The use of ultrasonic treatment for improvement of metrological performance of sorption atomic absorption determination of lead(II) and cadmium(II) traces

The optimal parameters for ultrasonic treatment (frequency 200–300 kHz, intensity 2–4 W cm^?2) were obtained to intensify Pb(II) and Cd(II) sorption concentration by carbon sorbent from apricot pit. The combined action of ultrasonic frequency of 18 kHz and 1 MHz on concentrate slurry increases its sedimentation stability from 3 to 180 minutes and decreases S_r value up to 7% at Pb(II), Cd(II) hybrid sorption atomic absorption determination in natural waters, brines, common salt.      

Metals content of soil,leaves and wild fruit from Serbia

The concentrations of Zn, Mn, Fe, Pb, Ni, Cu and Cd in soil, leaves and edible wild fruit (Crataegus laevigata L., Cornus mas L. and Prunus spinosa L.) from southeast Serbia were determined by atomic absorption spectroscopy. Metal translocations from soil to fruit were calculated as well as their oral intake and health risk indices. Positive correlations were found among metal concentrations in soil, leaves and fruit.      

Biosorption of reactive dye from aqueous media using Saccharomyces cerevisiae biomass. Equilibrium and kinetic study

The biosorption Brilliant Red HE-3B reactive dye by nonliving biomass, Saccharomyces cerevisiae, in batch procedure was investigated. Equilibrium experimental data were analyzed using Freundlich, Langmuir and Dubinin — Radushkevich isotherm models and obtained capacity about 104.167 mg g^?1 at 20°C. The batch biosorption process followed the pseudo-second order kinetic model. The multi-linearity of the Weber-Morris plot suggests the presence of two main steps influencing the biosorption process: the intraparticle diffusion (pore diffusion), and the external mass transfer (film diffusion). The results obtained in batch experiments revealed that the biosorption of reactive dye by biomass is an endothermic physical-chemical process occurring mainly by electrostatic interaction between the positive charged surface of the biomass and the anionic dye molecules. The biosorption mechanism was confirmed by FT-IR spectroscopy and microscopy analysis      

Extractants selection for hyphenated electrothermal atomic absorption method

The theoretical approach for extractants selection during hyphenated atomic absorption determination of highly volatile metals (Pb, Cd), hydride- (Sb, Bi) and carbide-forming (Cr) metals using thermodynamic modelling was proposed. The calculated parameter — maximum pyrolysis temperature — can be used for selection of the extractants and chemical modifiers. Using this approach the antimony extract with Brilliant green was modified for which the 1.8-fold sensitivity and 2.6-fold repeatability decreasing while extract sampling in graphite furnace was observed. A chemical modifier — mixture of hydrazine nitrate with the palladium(II) complex with Xylenol orange — was theoretically selected and experimentally tested, which allowed to enhance the maximum pyrolysis temperature on 200°C, to eliminate extract matrix influence. Using this modifier two-fold increasing in sensitivity and 3-fold decreasing in relative standard deviation was achieved while extraction atomic absorption determination.      

The effect of increase in concentration of Na(I) ions on biosorption of Cr(III) ions by Enteromorpha prolifera and Spirulina sp

In this study, the effect of the increase in the initial concentration of Na(I) ions in the solution during biosorption of Cr(III) ions by two edible algae: marine macroalga — Enteromorpha prolifera and microalga — Spirulina sp. was investigated. During biosorption, essential elements are exchanged with alkali and alkaline earth metal ions (e.g. Na(I) ions), which are naturally bound with the biomass. The goal of this study was to investigate the effect of the increase in concentration of Na(I) ions on biosorption performance. The equilibrium of the process is described by Langmuir equation. It was found that with the increase in the initial concentration of NaCl (from 132 to 7331 mg L^?1), there was a lower biosorption capacity of Enteromorpha prolifera (from 85.8 to 51.0 mg g^?1) and Spirulina sp. (74.2 to 20.7 mg g^?1) towards Cr(III) ions. It was also possible to determine the number of times the solution used in the biosorption process can be recycled and yet mantain high biosorption capacity. The determined numbers were: 16 for Enteromorpha prolifera and 19 for Spirulina sp.      

Lead and cadmium atomic absorption determination in solid carbonized food samples using flame-furnace atomizer

Direct atomic absorption solid sampling analysis using flame-furnace atomizer enables a significant decrease in the analysis duration, to avoid sample pollution and to exclude toxic reagents. The selection of the chemical modifiers decreasing the detection limit and improving the results repeatability is based on the analyte’s free atoms formation mechanism. The developed kinetic approach has allowed to determine pre-exponential factors k₀ and apparent activation energies E_a of atomization processes for Pb(II) and Cd(II) compounds and to propose effective chemical modifiers sodium N,N-diethyldithiocarbamate and urea for food samples. The express and precision technique for lead and cadmium determination in food, using proposed chemical modifiers and carbonization techniques was developed.      

Square wave anodic stripping voltammetry determination of eco-toxic metals in samples of biological and environmental importance

Square wave anodic stripping voltammetry was used in simultaneous determinations of eco-toxic metals (Pb, Cd, Cu and Zn) on bismuth film electrodes. The electrodes were prepared in situ on a glassy-carbon electrode (GCE) from 0.1 M acetate buffer (pH 4.5) containing 200 μg L^?1 of bismuth (III), as well ex situ on electrochemically oxidized graphitized polyacrylonitrile carbon fibres from 200 mg L^?1 Bi(NO₃)₃ in 1% HNO₃ (aqueous) solution. Preparation of a Bi-modified carbon fibre electrode (CFE) was by cation exchange of Bi⁺³ ions for H⁺ of the acidic surface groups of the electro-oxidized carbon fibres, followed by electrochemical reduction to Bi⁰. For the Bi-GCE the linear range was 20–280 μg L^?1 for zinc, 10–100 μg L^?1 for lead, 10–80 μg L^?1 for copper, and 5–50 μg L^?1 for cadmium. For the Bi-CFE it was 20–160 μg L^?1 for zinc, 10–100 μg L^?1 for lead, 10–100 μg L^?1 for copper, and 2–120 μg L^?1 for cadmium. For both kinds of bismuth modified carbon electrodes, low limits of detection and satisfactory precision were achieved. The method was successfully applied to certified reference materials of biological (bovine liver) and environmental (mussel tissue) importance.      

Inactivation of cholinesterases by silver and gold ions in vitro

The main goal of the present study was to investigate the effects of silver and gold ions on cholinesterases (ChEs) activity due to increasing application of these metals in a wide variety of nanomaterials. A chromogenic assay using the substrate o-nitrophenyl acetate/butyrate made it possible to conclude unmistakably that both metals inhibit ChEs. Addition of bovine serum albumin (BSA) indicates that binding of metal ions to albumin could serve to scavenge metals and consequently reduce their amount for reaction with ChEs. The effects of metal ions on ChE should be taken into consideration when using this enzyme as an environmental biomarker.      

Polymer conjugates with potential biological activity based on new derivatives of 2-mercaptobenzoxazole-synthesis and characterization

New potentially biologically active compounds derived from 2-mercapto-benzoxazole were synthesized and coupled on polymeric support of poly (maleic anhydride-alt-vinyl acetate) for the preparation of polymer-drug conjugates with controlled drug release. All compounds were characterized by elemental and spectroscopy (FT-IR, ¹H-NMR) analysis. The toxicological tests recommend the products for further laboratory screening.      

Salutaridine and its derivatives as thebaine-equivalents in the synthesis of aporphines

Here we report the transformation of tetracyclic morphinan salutaridine (1) into 2,3,10,11-tetrasubstituted (R)-aporphines. This method serves as another chemical proof of the previously verified biosynthetic connection with pentacyclic morphinan-6,8-diene-type thebaine. In the presence of nucleophiles, this procedure could lead to pharmacologically interesting new tetrasubstituted aporphinoids. The enantioselective synthesis of 7S-salutaridinol (2) has been also achieved in order to investigate the acid-catalyzed reactions of this natural morphinan.      

Determination of lead in solution by solid phase extraction, elution, and spectrophotometric detection using 4-(2-pyridylazo)-resorcinol

Lead (+2) was selectively adsorbed on a solid phase extraction (SPE) gel (molecular recognition technology, MRT), quantitatively extracted, and spectrophotometrically determined as the Pb(II)-PAR (4-(2-pyridylazo)-resorcinol) complex. The linear range was 0.01 to 0.75 mg L^?1 and the detection limit was 6.4 µg L^?1. The MRT-SPE allows selective Pb(II) extraction from complex ion-rich matrices, which is difficult with other techniques. Interference from common matrix ions such as Fe²⁺, Ni²⁺, Cu²⁺ or Co²⁺ is minimized.      

Aerobic oxidation of cumene catalysed by 4-alkyloxycarbonyl-N-hydroxyphthalimide

4-Hexyloxycarbonyl-, 4-dodecyloxycarbonyl- and 4-hexadecyloxycarbonyl-N-hydroxyphthalimides were synthesised using trimellitic anhydride chloride as the starting material. The obtained lipophilic derivatives of N-hydroxyphthalimide were applied as catalysts of the cumene oxidation reaction with oxygen performed in polar acetonitrile, in non-polar tert-butylbenzene and in the absence of a solvent. The courses of reactions catalysed by N-hydroxyphthalimide and its derivatives were compared.      

Agglomeration of ZnS nanoparticles without capping additives at different temperatures

ZnS nanoparticles were precipitated in diluted aqueous solutions of zinc and sulphide ions without capping additives at a temperature interval of 0.5–20°C. ZnS nanoparticles were arranged in large flocs that were disaggregated into smaller agglomerates with hydrodynamic sizes of 70–150 nm depending on temperature. A linear relationship between hydrodynamic radius (R _a ) and temperature (T) was theoretically derived as R _a =652 - 2.11 T. The radii of 1.9–2.2 nm of individual ZnS nanoparticles were calculated on the basis of gap energies estimated from their UV absorption spectra. Low zeta potentials of these dispersions of ?5.0 mV to ?6.3 mV did not depend on temperature. Interactions between individual ZnS nanoparticles were modelled in the Material Studio environment. Water molecules were found to stabilize ZnS nanoparticles via electrostatic interactions.      

Extraction properties of β-aminophosphine oxides towards lanthanides and alkaline earth metals

The investigation of the extraction properties of a series of polyoligodentate β-aminophosphine oxides 1–8 bearing from one to six phosphine oxide groups in a molecule towards Ln(III) and alkaline earth metals ions from neutral media has revealed that, using common diluents, the extraction efficiency increases with an increase of a number of P=O functions in a ligand. The addition of ionic liquid, namely 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([bmim][NTf₂]), significantly increasing the extraction efficiency and application of IL concentration of 0.05 M (in 1,2-dichloroethane) providing the maximum recovery of metal ions with Lu/La separation factor reaching up to 91. Hexapodal tris[bis(2-diphenylphosphorylethyl)aminoethyl]amine 8 demonstrates the highest extraction under all conditions applied and the separation factor for U and Eu of this compound exceeded 10³.      

Comparative study of layered tetravalent metal phosphates containing various first-row divalent metals. Synthesis, crystalline structure

The transition metal forms of α-zirconium-. titanium-, and hafnium phosphates were prepared by ion exchange method. Their structure was investigated by X-ray powder diffraction (XRPD) method. It was found that the transition metal containing phosphates have the same layered structure as the pristine tetravalent metal phosphates, except for the increase of interlayer distance from 7.6 Å to ～9.5 Å. As a result of the incorporation of transition metals in the layers, the c-axis is increased from ～15 Å to ～20 Å (in the case of titanium phosphate to ～25 Å). All other parameters (a, b and β °) are practically unchanged.      

Supramolecular complexes of podand ligands with xenon

Formation of stable complexes between xenon and podand polyoxyethylene ligands was ascertained. The complexation process was studied by ¹²⁹Xe NMR titration, NMR diffusiometry and heteronuclear NOE measurements. The ligands studied form a 1:1 complexes with Xe(0). Their stability constants depend on the ligand structure, i.e., polyoxyethylene chain length, number of complexating polyether units and the topology of the anchoring centre.      

Stability prediction of Cu2+, Ni2+ and Zn2+ N-salicylidene-aminoacidato complexes by models based on connectivity index 3 χ v

This paper presents models for the estimation of stability constants (K ₁ and β ₂) of nickel(II), copper(II) and zinc(II) mono- and bis-complexes with 5 Schiff bases (salicylideneglycine, salicylidenealanine, salicylideneserine, salicylidenephenylalanine, and salicylidenetyrosine). The models were based on the molecular-graph theory and valence molecular connectivity index of the 3^rd order, ³χ ^v , derived from it. Univariate linear models were developed for each metal separately, while in the common models for two and three metals, the indicator variable, In, was introduced. The standard error of models for the log K ₁ constant was less than 0.12, while for log β ₂ models, the S.E. did not exceed 0.14.      

Synthesis and antiproliferative activity in vitro of new 2-aminobenzimidazole derivatives. Reaction of 2-arylideneaminobenzimidazole with selected nitriles containing active methylene group

A series of pyrimido[1,2-a]benzimidazole and α-cyanocinnamic acid derivatives have been synthesized in the reactions of Schiff bases 2–7 with selected nitriles containing an active methylene group: malononitrile 8–12, cyanoacetamide 13–16, benzyl cyanide 17–21, benzoylacetonitrile 22–24, cyanoacetate methyl ester 25–28 and benzylacetamide 29. The structures 8–29 were confirmed by the results of elementary analysis and their IR, ¹H-, ¹³C-NMR and MS spectra. The products 8–29 of various chemical structure pyrimido[1,2-a] benzimidazole 8–12, 14–16, 17–21, 23–24, 26 and α-cyanocinnamic acid derivatives 13, 22, 25, 27, 28 were obtained, which are of interest for biological studies or which can be substrates for further synthesis. The selected compounds 10, 13, 14, 17, 19, 21, 23–25 and 28 were screened for their antiproliferative activity in vitro against neoplastic and normal cell lines. The most active two compounds were: 2-(o-bromophenylene)-3-cyano-4-phenyl-1,2-dihydropyrimido[1,2-a]benzimidazole (24) and 3-cyano-4-phenyl-2-(2,4-dimethoxyphenyl)-1,2-dihydropyrimido[1,2-a]benzimidazole (23). However, similarly like cisplatin used as the control, they showed no selectivity towards cancer cells, by inhibiting proliferation of normal mouse fibroblasts in similar manner.      

Synthesis of 1-(pyrrolidin-2-ylmethyl)-1H-azoles and their piperidine-derived homologues

A convenient preparation of 1-(pyrrolidin-2-yl)-1H-pyrazoles, -imidazoles, and -1H-1,2,4-triazoles, 1-(piperidin-2-yl)-1H-pyrazoles and -1H-1,2,4-triazoles, and 1-(piperidin-3-yl)-1H-1,2,4-triazoles by alkylation of azoles (viz. pyrazoles, imidazoles, and triazoles) with N-Cbz-prolinol mesylate or its analogues and subsequent deprotection is reported. The two-step method allows for synthesis of the title compounds in 16–65% yields. The utility of the procedure has been demonstrated by multigram preparation of a 15-member building block mini-library for the lead-oriented synthesis of compound libraries. These building blocks perfectly fit the definition of low-molecular-weight hydrophilic three-dimensional templates, which leave much room for the lead-oriented synthesis of the compound libraries.