on the mass spectrometry data, the routes for ENA and RAN successive oxidation by chlorine has been proposed. <![CDATA[FAST AND SIMPLE DETERMINATION OF SILDENAFIL CITRATE (VIAGRA<sup>®</sup> AND GENERICS) USING CARBON SCREEN-PRINTED ELECTRODE IN FIA AND BIA SYSTEMS WITH AMPEROMETRIC DETECTION]]> This work presents two amperometric methods for Sildenafil Citrate (SC) determination in erectile dysfunction drugs (Viagra® and Generics), using Batch Injection Analysis (BIA) and Flow Injection Analysis (FIA) systems with a cell for Screen Printed Electrodes (SPE). In Britton- Robinson buffer solution (pH 2), the SC presented an irreversible anodic peak at around +1.0 V vs. Ag pseudo-reference electrode, using five different working electrodes of commercial SPE. The carbon SPE (unmodified) was selected as the best working electrode, providing good sensitivity, precision and low-cost. The SC amperometric detection for two proposed methods was performed at +1.1 V. The best conditions for SC determination by hydrodynamic systems were obtained through injection volumes of 50 and 150 µL at flow rates of 100 and 75 µL s-1, for BIA and FIA respectively. In these conditions, BIA system showed the best sensitivity (0.188 µA mol-1 L) and theoretical analytical frequency (360 h-1) for SC determination. The repeatability studies were similar for both systems with relative standard deviation of approximately 3.0%. The SC analyses in pharmaceutical samples obtained by two proposed methods were compared to HPLC-UV method. <![CDATA[EFFICIENCY OF THE HETEROCYCLE ISATIN LOADED IN MICROEMULSIONS AS CORROSION INHIBITOR FOR MILD STEEL IN SALINE MEDIUM]]> Polar microemulsion systems (SME) based on saponified coconut oil (OCS) as surfactant were prepared in order to increase the solubility of the heterocycle isatin (IST) aiming at its application as corrosion inhibitor against AISI 1020 mild steel, in saline medium. The adsorptions phenomena of the tested SME systems (SME-OCS1-IST and SME-OCS2-IST) in the liquid/gas interface were evaluated by surface tension measurements which do not show significant differences in the presence of ion Cl-. The free energy values of the micellization proved the occurrence of spontaneous process. The corrosion inhibition effectiveness of SME-OCS2, SME-OCS1-IST and SME-OCS2-IST samples was evaluated in 0.5% aqueous NaCl using voltammetry linear scan method (LPR). The maximum efficiency findings were 73.2% for SME-OCS2, 88.2% for SME-OCS2-IST and 97.6% for SME-OCS1-IST. The spontaneity of the adsorption phenomena was also observed in the liquid/metal interface by analyzes of the adsorption free energy. In addition, since computational calculations have been found as a very relevant tool in the corrosion field, a theoretical study was performed in attempt to give support to the observed experimental results, in which B3LYP and 6-311++G(d,p) were applied aiming at investigation of geometry, electronic density aspects, HOMO-LUMO energy gap, as well as the binding between isatin and metal surface. <![CDATA[MECHANISTIC STUDY OF THE FENTON AND CUPRO-FENTON REACTIONS BY VOLTAMMETRIC ANALYSIS <em>IN SITU</em>]]> Although the classical Fenton process exhibits a high initial rate of the organic compounds degradation, this process is not complete due to the formation of refractory compounds which resist the attack of the hydroxyl radicals. In the presence of Cu(II), the degradation is slower, but results in a greater reduction of TOC (total organic carbon) measurements of net mineralization at the end of the reaction (t=120min). The addition of Cu(II) ions to classical Fenton reaction conditions (Fe(II) plus H2O2 at pH 3) is shown to accelerate the degradation of organic compounds. This synergic effect causes an approximately 15% additional reduction of the TOC. Voltammetric studies confirm the catalytic role of catechol in the presence of Fe(III)/Fe(II) and Cu(II)/Cu(I). Addition of aliphatic acids to the reaction medium, did not interfere with the cupro-Fenton reaction, but had an inhibitory effect on the classical Fenton reaction, consistent with the following order of interaction with the ion Fe(III): Oxalic Acid (OA) &gt;&gt; Formic Acid (FA) ~ Acetic acid (AA). <![CDATA[ELUCIDATION OF THE ELECTRONIC SPECTRUM CHANGES OF KA-Al<sup>3+</sup> COMPLEX BY POTENTIOMETRIC TITRATION, FTIR, <sup>13</sup>C RMN AND QUANTUM MECHANICS]]> Kojic acid (KA) is an organic acid widely used in pharmaceutical industry, mainly as a skin lightening agent. Based on the ability of KA to form complexes with ions, we found the most possible kind of complex formed with cation aluminum. KA-Al3+ complex structures were studied using potentiometric and spectrophotometric (UV) titrations, FTIR and 13C NMR. The electronic spectroscopy showed that the KA-Al3+ complexes absorb at higher wavelengths (λmax= 305 nm) than do the non-complexed KA (λmax= 269 nm), confirming complexation. The IR spectra of KA complexed and not complexed allowed us to correlate the changes in the absorption of enol and carbonyl groups in absence and presence of Al3+ in aqueous solutions. The complexation suggested by the potentiometric titration and FTIR spectroscopy are in accordance with the data obtained from NMR results. Calculations based on quantum mechanics were utilized to understand the differences found in the noncomplexed and complexed KAH electronic spectra <![CDATA[ASSESSMENT OF PARALOID<sup>®</sup> B-72 PENETRATION IN WHITE CERAMIC STUDIED BY NEUTRON TOMOGRAPHY]]> The neutron tomography technique was employed to study the penetration and distribution of the consolidant Paraloid® B-72 in ceramic. This study was carried out in white contemporary ceramic vessels which were maintained in two distinct and controlled air humidity conditions, 35% and 90%, before the consolidant application (brushing technique). The results showed that the treatment with Paraloid® B-72 is more effective when applied in the drier vessel. The depth of penetration for the vessel at 35%, reaches (3.3 ± 0.1) mm in the wall, while for the one at 90%, (1.9 ± 0.1) mm, and the maximal concentration impregnation was 26% higher. The 3D images allowed a visualization of the impregnation process, that is, its distribution, failures, homogeneity, boundary between materials. These results demonstrated the feasibility of the neutron tomography technique and of the equipment of IPEN-CNEN/SP, in support the expert work in the field of preservation and restoration of ceramic objects. <![CDATA[DETERMINATION OF SULFUR IN SHAMPOO BY UV-VIS SPECTROPHOTOMETRY: EVALUATION OF SAMPLE PREPARATION METHODS]]> Dry ashing, dissolution in aqueous medium or wet digestion methods were evaluated for sample preparation of shampoo for the subsequent indirect determination of sulfur by UV-Vis spectrophotometry. Among the sample preparation methods evaluated, microwave-assisted wet digestion using 7 mol L-1 HNO3 was the most suitable method for this purpose. Accuracy of the proposed method was evaluated by recovery test using standard solution, and the recovery was about 96%. Moreover, for comparison of results, S (as SO42-) was also determined by ion chromatography, after microwave-assisted wet digestion using concentrated HNO3, and no significant difference was observed between the obtained results (according to the t-test for a 95% confidence level, p = 0.288). Relative standard deviations were always lower than 10% and the limit of detection was 0.007% w/v. Finally, the proposed method was applied for analysis of sixteen shampoos used to many types of hair, from different brands produced in Brazil, and the concentration of S ranged from 0.78 to 2.82% w/v. <![CDATA[SYNTHESES AND PROPERTIES OF DRUGS INHIBITORS OF BCR-ABL TYROSINE KINASE, USED IN THE TREATMENT OF CHRONIC MYELOID LEUKEMIA]]> The chronic myeloid leukemia (CML) is characterized by presence of the Philadelphia chromosome (Ph), originated from the translocation between chromosomes 9 and 22. This chromosome generates an abnormal protein tyrosine kinase which is responsible for tumor cell proliferation. The emergence of tyrosine kinase inhibitors (TKIs) has transformed the treatment of CML and imatinib being the first representative of this class. Although treatment with imatinib has reached surprising results, approximately 30% of patients exhibited resistance, especially in later stages of the disease. This fact stimulated the development of novel BCR-ABL enzyme inhibitors drugs classified as tyrosine kinase inhibitors (TKIs) of second and third generations. The TKIs have different chemical functions in their structure, and the knowledge of synthetic methods for preparation of these compounds can be a powerful tool for the development of new derivatives. The five approved BCR-ABL Tyrosine Kinase inhibitors (TKI) used in Chronic Myeloid Leukemia (CML) are reviewed aiming the main synthetic routes, highlighting the advantages and disadvantages associated with them. <![CDATA[POLYMERSOMES <em>VERSUS</em> LIPOSOMES: THE "MAGIC BULLET" EVOLUTION]]> Polymeric vesicles known as polymersomes are formed by the self-assemble of amphiphilic block copolymers and have structural organization similar to liposomes. However, polymersomes present higher physicochemical stability and structure versatility due to their polymeric nature. In this review we describe the main aspects related to the structure and applications of these systems for drug delivery. <![CDATA[RAPID SPECTROPHOTOMETRIC DIFFERENTIATION BETWEEN PALM OIL BIODIESEL AND RED DYE ADDED TO DIESEL FUEL]]> Currently, there are two mixtures of biodiesel/diesel fuel sold in Brazil: BX/S500 and BX /S10 (X = volume/volume biodiesel percentage; S500 and S10 = sulfur content in diesel fuels - 500 ppm and 10 ppm, respectively). In order to differentiate these mixtures, red dye is added to diesel oil as required by the National Agency for Petroleum, Natural Gas and Biofuels (ANP), regulatory agency in Brazil. Since the palm oil biodiesel has also a reddish color, mixing this product with diesel fuel leads to difficulty in visual differentiation of the mixtures BX/S500 and BX/S10. We propose the use of UV-Vis spectrophotometry, which is a low cost, simple and rapid technique. Spectra obtained for different mixtures show that qualitative distinction is possible. For quantification of red dye in the presence of palm oil biodiesel, the method is limited when dye is present in low concentrations (&lt; 0.1 mg L-1) due to matrix effects. The method showed good repeatability of the absorbance responses, wide linear dynamic range (0.02 mg L-1 to 40.00 mg L-1) and low limits of detection and quantification (0.006 mg L-1 and 0.019 mg L-1, respectively). <![CDATA[REACTIVITY AND SOLUBILITY OF GASES]]> This paper deals with the solubility and reactivity of gases, especially in water, covering the main aspects that influence the dissolution process, namely polarizability of atoms or molecules in gas phase and their ability to react with the solvent. The discussion highlights the importance of solubility of gases in several biological processes, such as respiration and photosynthesis, hydrogen storage and industrial processes, as the production of carbonated beverages. The discussion also addresses the importance of gas solubility in atmospheric chemistry and aquatic environments. <![CDATA[PHOSPHATE COLORIMETRIC ANALYSIS USING A DESKTOP SCANNER AND AUTOMATED DIGITAL IMAGE ANALYSIS: A DIDATICAL EXAMPLE TO TEACH COLORIMETRIC ANALYSES]]> We propose here the quantification of the phosphorus content in cola drinks by molybdenum blue method. Molybdenum blue method was carried out in the wells of a microplate, where method miniaturization represents reduction in reagents required, improved safety, reduced waste stream, and increased sample throughput. The phosphate concentration was determinate using scanned images of the microplate. Extraction of RGB values was carried out using ImageJ, the pugling Readplate was used allowing extraction of RGB values of all wells simultaneously. A Microsoft Excel spreadsheet is afforded in Google Drive, it organize data taken from ImageJ to afford calibrations curves and phosphate concentration in cola drinks. Calibration curves were prepared at 500-2500 µg L-1 of P with good linearity (R &gt; 0.95). Phosphate concentrations in cola drinks determinate using digital images method are statistically equivalent to concentrations determined using a spectroscopic method at a 95% confidence interval. <![CDATA[PATENT ANALYSIS: A LOOK AT THE INNOVATIVE NATURE OF PLANT-BASED COSMETICS]]> The use of plants have become a important trend in cosmetic market, with a crescent number of patent applications. Despite various herbal-based ingredients have been described in scientific literature, most of them are restricted to patent databases. In this work we analyze the innovative use of plants and its derivatives in cosmetic technologies, based on patent analysis. The investigation was conducted using Derwent World Patents Index (Thomson Reuters Scientific, USA) from 1995 to 2015. The search was carried out to evaluate the number of patent deposits, the patent depositors profiles, the countries with most patent applications, the International Patent Classification (IPC) and the main plant families using in cosmetics. Patent analysis revealed an increase number of applications involving cosmetic containing plants components, with a higher number of deposits related to anti-ageing and whitening skin treatment. Fabaceae, Asteraceae, Rosaceae, Lamiaceae, Poaceae, Rutaceae, Lilliacae and Apiaceae were the key plant families used in cosmetic formulations for skin care treatment. Comparison between scientific and technological data pointed out divergences between patents deposits and aid-based scientific reports. The use of patent analysis in combination with scientific data opens up wider aspects of knowledge and enables a better rationalization of innovative works.