Batch‐injection versus Flow‐injection Analysis Using Screen‐printed Electrodes: Determination of Ciprofloxacin in Pharmaceutical Formulations

This article highlights the potential use of multi‐walled carbon‐nanotube modified screen‐printed electrodes (SPEs) for the amperometric sensing of ciprofloxacin and compares the association of batch‐injection analysis (BIA) and flow‐injection analysis (FIA) with amperometric detection. Both analytical systems provided precise (RSD<5 %) and sensitive determination of ciprofloxacin (LOD<0.1 μmol L^?1) within wide linear range (up to 200 μmol L^?1). Accuracy of both methods was attested by recovery values (93–107 %) and comparison with capillary electrophoresis. The BIA system is completely portable (especially due to association with SPEs) and provided faster analyses (130 h^?1) and more sensitive detection than the FIA system due to the higher flow rates of injection.     

Synthesis,spectroscopic characterization and DFT study of dinuclear ruthenium sawhorse-type complexes derived from the reaction of trinuclear aggregates and (Z)-5-arylidenerhodanines

The synthesis of dinuclear ruthenium sawhorse-type complexes [Ru₂(μ-ArCH:Rhod)₂(CO)₄]_n 12a–e and [Ru₂(ArCH:Rhod)₂(μ-ArCH:Rhod)₂(CO)₄] 13a–e through reaction of [Ru₃(CO)₁₀(NCMe)₂] and [Ru₃(CO)₁₂] and the corresponding (Z)-5-arylidenerhodanines (ArCH:Rhod) 10a–e, respectively, are reported. These complexes are arranged in a sawhorse structure in which two bridged (Z)-5-arylidenerhodanines coordinate to the metals using sulfur and nitrogen of the rhodanine ring. A Density Functional Theory method was used to gain insight into the polymerization process by calculating dimerization Gibbs energies (ΔG_dim). Values between ?10.7 and ?5.3 kcal mol^?1 indicate that dimerization is a spontaneous process. A reaction pathway for formation of the sawhorse compounds [Ru₂(μ-ArCH:Rhod)₂(CO)₄] was calculated and the rate-determining step for the mechanism is coordination of a second (Z)-5-arylidenerhodanine ligand with activation energies between 41.1 and 47.8 kcal mol^?1. In order to understand the apparent thermodynamic favorability of the fragmentation step, we calculated the fragmentation energy (ΔE_Frag) for the key intermediate and its energetic contributors, the interaction energy, ΔE_int and the reorganization energy, ΔE_reorg. Low values of ΔE_Frag imply that the fragmentation is thermodynamically facile. Large values of ΔE_int are countered by opposite and large values of ΔE_reorg which indicate that the cleavage of the trimetallic intermediate aggregate is determined by the nature of the ligand and the balance between its interaction with the metal and the extent of structural reorganization.     

Electron correlation in the interacting quantum atoms partition via coupled‐cluster lagrangian densities

The electronic energy partition established by the Interacting Quantum Atoms (IQA) approach is an important method of wavefunction analyses which has yielded valuable insights about different phenomena in physical chemistry. Most of the IQA applications have relied upon approximations, which do not include either dynamical correlation (DC) such as Hartree‐Fock (HF) or external DC like CASSCF theory. Recently, DC was included in the IQA method by means of HF/Coupled‐Cluster (CC) transition densities (Chávez‐Calvillo et al., Comput. Theory Chem. 2015, 1053, 90). Despite the potential utility of this approach, it has a few drawbacks, for example, it is not consistent with the calculation of CC properties different from the total electronic energy. To improve this situation, we have implemented the IQA energy partition based on CC Lagrangian one‐ and two‐electron orbital density matrices. The development presented in this article is tested and illustrated with the H₂, LiH, H₂O, H₂S, N₂, and CO molecules for which the IQA results obtained under the consideration of (i) the CC Lagrangian, (ii) HF/CC transition densities, and (iii) HF are critically analyzed and compared. Additionally, the effect of the DC in the different components of the electronic energy in the formation of the T‐shaped (H₂)₂ van der Waals cluster and the bimolecular nucleophilic substitution between F^– and CH₃F is examined. We anticipate that the approach put forward in this article will provide new understandings on subjects in physical chemistry wherein DC plays a crucial role like molecular interactions along with chemical bonding and reactivity. © 2016 Wiley Periodicals, Inc.     

Inhibition of cell proliferation,invasion and migration by the cardenolides digitoxigenin monodigitoxoside and convallatoxin in human lung cancer cell line

Cardiac glycosides consist of a large family of naturally derived compounds that are clinically used to treat congestive heart failure, and also present anticancer properties. In this study, the cytotoxic effects of two cardenolides, digitoxigenin monodigitoxoside (DGX) and convallatoxin (CON) were screened in four human tumour cell lines. Both compounds showed anti-proliferative effects in all tumour cells, at nanomolar concentrations. Since the human lung cancer cell line A549 was the most sensitive, we investigated the anti-proliferative, anti-migratory and anti-invasive effects of these cardenolides. DGX and CON reduced A549 cell migration, being able to reduce more than 90% of cell invasion. Their effects on the expression of key regulators of metastatic mechanism showed decreased levels of MMP-2, MMP-9 and p-FAK. Both compounds also presented low toxicity for healthy cells. Finally, this work provides the first insights into the effects of these cardenolides on key steps of lung cancer metastasis.     

Combination of sonication and heating for metal extraction from inorganic fertilizers prior to microwave-induced plasma spectrometry determinations

This work reports a fast and efficient method for metal extraction in inorganic fertilizers by combining heating and sonication using an ultrasonic bath. Microwave-induced plasma optical emission spectrometry (MIP OES) was applied for the determination of Cd, Cu, Cr, Mn, Pb, and Zn in the extracts. Higher efficiency of metal extraction (∼100% for all metals except to Cd) was obtained for the treatment of 150 mg of fertilizer with 4 mL of 50% (v/v) HCl sonicated for 10 min and heating at 85 °C. Extractions applying only heating did not provide satisfactory results. The proposed procedure is simple and contributes to reduced production of waste in comparison to the official method.     

Chemical Modification in the Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities

Chemical modification of enzymes and immobilization used to be considered as separate ways to improve enzyme properties. This review shows how the coupled use of both tools may greatly improve the final biocatalyst performance. Chemical modification of a previously immobilized enzyme is far simpler and easier to control than the modification of the free enzyme. Moreover, if protein modification is performed to improve its immobilization (enriching the enzyme in reactive groups), the final features of the immobilized enzyme may be greatly improved. Chemical modification may be directed to improve enzyme stability, but also to improve selectivity, specificity, activity, and even cell penetrability. Coupling of immobilization and chemical modification with site‐directed mutagenesis is a powerful instrument to obtain fully controlled modification. Some new ideas such as photoreceptive enzyme modifiers that change their physical properties under UV exposition are discussed.     

The regiospecific lithiation of aromatic acetals

The dimethylacetal of benzaldehyde and some 3, 3,4 and 3,4,5 oxygenated derivatives thereof are regiospecifically deprotonated at the 2-position by alkyl lithiums. The resulting aryl lithiums provide various 2-substituted benzaldehydes in moderate to excellent yields.     

Potentiometric Stripping Analysis for Simultaneous Determination of Copper and Lead in Lubricating Oils After Total Digestion in a Focused Microwave-Assisted Oven

The determination of metals in lubricating oil has been used as an important means of preventing components failures, to provide environmental information, and to solve criminal issues. In this study derivative potentiometric stripping analysis (DPSA) was used for the simultaneous determination of copper and lead in lubricating oils of vehicular engines. The samples were completely digested in a focused microwave-assisted oven using a powerful oxidant mixture (HNO₃, H₂SO₄, H₂O₂). The optimized heating program to digest about 1mL of lubricating oil takes 45minutes. The residual carbon content after digestion was below 0.3%m/m for all samples. Copper and lead were also determined by graphite furnace atomic absorption spectrometry (GFAAS), and the results obtained were in good agreement with those obtained by electrochemical measurements. Recoveries of 94–109 and 93–103%, for copper and lead, respectively, were obtained for new and used lubricating oil samples.     

Catalytic properties of iron oxides impregnated with copper acetate

Textural and catalytic properties of iron oxides impregnated with copper acetate were investigated. In order to get satisfactory performance in the high temperature shift reaction, 4 impregnation hours are necessary.     

A new and efficient N-alkylation procedure for semicarbazides/semicarbazones derivatives

An easy to perform and regioselective synthesis of N-alkyl hydrazones/hydrazides is described, which uses an aprotic medium with kinetic control. This procedure produced the desired monoalkylated or dialkylated amines with excellent yields and selectivities.