Ultrasensitive Simultaneous Quantification of Nanomolar Level of Cd and Zn by Cathodic Adsorptive Stripping Voltammetry in Some Real Samples

A novel, simple and sensitive adsorptive stripping voltammetry method was developed for simultaneous determination of Cd and Zn using N‐Nitrozo‐N‐phenylhydroxylamine (Cupferron) as a selective complexing agent. Cadmium and zinc metals gave peaks that were distinctly separated by 450–1200 mV, allowing their determination over a wide range of concentrations. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The detection limits were 0.058 ng/mL for Zn and 0.092 ng/mL for Cd, and the RSD at a concentration level of 50 ppb, were 1.8–2.1 % for both zinc and cadmium, respectively. The method was applied to the determination of cadmium and zinc in blood, drug, food and water samples with the satisfactory results.     

Macrocyclic host cyclophosphazenes from aminolysis of N3P3CI6 by bis-(2-ortho-aminophenoxyethyl)ether

Aminolysis of N₃P₃CI₆ by an oxodiamine, bis-(2-ortho-aminophenoxyethyl) ether, has been carried out under various experimental conditions and new products with different architectures have been obtained. The reaction in diethyl ether when using a Na₂CO₃-water interface process gives the mono-BINO as major product. Reaction on Al₂O₃/KOH leads to the spirocyclic compound, while, when the reaction is carried out in toluene in the presence of NEt₃, a mixture of mono- and di-BINO products are obtained. These new products have been characterized by IR, ¹H and ³¹P NMR spectroscopy.      

Simultaneous spectrofluorimetric determination of levodopa and propranolol in urine using feed-forward neural networks assisted by principal component analysis

The simultaneous determination of levodopa (LD) and propranolol (PRO) using fluorescence spectrometric technique is described. The method involves measuring the natural fluorescence of these drugs in the micellar media of sodium dodecyl sulfate (SDS) using principal component analysis-feed-forward neural networks (PC-FFNNs). Experimental conditions such as effect of pH and SDS concentration were optimized. Under the optimum conditions, the linear determination ranges of LD and PRO are 2.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ and 3.6 × 10⁻⁹ to 1.8 × 10⁻⁶ mol L⁻¹, respectively. A set of synthetic binary mixtures of LD and PRO was prepared and their concentrations were predicted by the proposed method. Satisfactory results were obtained by the combination of fluorescence technique with chemometrics methods. The method was successfully applied to the determination of LD and PRO in tap water and in urine samples.     

Cup-shaped E,E-stilbenophane: synthesis,crystal structure and supramolecular chemistry

A new E,E-stilbenophane was synthesised and characterised. The crystal structure of this cyclophane shows that this molecule has a cup-shaped structure, which hosts a phenyl ring of neighbouring molecule as guest in its cavity with a π–π distance of about 3.7 Å. Moreover, the NMR spectra and theoretical analysis (gauge-independent atomic orbitals (GIAO) and quantum theory of atoms in molecules (QTAIM)) suggest that the silver recognition by E,E-stilbenophane host molecules is based on cation–π interactions in which the π-electrons of the double bonds play a major role.     

A novel covalent functionalisation of poly (styrene-alt-maleic anhydride) with 4-amino benzo-9-crown-3 ether

The grafting of 4-amino benzo-9-crown-3 ether to poly (styrene-alt-maleic anhydride) has been described. The covalent grafting of crown ether has led to a considerable increase in the solubility of polymer in organic solvents such as dimethyl sulphoxide, dimethylformamide and tetrahydrofuran. The highest solubility was attained in DMF and DMSO. The covalently bonded 4-benzo-9-crown-3 ether allowed the hosting of Li⁺. The covalently grafted crown ether to polymer was identified by infrared spectroscopy and thermogravimetric analysis methods.     

Thermoanalytical study of linkage isomerism in coordination compounds: Part I. Reinvestigation of thermodynamic and thermokinetic of solid state interconversion of nitrito (ONO) and nitro (NO2) isomers of pentaaminecobalt(III) chloride by means of DSC

Solid state thermal isomerization of [Co(NH₃)₅(ONO)]Cl₂ (nitrito isomer) to [Co(NH₃)₅(NO₂)]Cl₂ (nitro isomer) and reverse reaction were investigated by non-isothermal differential scanning calorimetry (DSC) and found to be essentially an equilibrium process. The interconversions are accelerated at above 65 °C and reach to equilibrium state at about 155 °C. After establishment of the equilibrium the relative amounts of two isomers at any temperature are governed by Gibbs free energy relationship. The experimental enthalpy changes of isomerization of pure nitrito and nitro solid samples to the equilibrium state are −4.67 (±0.19) and 0.99 (±0.05) kJ mol⁻¹, respectively. From these values, total enthalpy change was calculated as: ΔH°=−5.66(±0.20) kJ mol⁻¹. Using Gibbs free energy relationship, equilibrium constant, total free energy and entropy changes were estimated at 60 °C as: K=7.72(±0.8),  kJ mol⁻¹ and  J K⁻¹ mol⁻¹.An initial rate method has been developed to determine the kinetic parameters of these reactions from non-isothermal DSC data. Both nitro to nitrito and reverse reactions obey first order kinetic law in solid state. Estimated activation parameters of forward and reverse paths at 60 °C are , , and , respectively. The negative activation entropy of both directions support the intramolecular mechanism of isomerization, including formation of a seven coordinate transition state, which formerly suggested based on spectral and X-ray methods.     

Ion pairing, H-bonding, and π–π interactions in copper(II) complex-organo-networks derived from a proton-transfer compound of the 1,10-phenanthroline-2,9-dicarboxylic acid

The one-pot reaction between the novel proton transfer compound (pydaH₂)²⁺(phendc)²⁻, LH₂, and Cu(II) afforded the compounds (pydaH)₂[Cu(phendc)₂]·10H₂O, 1, and (pydaH)₂[Cu(phendc)(phendcH)]₂·5H₂O, 2, where pyda=2,6-diaminopyridine, and phendcH₂=1,10-phenanthroline-2,9-dicarboxylic acid. The single crystal X-ray diffraction analysis of 1 and 2 revealed that these are two novel self-assembled 3D Cu(II) complex-organo-networks, in which (pydaH)⁺ ions and [Cu(phendc)₂]²⁻ or complex units are held together by ion pairing, H-bonding, and π–π interactions. Magnetic measurements over the temperature range 1.8–310 K revealed no significant magnetic coupling between Cu(II) centers in 1 or 2.     

DFT studies on the tetranuclear cubane complex [Ni4(ampd)4(Cl4)]·MeCN

Density functional theory (DFT) is used to investigate the structural properties of Ni(II) cubane [Ni₄(ampdH)₄Cl₄]·MeCN. The structural features and ground state geometry calculations are computed at the B3LYP/6-31G* (LANL2DZ) level of theory. We shed light on the highest occupied molecular orbital and lowest unoccupied molecular orbital. The absorption spectrum is calculated using time-dependent DFT. The absorption wavelengths are calculated using different functionals, i.e., pw91pw91, B3LYP, BHandHLYP, CAM-B3LYP, LC-BLYP, and M06. The LC-BLYP is in good agreement with the experimental data.     

Skin‐worn Soft Microfluidic Potentiometric Detection System

A flexible skin‐mounted microfluidic potentiometric device for simultaneous electrochemical monitoring of sodium and potassium in sweat is presented. The wearable device allows efficient natural sweat pumping to the potentiometric detection chamber, containing solid‐contact ion‐selective Na⁺ and K⁺ electrodes, during exercise activity. The fabricated microchip electrolyte‐sensing device displays good analytical performance and addresses sweat mixing and carry‐over issues of early epidermal potentiometric sensors. Such soft skin‐worn microchip platform integrates potentiometric measurement, microfluidic technologies with flexible electronics for real‐time wireless data transmission to mobile devices. The new fully integrated microfluidic electrolyte‐detection device paves the way for practical fitness and health monitoring applications.