Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> http://www.scielo.br/rss.php?pid=0103-505320160001&lang=pt vol. 27 num. 1 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[2016, What Lies Ahead?]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100001&lng=pt&nrm=iso&tlng=pt <![CDATA[<em>In vitro</em> Anti-HMPV Activity of New Synthetic Phenytoin Derivatives]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100002&lng=pt&nrm=iso&tlng=pt New derivatives of synthetic 5,5-diphenylhydantoin (phenytoin) were prepared by N-alkylation with 1,3-dibromopropane. Subsequent treatment with sodium azide led to the respective azide. Reaction of the azide with phenylacetylene and 2-hydroxy-3-butyne and oxidation of the resulting alcohol with MnO2 resulted in three triazolic compounds that were evaluated in vitro for their antiviral activity against human metapneumovirus (HMPV). 5,5-Diphenyl-3-[3-(4-phenyl-1H-1,2,3-triazol-1-yl)propyl]imidazolidine-2,4-dione was the most active of the three compounds tested, with selectivity index of 129.87, even higher than ribavirin, the control substance. The three compounds showed activity in the early stages of viral replication presenting virucidal activity and binding to cellular receptors, preventing the adsorption of viral particles. These compounds showed higher activity in both experiments, inhibiting 98.3% of infection as virucidal and 98.9% when interacting with cellular receptors. Furthermore, they showed 73.8% of activity during the penetration of HMPV particles into cells. The derivative 3-{3-[4-(1-hydroxyethyl)-1H-1,2,3-triazol-1-yl]propyl}-5,5-diphenylimidazolidine-2,4-dione presented a mild anti-HMPV activity, with selectivity index of 2.74. 3-[3-(4-acetyl-1H-1,2,3-triazol-1-yl)propyl]-5,5-diphenylimidazolidine-2,4-dione inhibited less than 50% of HMPV replication. <![CDATA[New Biphenyls from <em>Garcinia multiflora</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100010&lng=pt&nrm=iso&tlng=pt Three new biphenyls were isolated from Garcinia multiflora. The structures of these biphenyls were elucidated by spectroscopic methods, and their rotavirus activity was evaluated. <![CDATA[Equilibrium and Out-Of-Equilibrium Investigation of Proton Exchange and Cu<sup>II</sup> and Zn<sup>II</sup> Complexation on Fungal Mycelium (<em>Trametes hirsuta</em>)]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100015&lng=pt&nrm=iso&tlng=pt This work presents potentiometric investigations of [mycelium/metal ion/water] complex systems and the development of a new model investigating the ion-mycelium-fluid interactions. Since pH is a major parameter in soil ecology exhibiting large fluctuations, we proposed an improved equilibrium and also out-of-equilibrium potentiometric titration method in order to characterize the proton exchange behavior of the [mycelium/metal ion/water] system. Our model describes the dynamic relations and interactions within the soil complex subsystems consisting of fungal mycelium of Trametes hirsuta, water with or without metal ions (CuII and ZnII). Equilibrium modeling based on potentiometric titrations can be well described using four mycelium related components which are active in the pH range studied. In addition, our equilibrium calculations show clear differences with respect to metal-mycelium interactions: CuII interacts with acidic and basic deprotonable sites, while ZnII binds with neutral and basic deprotonable sites. Potentiometric out-of-equilibrium (i.e., perturbed pH) characterization suggests that important fungal heterogeneous complexity may act as definite proton pressure entities under continuously perturbed soil conditions. Raman micro-spectroscopy was also used to characterize the [mycelium/metal ion/water] complex systems. Our results demonstrate that potentiometry is a useful tool (intermediate technology) in studying biological complex matrices, facing pH perturbations, as well as their interactions with metal ions. <![CDATA[Anti-<em>Mycobacterium tuberculosis</em> and Cytotoxicity Activities of Ruthenium(II)/ Bipyridine/Diphosphine/Pyrimidine-2-thiolate Complexes: The Role of the Non- Coordinated N-Atom]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100030&lng=pt&nrm=iso&tlng=pt The [Ru(Spym)(bipy)(P–P)]PF6, [Spym = pyrimidine-2-thiolate anion; P–P = 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane and 1,1'-bis(diphenylphosphino)ferrocene] complexes were synthesized and characterized by spectroscopic, electrochemical and elemental analysis, and by X-ray crystallography. The minimal inhibitory concentration (MIC) of the compounds against Mycobacterium tuberculosis and the complex concentration causing 50% tumor cell growth inhibition (IC50) against breast cancer cells, MDA-MB-231, were determined. All three compounds gave promising values in both tests. It is interesting to mention that all three complexes display MICs against Mycobacteriumtuberculosis showing higher activity than cycloserine, a second line drug used in the treatment of the illness. The complexes interact weakly with the DNA. <![CDATA[7-Chloroquinoline-1,2,3-triazoyl Carboxylates: Organocatalytic Synthesis and Antioxidant Properties]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100041&lng=pt&nrm=iso&tlng=pt We describe herein our results on the synthesis and antioxidant properties of 7-chloroquinoline-1,2,3-triazoyl-4-carboxylates. This class of compounds have been synthesized in moderated to excellent yields by the reaction of 4-azido-7-chloroquinoline with a range of β-ketoesters in the presence of a catalytic amount of pyrrolidine (10 mol%). The synthesized compounds ethyl 1-(7-chloroquinolin-4-yl)-5-methyl-1H-1,2,3-triazole-4-carboxylate and ethyl 1-(7-chloroquinolin-4-yl)-5-phenyl-1H-1,2,3-triazole-4-carboxylate were screened for their in vitro antioxidant activity and the results demonstrated that the first compound reduces the lipid peroxidation levels induced by sodium nitroprusside in liver of mice, while the second compound shown nitric oxide scavenging activity. This is an efficient method to produce new heterocyclic compounds with potential antioxidant activities. <![CDATA[Development of a Molecularly Imprinted Modified Electrode to Evaluate Phenacetin Based on the Preconcentration of Acetaminophen]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100054&lng=pt&nrm=iso&tlng=pt A glassy carbon electrode modified with a molecularly imprinted polymer (MIP) containing phenacetin recognition sites is introduced. The phenacetin-selective MIP was synthesised based on the electropolymerisation of pyrrole in a 1:1 (v/v) water/ethanol with HClO4 solution. The MIP-modified electrode showed higher recognition ability in comparison with a bare electrode for procaine and aminopyrine, reported to electrochemically interfere in the quantification of phenacetin in cocaine samples. In addition, the MIP was able to preconcentrate one of the intermediates of the phenacetin electrochemical oxidation, acetaminophen, indicating the possibility of monitoring phenacetin based on the acetaminophen oxidation. The acetaminophen oxidation peak is 15 times more detectable compared to the signal obtained by the non-molecularly imprinted polymer (NIP), and it occurs 450 mV below the phenacetin electrochemical oxidation signal. These achieved characteristics decrease the possibility of interference from other electrochemical reactions that may occur in the same potential range as phenacetin electrochemical process. <![CDATA[Application of Multivariate Analysis to Assess the Incorporation of Omega-3 Fatty Acid in Gluten-Free Cakes]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100062&lng=pt&nrm=iso&tlng=pt A complete 22 experimental planning (two factors at two levels) with central point in quintuplicate was used to investigate the influence of the factors: chia and azuki flours on fatty acids composition of gluten-free chocolate cake. Both factors were significant, but chia flour presented greater influence on the results. Increased values of both factors contributed to improve contents of polyunsaturated fatty acids (380.96 g kg-1 of product), mainly n-3 series (70.25 g kg-1 of product), and provided more adequate nutritional indices. The principal component analysis and desirability function indicated the sample with higher level of both factors as the optimal region. This sample showed an increase in contents of alpha-linolenic acid (188.03%) and polyunsaturated fatty acids (18.16%) when compared to control formulation. The addition of chia flour can improve nutritional characteristics of food stuffs such as bakery products, especially their lipid composition. <![CDATA[Use of a Digital Image in Flow Analysis: Determination of Nitrite and Nitrate in Natural Waters]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100070&lng=pt&nrm=iso&tlng=pt A webcam is proposed as the detector in a flow system with multicommutation, and the feasibility of the approach is demonstrated in the determination of nitrate and nitrite in natural waters. The typical transient signal inherent to the flow system was obtained using a digital video and quantified by ImageJ software. The linear dynamics range for nitrite and nitrate determinations were 0.2 to 2.0 mg L-1 NO2− and 1.0 to 10.0 mg L-1 NO3−, with relative standard deviation &lt; 2% for both analytes. The limits of detection were 0.01 and 0.04 mg L-1 for nitrite for nitrate, respectively, and the sampling rate were 80 and 103 h-1 for nitrite and nitrate, respectively. The use of webcams has a high potential for analysis in the visible region of the electromagnetic spectrum, and the proposed strategy constitutes a promising alternative to traditional absorbance measurements that depend on conventional equipment. The webcam detection system is attractive, especially in relation to field analysis. <![CDATA[Dielectric Behavior of Alginate-Based Hydrogel Containing Neomycin-Loaded Lipid Nanovesicles under Influence of Electrical Potentials]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100077&lng=pt&nrm=iso&tlng=pt Dielectric characterization has been applied as a convenient tool for evaluation of transport and polarization mechanisms in soft materials. In this work, we have explored the study of charge transport mechanisms in alginate hydrogel containing neomycin-loaded liposomes. For comparison, drug release kinetic was evaluated by using UV-Vis spectrophotometry and electrical impedance spectroscopy (EIS) at different external direct current (DC) polarization (100 mV and 1 V). The charge transfer resistance (Rct) was proportional to DC electrical stimulation and inversely to the amount of released neomycin. Optical and electrical measurements confirmed the dependence of neomycin release under influence of electrical potentials. The kinetic profile of these systems was described by zero-order model. In addition, the Korsmeyer-Peppas model also suggested a diffusion mechanism based on super case II transport (non-Fickian). These results encouraged the use of EIS as a “dark" spectroscopy technique, since EIS is effective for studies of release kinetics controlled by DC external electrical excitation. <![CDATA[Qualitative and Quantitative Monitoring of Methyl Cotton Biodiesel Content in Biodiesel/Diesel Blends Using MIR Spectroscopy and Chemometrics Tools]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100084&lng=pt&nrm=iso&tlng=pt This paper presents methodologies for monitoring the quality of methyl cotton biodiesel in biodiesel/diesel blends using mid-infrared spectroscopy (MIR) and chemometrics tools. The first method relates to the construction of multivariate control charts with the aim of qualitatively monitoring the samples according to the Brazilian specification for biodiesel in the biodiesel/diesel blends (7.00 ± 0.5% v/v of biodiesel). The second concerns the construction of partial least squares (PLS) to determine the content of the biodiesel in the biodiesel/diesel blend. The PLS model was validated from multivariate figures of merit according to the guidelines of ASTM E1655-05 and IUPAC. The results from both methods were satisfactory for both qualitative and quantitative monitoring. Therefore, the proposed methodologies for monitoring the quality of biodiesel in biodiesel/diesel blends are fast, practical, economical and efficient and can be used by industries and service stations. <![CDATA[Antimicrobial Potential of Bio-Oil for Use in Diesel Oil B10]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100091&lng=pt&nrm=iso&tlng=pt The aim of this study was to evaluate the antimicrobial activity of bio-oil (obtained by pyrolysis of biomass: soybean oil, eucalyptus sawdust and coffee grounds) added to the blend B10 (diesel and biodiesel). The bio-oil is compatible to diesel oil and it contains promising compounds that can exhibit antimicrobial activity during fuel storage. We evaluated the antimicrobial activity of bio-oil added to diesel oil B10 by determining the minimum inhibitory concentration at different concentrations (0-10%) using oil-deteriorating microorganisms for 10 days at 30 °C. Bio-oil was separated from the aqueous phase by solid phase extraction using ultrapure water and sodium hydroxide. The aqueous phase containing the solubilized compounds of bio-oil was characterized by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection. Minimum inhibitory concentration in the range of 0.25% to 4% was observed for the tested inocula. The chromatographic analysis of both extracts allowed the identification of several oxygenated compounds, which the majority of the analytes consisted of phenolic compounds, followed by ketones. <![CDATA[Selective Separation of Silver(I) Ion Through a Bulk Liquid Membrane Containing 1,1'-(1,3-Phenylene)bis(3-allylthiourea) as Carrier]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100099&lng=pt&nrm=iso&tlng=pt The competitive bulk liquid membrane transport of six metal cations from an aqueous source phase (SP) containing Ag+, Pb2+, Cu2+, Zn2+, Co2+ and Ni2+ through an organic membrane phase (MP) facilitated by 1,1'-(1,3-phenylene)bis(3-allylthiourea) as a carrier into an aqueous receiving phase (RP) was studied and compared. Fluxes and selectivities for competitive metal cation transport have been determined in a variety of source solution pH and membrane solvent types. The obtained results showed that the carrier is selective for Ag+ cation. The effect of different experimental conditions that affect the transport efficiency were studied and optimized. In the optimum condition, the transport of a 5 × 10-4 mol L−1 solution of Ag+ cations was observed 92.3 ± 5.3% after 4 h in the presence of equimolar concentrations of other metal cations. A possible application of this carrier system and transport process for separation and recovery of Ag+ cation from real samples has also been examined. <![CDATA[Semi-Empirical Quantum Chemistry Method for Pre-Polymerization Rational Design of Ciprofloxacin Imprinted Polymer and Adsorption Studies]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100109&lng=pt&nrm=iso&tlng=pt It is well known that selectivity of molecularly imprinted polymers (MIPs) depends on adequate choice of functional monomer before the experimental synthesis. Computational simulation seems to be an ideal way to produce selective MIPs. In this work, we have proposed the use of semi-empirical simulation to obtain the best monomer able to strongly interact with ciprofloxacin. Twenty functional monomers were evaluated through semi-empirical quantum chemistry method and three MIPs were synthesized using the monomers acrylamide (M5), acrylic acid (M4) and 1-vinylimidazole (M16), yielding the maximum adsorption capacities of 282.0, 223.8 and 202.5 μmol g−1, respectively, as predicted by the computational simulation. From competitive adsorption studies in the presence of structurally similar compounds, the MIP synthesized with acrylamide was found to possess higher specific selectivity factors (S) if compared to non-imprinted polymer (NIP), thus indicating good recognition selectivity for the ciprofloxacin. <![CDATA[Fast Determination of Iron and Zinc in Hair and Human Serum Samples After Alkaline Solubilization by GF AAS]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100119&lng=pt&nrm=iso&tlng=pt Methods for the development and validation for determination of iron and zinc in human serum and hair samples by graphite furnace atomic absorption spectrometry (GF AAS) were performed. Solubilization was immediate by manual agitation in both samples with a 10 mL volume sample plus deionized water. Optimum pyrolysis and atomization temperatures were obtained by pyrolysis and atomization temperature curves in both matrices. For serum samples, the best temperatures were 1400 and 2500 °C (Fe) and 700 and 1600 °C (Zn), respectively. For hair samples, the best temperatures were 1000 and 2400 °C (Fe) and 800 and 1600 °C (Zn), respectively. Permanent modifiers and zirconium presented best the results for Zn in both matrices and for Fe in serum. Permanent modifier Nb was best for hair Zn. Serum and hair values were in agreement with the certified values for analytes and certified samples. The determined values for serum Fe and hair certified samples were 1.40 ± 0.2 and 114 ± 18 mg L-1, respectively. For Zn certified reference materials (CRMs), the certified samples values were 1720 ± 32 µg L-1 and 172 ± 5 mg kg-1. Simple, accurate and precise, this method represents a cost-effective detection protocol suitable for sample analysis for diagnosis of micronutrient malnutrition. <![CDATA[Estimating the Impact of an All-Electron Basis Set and Scalar Relativistic Effects on the Structure, Stability, and Reactivity of Small Copper Clusters]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100127&lng=pt&nrm=iso&tlng=pt Basis sets of valence double and quadruple zeta qualities and the Douglas-Kroll-Hess (DKH) approximation are used to estimate the impact of an all-electron basis set and scalar relativistic effects on the structure, stability, and electronic properties of small neutral copper clusters (Cun, n ≤ 8). At the Becke three-parameter for exchange and Perdew-Wang 91 for correlation (B3PW91) non-relativistic and relativistic levels of theory, the bond length, binding energy, ionization potential, electron affinity, chemical potential, chemical hardness, and electrophilicity index are calculated. The results show that the agreement with experiment improves significantly when the DKH Hamiltonian combined with an all-electron relativistic basis set is used. Polarizabilities and hyperpolarizability are also reported. At the B3PW91 level, all-electron basis sets are shown to be more reliable than effective core potential valence basis sets in the determination of the second hyperpolarizability of copper clusters. <![CDATA[Detailed <sup>1</sup>H and <sup>13</sup>C NMR Spectral Data Assignment for Two Dihydrobenzofuran Neolignans]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100136&lng=pt&nrm=iso&tlng=pt In this work we present a complete proton (1H) and carbon 13 (13C) nuclear magnetic resonance (NMR) spectral analysis of two synthetic dihydrofuran neolignans (±)-trans-dehydrodicoumarate dimethyl ester and (±)-trans-dehydrodiferulate dimethyl ester. Unequivocal assignments were achieved by 1H NMR, proton decoupled 13C (13C{1H}) NMR spectra, gradient-selected correlation spectroscopy (gCOSY), J-resolved, gradient-selected heteronuclear multiple quantum coherence (gHMQC), gradient-selected heteronuclear multiple bond coherence (gHMBC) and nuclear Overhauser effect spectroscopy (NOESY) experiments. All hydrogen coupling constants were measured, clarifying all the hydrogen signals multiplicities. Computational methods were also used to simulate the 1H and 13C chemical shifts and showed good agreement with the trans configuration of the substituents at C7 and C8. <![CDATA[Magnetic Nanoparticles Coated with Ionic Liquid as a Sorbent for Solid Phase Extraction of Chromium(VI) Prior to Its Determination by Electrothermal Atomic Absorption Spectrometry]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100144&lng=pt&nrm=iso&tlng=pt A simple, sensitive and reliable method for the separation, preconcentration and determination of ultra trace amounts of chromium species has been developed. Chromium(VI) in aqueous sample was reacted with 9-phenyl-2,3,7-trihydroxy-6-fluorone to produce a chelate at pH of 5.0 and extracted onto the magnetic nanoparticles coated with the ionic liquid 1-hexadecyl-3- methylimidazolium bromide. The trapped analyte was back extracted using 350 µL of nitric acid solution (2 mol L-1) and was determined by electrothermal atomic absorption spectrometry. Total chromium was determined by oxidizing CrIII to CrVI using KMnO4 in acidic media. Under the optimum conditions, the method exhibited a linear dynamic range of 0.01-0.50 µg L-1 with an enhancement factor of 112 and a detection limit of 0.003 µg L-1 for CrVI. The coefficient of variation (n = 6) at 0.3 µg L-1 concentration level of CrVI was 3.2%. <![CDATA[Development of a Procedure Based on Chemiluminescence and Multicommutation Approach for the Determination of Folic Acid in Pharmaceuticals]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100153&lng=pt&nrm=iso&tlng=pt This paper presents an analytical procedure for the determination of folic acid employing commutation flow analysis process and detection by chemiluminescence. The procedure is based on the reaction of hexacyanoferrate(III) with folic acid, followed of luminol oxidizing reaction in alkaline medium, resulting in emission of radiation at 425 nm. After optimization the experimental variables, the proposed procedure afforded the following useful features. A linear response ranging from 0.1 to 1.00 mg mL-1 folic acid (R2= 0.993), a detection limit (3σ criterion) 0.046 mg mL-1, a sampling rate of 156 determination per hour, a relative standard deviation less than 0.5% (n = 6) for a 0.6 mg mL-&gt;1 folic acid standard solution and a waste generation of 0.86 mL per determination. <![CDATA[Limonin Derivatives: Synthesis Using Methodology in Solution and Heterogeneous Medium and Evaluation of the Antimicrobial Activity]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100161&lng=pt&nrm=iso&tlng=pt We herein described the preparation of a novel series of limonin derivatives (modification in A-ring), which was synthesized efficiently using methodology in solution as well as in heterogeneous medium (K-10). In addition, we obtained derivatives by inserting the 1,2,3-triazole nucleus via click reaction and also prepared derivatives from reactions with limonin-7-oxime. All compounds were submitted to investigation of the antimicrobial activity against a collection of microorganisms. The results of the antimicrobial activity, in general, demonstrated that a relevant number of synthetic derivatives presented higher activity than the natural product. <![CDATA[Rhenium(I) Polypyridine Complexes as Luminescence-Based Sensors for the BSA Protein]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100179&lng=pt&nrm=iso&tlng=pt The binding interaction of rhenium(I) complexes fac-[Re(CO)3(NN)(py)]+, py = pyridine and NN = 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (ph2phen) or 4,7-dichloro-1,10-phenanthroline (Cl2phen), and bovine serum albumin (BSA) was investigated at physiological pH using emission intensity variation and circular dichroism (CD) spectroscopy. The photophysical investigations showed that in the presence of BSA, the metal-to-ligand-charge transfer (3MLCT) emission of the rhenium(I) complexes was quenched due to entrapment of the complex within the protein environment. Additionally, high Stern-Volmer (KSV) and binding (Kb) constants were determined from luminescence data, revealing the occurrence of a strong interaction and/or association. The differences in KSV values can be tentatively associated with an electron-withdrawing constant (σ) defined by Hammett equation. The CD results showed that the extent of α-helicity of the BSA decreased upon the addition of rhenium complexes, which provided further support for the interaction of rhenium(I) complexes and the protein. <![CDATA[Simultaneous Determination of Herbicides in Rice by QuEChERS and LC-MS/MS Using Matrix-Matched Calibration]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100186&lng=pt&nrm=iso&tlng=pt The main objective of the present work was to validate a chromatographic method to determine herbicides commonly applied in the irrigated rice farming. For this, matrix-matched calibration was employed along with the extraction and clean-up of the samples by quick, easy, cheap, effective, rugged and safe (QuEChERS) method and determination of the analytes by high performance liquid chromatography tandem mass spectrometry (LC-MS/MS) with electrospray ionization in the positive mode. By this method, it was possible to achieve the ionization and detection of a total of 18 herbicides, with quantification of 12 of them. The method presented adequate precision and accuracy according to the European Commission and the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines for analytes in low concentrations. The limits of quantification ranged from 0.015 μg g-1 for oxadiazon to 0.165 μg g-1 for imazapyr. The method showed good linearity with R2&gt; 0.99 and recovery values from 92 to 103%. The proposed protocol is adequate for monitoring bispyribac-sodium, cyclosulfamuron, cycloxydim, clomazone, ethoxysulfuron, fenoxaprop-p-ethyl, imazapic, imazapyr, imazethapyr, metsulfuron-methyl, oxadiazon and thiobencarb in rice grains in concentrations up to 109 times lower than the maximum residue limits established by the Brazilian Health Surveillance Agency (ANVISA) for these compounds in rice samples. <![CDATA[Synthesis and Characterization of New Diazenecarboxamide Ligands Using a Selective Adduct Formation with B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100194&lng=pt&nrm=iso&tlng=pt The synthesis and structure of new N-(2,6-diisopropylphenyl)-2-phenyldiazenecarboxamide (L2) and N-(2,6-diisopropylphenyl)-2 (perfluorophenyl) diazenecarboxamide (L3) ligands are described. The subsequent reactions of ligands L1, L2 and L3 with trispentafluorophenylboron gave rise to new adducts (A1), (A2) and (A3), where B(C6F5)3 is coordinated to the carbonyl group. New ligands and adducts are characterized by nuclear magnetic resonance (NMR), infrared (IR), and elemental analysis techniques. The crystal structures of all compounds are obtained and described. <![CDATA[Optimization of Reaction Conditions for Cyclohexane to Cyclohexanone with t-Butylhydroperoxide Over CuCl<sub>2</sub> Loaded with Activated Carbon]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100202&lng=pt&nrm=iso&tlng=pt Catalytic oxidation of hydrocarbons can be performed efficiently in the presence of tert- butylhydroperoxide (TBHP) under a low-valent transition metal as the catalyst. CuCl2 loaded with activated carbon had synthesized and characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX), and then utilized as a catalyst for the oxidation of cyclohexane with molecular oxygen as the oxidant and the TBHP as the pro-oxidant under various conditions. The possible reaction mechanism was discussed and the effects of different factors on the oxidation of cyclohexane were investigated. Reaction conditions including catalyst type, oxidant, reaction time, reaction temperature, TBHP amount, solvent type and solvent amount were systematically optimized in order to achieve the highest conversion of cyclohexane and highest selectivity of cyclohexanone. Various other alkanes exhibited higher catalytic activity under the optimal conditions. <![CDATA[Removal of Chromium(VI) from Industrial Effluents Through Supported Liquid Membrane Using Trioctylphosphine Oxide as a Carrier]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100209&lng=pt&nrm=iso&tlng=pt The present study describes extraction of chromium(VI) through supported liquid membrane (SLM), Celgard 2400, which was impregnated with trioctylphosphine oxide (TOPO) dissolved in toluene. The stripping phase was comprised of diphenylcarbazide (DPC) in sulfuric acid (H2SO4) whereas the feed phase consists of potassium dichromate (K2Cr2O7) and hydrogen peroxide (H2O2). The effects of concentrations of chromium, TOPO, DPC, and H2SO4 have been studied in order to evaluate the transport efficiency of chromium(VI) ion. The optimum experimental conditions for the chromium(VI) extraction were established as follows: 19.2 × 10−4 mol L-1 chromium ion, 1.5 mol L-1 H2O2 concentration in the feed phase, 0.1 mol L-1 TOPO concentration in the membrane phase and 0.001 mol L-1 DPC and 1.5 mol L-1 H2SO4 as stripping phase. The measurements of percent recovery, distribution coefficient, flux and permeability were made at the given optimized conditions. The extraction time and membrane stability were also investigated. Extraction efficiency of 80% was recorded in 180 min and the SLM system was found stable up to 10 days. The optimized SLM system was then applied on the paint industry wastewater; about 80% of chromium(VI) was successfully removed from the wastewater. <![CDATA[Application of a 3<sup>3</sup> Box-Behnken Design to Optimize the Extraction of Eleven Fluoroquinolones from Poultry Muscle and Kidney Using a QuEChERS Approach via Liquid Chromatography Tandem Mass Spectrometry: the Easy Use of Microsoft Excel<sup>®</sup> in Multivariate Analysis]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016000100221&lng=pt&nrm=iso&tlng=pt This work presents an optimization of a quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction approach of eleven fluoroquinolones in poultry muscle and kidney using a 33 Box-Behnken factorial design. All the data treatment was performed using Microsoft Excel® 2010. The suitability of the developed method was confirmed by two proficiency tests for ciprofloxacin and enrofloxacin.