Synthesis, thermal stability, electronic features, and antimicrobial activity of phenolic azo dyes and their Ni(II) and Cu(II) complexes

Four water soluble azo dyes, 4-(isopropyl)-2-[(E)-(4-chlorophenyl)diazenyl]phenol (L ¹), 4-(isopropyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L²), 4-(sec-butyl)-2-[(E)-(4-chlorophenyl) diazenyl]phenol (L ³), 4-(sec-butyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L ⁴), and their Cu(II) and Ni(II) complexes were synthesized and characterized using spectroscopic methods. Examination of their thermal stability revealed similar decomposition temperature of approximately 260–300°C and that they were more thermally stable than their metal complexes. Ni(II) complexes of ligands L² and L⁴ were more stable than the other coordination compounds. Among the synthesized ligands, L² and the complexes Cu(L³)₂ and Ni(L⁴)₂ showed both antimicrobial and antifungal activity. However, the other ligands and the complexes were poorly active against selected microorganisms.     

The uranium recovery from aqueous solutions using amidoxime modified cellulose derivatives. IV. Recovery of uranium by amidoximated hydroxypropyl methylcellulose

Amidoxime modified hydroxypropyl methylcellulose (HPMC) films (HPMC-g-AO) were used for the recovery of uranium from aqueous solutions by a complexation process. The adsorption experiments were carried out by immersion of a certain amount of films in UO₂ ²⁺ solutions (resultant pH 4.1) ranging in concentration from 100 to 1,000 ppm. The effect of temperature (25–50 °C) on the adsorption capacity of HPMC-g-AO was investigated at the optimized time. The adsorption kinetics and the thermodynamics as well as the adsorption capacity of HPMC-g-AO films were investigated. The adsorption capacity was found as 765 mg UO₂ ²⁺/g dry film. The kinetic and the thermodynamic parameters (i.e. activation energy, enthalpy, entropy and Gibbs free energy) for the interaction of UO₂ ²⁺ with HPMC-g-AO were calculated based on known basic relations. The results showed that adsorption occurred through strong electrostatic interactions with an enthalpy of ?36.5 kJ/mol. The desorption of UO₂ ²⁺ were investigated using different desorption agents such as EDTA, HCl, NaHCO₃, and NaOH. After the 2 weeks treatment period, the highest desorption yield were found as 23 % with NaHCO₃.     

Characterization and in vitro release kinetics of chitosan based biocomposites from Scotch Bonnets

The main aim of this study is to formulate the combination of the bioactive composite containing chitosan/β -tricalcium phosphate (CH/β-TCP) as potential drug delivery platforms for the sustained release of antibiotics. Herein the mode of amoxicillin (AMX) maintained in the β-TCP/chitosan composite was characterized using XRD, FT-IR to confirm the phase purity and functional groups. SEM was used to examine the size and shape of particles. The SEM images of the biocomposites after drug release confirmed that they are biodegradable. In vitro drug release experiments in PBS (pH 7.4) revealed a sustained release profile in a neutral medium. Drug release profiles were evaluated according to five different kinetic models including Zero Order, First Order, Higuchi, Hixon Crowel, and Korsmeyer-Peppas. The release profile was best expressed by the Korsmeyer Peppas model because the results showed high linearity. Overall, the positive effect of chitosan coating on the drug elution profile of β-TCP as carriers for the controlled delivery of antibiotics was regarded as biocompatible for the controlled drug delivery system.     

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk,egg, fish,bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH₃ (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L^?1 for marbofloxacin, and 1.09 µg L^?1 for enoxacin; 3.23 × 10^?3 µg L^?1 for ofloxacin; 8.39 × 10^?3 µg L^?1 for ciprofloxacin; and 19.50 × 10^?3 µg L^?1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%.     

Separation and preconcentration of Pb(II) using ionic liquid-modified silica and its determination by flame atomic absorption spectrometry

A new method based on microcolumn packed with ionic liquid-modified silica combined with flame atomic absorption spectrometry has been developed for the determination of lead in environmental samples. Several factors influencing the preconcentration efficiency of lead and its subsequent determination, such as pH of the sample, flow rate, mass of ionic liquid, and interfering effect, have been investigated. Lead could be quantitatively retained by ionic liquid-modified silica in the pH range of 5-7, and then eluted completely with 3.0 mL 1.0 mol L⁻¹ HCl. The detection limit of this method for lead was 0.7 μg L⁻¹ with preconcentration factor of 185, and the relative standard deviation (RSD) was 4.2% at 0.1 μg mL⁻¹ Pb(II). This method has been applied for the determination of trace amount of lead in NIST standard reference material 2709 (San Joaquin Soil) and river water samples with satisfactory results.     

A fluorescent chemical sensor for ethanol determination in alcoholic beverages

A sensor for ethanol is described that is based on the fluorescent probe 5,10,15,20-tetraphenyl porphyrin (TPP). Response is based on the quenching of the fluorescence of TPP by ethanol as a result of electrostatic attraction. The sensor linearly responds to ethanol in the concentration range from 1 to 75 vol.% and was applied to the determination of ethanol in various kinds of wines and whisky.     

über Metallkomplexe der Heteroarylformazane

Two new heteroarylformazans with two complex forming carboxy groups in the ortho position relative to the formazan chain have been synthesized. These compounds form complexes with uranyl, cobalt and nickel ions. The ratio metal/formazan of these complexes has been investigated.     

Oscillatory and Periodic Solutions of Impulsive Differential Equations with Piecewise Constant Argument

We study the existence of oscillatory and periodic solutions of a class of first order scalar impulsive delay differential equations with piecewise constant argument.     

Elucidating the Stereochemistry of Enzymatic Benzylsuccinate Synthesis with Chirally Labeled Toluene

Benzylsuccinate synthase is a glycyl radical enzyme that initiates anaerobic toluene metabolism by adding fumarate to the methyl group of toluene to yield (R)‐benzylsuccinate. To investigate whether the reaction occurs with retention or inversion of configuration at the methyl group of toluene, we synthesized both enantiomers of chiral toluene with all three H isotopes in their methyl groups. The chiral toluenes were converted into benzylsuccinates preferentially containing ²H and ³H at their benzylic C atoms, owing to a kinetic isotope effect favoring hydrogen abstraction from the methyl groups. The configuration of the products was analyzed by enzymatic CoA‐thioester synthesis and stereospecific oxidation using enzymes involved in benzylsuccinate degradation. Assessment of the configurations of the benzylsuccinate isomers based on loss or retention of tritium showed that inversion of configuration at the methyl group occurs when the chiral toluenes react with fumarate.