Characterization of interfering effects in the determination of molybdenum by atomic absorption spectrometry

The effect of anions on molybdenum absorbance depends on the pH; low pH causes the formation of iso- or heteropoly anions which change the atomization process in the flame. Organic ligands also depress the release of molybdenum atoms but cyanide radicals in the flame scavenge, e.g., OH radicals from such ligands and prevent their depressive effect. Certain cations (La, Ce, Mg, Ca, Sr and Ba) appear to form spinels; boric acid minimizes this effect.     

Photocatalytic effect of nano-TiO<Subscript>2</Subscript> loaded cement on dye decolorization and <Emphasis Type="Italic">Escherichia coli</Emphasis> inactivation under UV irradiation

In the present study, titanium dioxide (TiO₂) nano-particles were synthesized by sol–gel technique and then used to provide nano-TiO₂ loaded cement samples at 1, 5, and 10 wt% for investigation of Malachite green pigment decomposition and Escherichia coli inactivation under UV irradiation. Surveys conducted on the synthesized TiO₂ nano-particles showed a 100 % anatase phase with a mean particle size of 66.5 nm, surface area of 64.352 m² g^?1, and a porosity volume of 0.1278 cm³ g^?1. Cement samples containing this catalyst exhibited stronger photocatalytic properties as compared to the same amount of pure catalyst. Considering both photocatalytic performance and cost of catalyst, 5 wt% titanium dioxide was suggested to be added to cement. By addition of 1 wt% polycarboxylic copolymer as super-plasticizer to the cement paste, the photocatalytic sample activities were reinforced so that a similar performance could be obtained at 1 wt% catalyst as compared to 5 wt% catalyst without super-plasticizer.     

Some Characterizations of Integral Operators Associated with Certain Classes of <Emphasis Type="Italic">p</Emphasis>-Valent Functions Defined by the Srivastava–Saigo–Owa Fractional Differintegral Operator

The purpose of this paper is to introduce new integral operators associated with Srivastava–Saigo–Owa fractional differintegral operator. We investigate some properties for the integral operators \({\mathcal {F}}_{p,\eta ,\mu }^{\lambda ,\delta }(z)\) and \({\mathcal {G}}_{p,\eta ,\mu }^{\lambda ,\delta }(z)\) to be in the classes \({\mathcal {R}}_{k}^{\zeta }\left( p,\rho \right) \) and \({\mathcal {V}}_{k}^{\zeta }\left( p,\rho \right) \).     

Development and Validation of LC Method for Simultaneous Determination of Two Binary Mixtures Containing Indapamide

A new sensitive, simple, rapid, and precise RP LC method with hydrochlorothiazide as internal standard has been developed for resolving two binary mixtures, perindopril with indapamide and captopril with indapamide, in pharmaceutical formulations. The drugs were separated at room temperature on a 250 mm × 4.6 mm, 5-μm particle, cyanopropyl column with 10 mm KH₂PO₄, pH 6.0-methanol 55:45 (v/v) as mobile phase at a flow rate of 1 mL min^?1. Detection was at 210 nm. Factors affecting the separation process were studied and optimized. The linearity, accuracy, and precision of the method were good, and the method was successfully applied to the determination of the two binary combinations in synthetic mixtures and commercial pharmaceutical products.     

Application of a Validated, Stability-Indicating LC Method to Stress Degradation Studies of Ramipril and Moexipril.HCl

A stability-indicating reversed-phase liquid chromatographic (RPLC) method has been established for analysis of ramipril (RAM) and moexipril hydrochloride (MOEX.HCl) in the presence of the degradation products generated in studies of forced decomposition. The drug substances were subjected to stress by hydrolysis (0.1 m NaOH and 0.1 m HCl), oxidation (30% H₂O₂), photolysis (254 nm), and thermal treatment (80 °C). The drugs were degraded under basic and acidic conditions and by thermal treatment but were stable under other stress conditions investigated. Successful separation of the drugs from the degradation products was achieved on a cyanopropyl column with 40:60 (v/v) aqueous 0.01 m ammonium acetate buffer (pH 6)–methanol as mobile phase at a flow rate of 1 mL min⁻¹. Detection was by UV absorption at 210 nm. Response was a linear function of concentration over the range 5–50 μg mL⁻¹ (r > 0.9995), with limits of detection and quantitation (LOD and LOQ) of 0.04 and 0.09 μg mL⁻¹, respectively, for RAM and 0.014 and 0.32 μg mL⁻¹, respectively, for moexipril. The method was validated for specificity, selectivity, solution stability, accuracy, and precision. Statistical analysis proved the method enabled reproducible and selective quantification of RAM and MOEX as the bulk drug and in pharmaceutical preparations. Because the method effectively separates the drugs from their degradation products, it can be used as stability-indicating.     

Synthesis and exploring the excited-state PES of photochromic hydrogen bond-assembled [2]rotaxane based on 1,3-Diazabicyclo-[3.1.0]hex-3-enes

Here, the synthesis of photochromic hydrogen bond-assembled [2]rotaxanes using bis-fumarate as a thread for the first time is reported. In fact, photochromic 1,3-diazabicyclo[3.1.0]hex-3-ene moieties were used as stoppers and two-atom spacers managed good binding sites for the tetralactam macrocycles in clipping reactions. Moreover, the yields of photochromic [2]rotaxanes highly depended on the NO₂ substituent stoppers. While the thread with a para –NO₂ substituent as stopper units was shown to be an excellent template for the synthesis of photochromic [2]rotaxanes. The structures of the [2]rotaxanes are established clearly in solution by chemical shifts of the ¹H ¹³C NMR signals and UV–Vis spectra. A pronounced bathochromic shift was occurred in the excitation wavelength of photochoromic [2]rotaxanes compared with the absorption band of photochromic threads. Therefore, these organizations can be applied in light-driven molecular switches and motors. The reversible transformation of trans and cis geometric photoisomers under UV radiation was identified. In other efforts, the possibility of the process of trans to cis interconversion of the fumarate linker under UV irradiation has been examined computationally and it has appeared that it may cause the transverse of the bis-fumarate linker inside the tetralactam macrocycle to some extent.

     

DNA-Binding Capabilities and Anticancer Activities of Ruthenium(II) Cymene Complexes with (Poly)cyclic Aromatic Diamine Ligands

Ruthenium(II) arene complexes of the general formula [RuCl(η⁶-p-cymene)(diamine)]PF₆ (diamine = 1,2-diaminobenzene (1), 2,3-diaminonaphthalene (2), 9,10-diaminophenanthrene (3), 2,3-diaminophenazine (4), and 1,2-diaminoanthraquinone (5) were synthesized. Chloro/aqua exchange was evaluated experimentally for complexes 1 and 2. The exchange process was investigated theoretically for all complexes, revealing relatively fast exchange with no significant influence from the polycyclic aromatic diamines. The calf thymus DNA (CT-DNA) binding of the complexes increased dramatically upon extending the aromatic component of the diamines, as evaluated by changes in absorption spectra upon titration with different concentrations of CT-DNA. An intercalation binding mode was established for the complexes using the increase in the relative viscosity of the CT-DNA following addition of complexes 1 and 2. Theoretical studies showed strong preference for replacement of water by guanine for all the complexes, and relatively strong Ru–N_guanine bonds. The plane of the aromatic systems can assume angles that support non-classical interactions with the DNA and covalent binding, leading to higher binding affinities. The ruthenium arenes illustrated in this study have promising anticancer activities, with the half maximal inhibitory concentration (IC₅₀) values comparable to or better than cisplatin against three cell lines.     

Highly Efficient Methylene Blue Dye Removal by Nickel Molybdate Nanosorbent

Removing methylene blue (MB) dye from aqueous solutions was examined by the use of nickel molybdate (α-NiMoO₄) as an adsorbent produced by an uncomplicated, rapid, and cost-effective method. Different results were produced by varying different parameters such as the pH, the adsorbent dose, the temperature, the contact time, and the initial dye concentration. Adsorbent dose and pH had a major removal effect on MB. Interestingly, a lower amount of adsorbent dose caused greater MB removal. The amount of removal gained was efficient and reached a 99% level with an initial methylene blue solution concentration of ≤160 ppm at pH 11. The kinetic studies indicated that the pseudo-second-order kinetic model relates very well with that of the obtained experimental results. The thermodynamic studies showed that removing the MB dye was favorable, spontaneous, and endothermic. Impressively, the highest quantity of removal amount of MB dye was 16,863 mg/g, as shown by the Langmuir model. The thermal regeneration tests revealed that the efficiency of removing MB (11,608 mg/g) was retained following three continuous rounds of recycled adsorbents. Adsorption of MB onto α-NiMoO₄ nanoparticles and its regeneration were confirmed by Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) analysis. The results indicated that α-NiMoO₄ nanosorbent is an outstanding and strong candidate that can be used for removing the maximum capacity of MB dye in wastewater.     

An attempt towards coordination supramolecularity from Mn(II), Ni(II) and Cd(II) with a new hexadentate [N4O2] symmetrical Schiff base ligand: Syntheses,crystal structures,electrical conductivity and optical properties

To explore the influence of non-covalent weak force interactions, mainly exerted by carboxylic groups, on the formation of supramolecular architectures of transition metal complexes and their electrical conduction processes, a new symmetrical [N₄O₂] hexadentate Schiff base ligand, 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H₄fsatrien, and its complexes of Ni(II), Cd(II) and Mn(II) have been synthesized using in situ condensation of the ligand components in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV–Vis, NMR, ESR, molar conductivity and magnetic measurements. The crystal structures of all the complexes have been determined by a single crystal X-ray diffraction study. The 1-D, 2-D and 3-D networks of the complexes are formed by π–π stacking, C–H?π interactions and mono or bifurcated H-bonding. The electronic structures of the complexes have been examined using the DFT method. Solid-state properties (e.g. electrical conductivity at different temperatures and optical properties) of the Ni(II) and Mn(II) complexes have also been studied and, depending on the temperature, the conductivity of the complexes is found to be insulating and semiconducting (intrinsic and extrinsic) in nature. The optical band gap (E_gd) of complexes (1) and (3) is found to be 2.57 and 2.30 eV, respectively.