Open Access Published by De Gruyter Open Access

Volume 10 Issue 4

August 2012

Issue of Open Chemistry

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Contents
Journal Overview

Open Access May 29, 2012

Preconcentration procedures for the determination of chromium using atomic spectrometric techniques: A review

Xiaowei Zhao, Naizhong Song, Weihong Zhou, Qiong Jia

Page range: 927-937

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Abstract

Chromium is one of the regulated toxic metals in the environment. Naturally, this element exists mainly in two oxidation: Cr(III) and Cr(VI). In general, Cr(VI) is more toxic than Cr(III). Cr(VI) affects human physiology, accumulates in the food chain and causes severe health problems ranging from simple skin irritation to lung carcinoma. Hence, the determination of chromium traces as well as its speciation in environmental samples is a very important task. In recent years, several preconcentration methods such as coprecipitation, liquid-liquid extraction, dispersive liquid-liquid microextraction, cloud point extraction, and solid phase extraction have been developed and widely used. The aim of this study is to review the recent literature (mainly last 5 years) on the preconcentration technologies those have been used in chromium removal before the determination step by atomic spectrometric techniques. Their advantages and limitations in application are also evaluated.

Open Access May 29, 2012

Analytical sonochemistry; developments, applications, and hyphenations of ultrasound in sample preparation and analytical techniques

Shahram Seidi, Yadollah Yamini

Page range: 938-976

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Abstract

Ultrasonic assistance is one of the great successes of modern analytical chemistry, which uses this energy for a variety of purposes in relation to sample preparation and development of methods for the analysis of numerous contaminants including organic and inorganic compounds. This review will attempt to provide an overview of more recent applications of ultrasound in different environmental and biological samples such as food, soil and water as well as a brief description of the theoretical understanding of this method. Also, the possibility of coupling ultrasound with other analytical techniques will be discussed.

Open Access May 29, 2012

Electrode mechanism and voltammetric determination of selected guanidino compounds

Sławomira Skrzypek

Page range: 977-988

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Abstract

The present review describes the recent results on the electrochemical activity of bio-guanidino compounds, such as famotidine, metformin, acyclovir, ganciclovir, zanamivir, moroxydine as well as guanidino compounds, such as S-[(2-guanidino-thiazol-4-yl)methyl]isothiourea hydrochloride, 2-guanidino-1,3-thiazole, 2-guanidinobenzimidazole. The focus is on analyzing the electrode mechanism of the guanidino compounds at the hanging mercury drop electrode and at the silver amalgam film electrode, as well as on the character of the square wave (SW) voltammetric signals. It has been stated, that the compounds can act as electrocatalysts — they are protonated and adsorbed at the surface of the electrode, after which the protonated forms of the compounds are irreversibly reduced, yielding their initial form and hydrogen. The experimental adsorption data obtained by measuring the differential capacity of the double layer, the zero charge potential, and the surface tension at the zero charge potential have established the adsorption processes underlying their electrochemical activity. The analytical application of the obtained voltammetric signals in the determination of these compounds in biological samples is also presented. This review concentrates on our own results in the context of general developments in the field.

Open Access May 29, 2012

TiO2-assisted photodegradation of pharmaceuticals — a review

Alfred Tong, Rhiannon Braund, David Warren, Barrie Peake

Page range: 989-1027

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Abstract

Pharmaceutical compounds have been detected in the environment and potentially arise from the discharge of excreted and improperly disposed medication from sewage treatment facilities. In order to minimize environmental exposure of pharmaceutical residues, a potential technique to remove pharmaceuticals from water is the use of an advanced oxidation process (AOP) involving titanium dioxide (TiO2) photocatalysis. To evaluate the extent UV/TiO2 processes have been studied for pharmaceutical degradation, a literature search using the keywords ‘titanium dioxide’, ‘photocatalysis’, ‘advanced oxidation processes’, ‘pharmaceuticals’ and ‘degradation’ were used in the ISI Web of Knowledge TM, Scopus TM and ScienceDirect TM databases up to and including articles published on 23 November 2011. The degradation rates of pharmaceuticals under UV/TiO2 treatment were dependent on type and amount of TiO2 loading, pharmaceutical concentration, the presence of electron acceptors and pH. Complete mineralization under particular experimental conditions were reported for some pharmaceuticals; however, some experiments reported evolution of toxic intermediates during the photocatalytic process. It is concluded that the UV/TiO2 system is potentially a feasible wastewater treatment process, but careful consideration of the treatment time, the loading and the type of TiO2 (doped vs. undoped) used for a particular pharmaceutical is necessary for a successful application (198 words).

Open Access May 29, 2012

Molecular dynamics simulation study of the diamond D5 substructures

Anahita Kyani, Mircea Diudea

Page range: 1028-1033

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Abstract

Diamond D5 is the name proposed by Diudea for hyper-diamonds having their rings mostly pentagonal. Within D5, in crystallographic terms: the mtn structure, known in clathrates of type II, several substructures can be defined. In the present work, the structural stability of such intermediates/fragments appearing in the construction/destruction of D5 net was investigated using molecular dynamics simulation. Calculations were performed using an empirical many-body potential energy function for hydrocarbons. It has been found that, at normal temperature, the hexagonal hyper-rings are more stable while at higher temperature, the pentagonal ones are relatively more resistant against heat treatment.

Open Access May 29, 2012

Synthesis and biological activity of novel heavy metal complexes of 5-amino-1, 10-phenanthroline and 1,10-phenanthroline

Nikolay Kaloyanov, Mihail Neykov, Diana Wesselinova, Georgi Dimitrov

Page range: 1034-1041

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Abstract

Novel heavy metal complexes: Sr(5-NH2-phen)4(NO3)(OH)(H2O)2 (1) (synthesized via a static self-assembly process) and Sn(phen)(NO3)(OH)(H2O) (2), Sn(5-NH2-phen)(OH)(Cl)(H2O) (3), Pb(5-NH2-phen)(NO3)2(H2O) (4) (obtained via metal competitive reactions under mild conditions) were reported. The coordination compounds were characterized by elemental analysis, FTIR-spectroscopy and FAB-mass spectrometry. Their cytotoxicity was measured by MTS-test towards human tumour (MDA-MB-231, HT-29, HeLa, HepG2) and non-tumour diploid (Lep-3) cell lines. The most pronounced cytotoxic effect on all cancer lines showed 1 and 4 at their high concentrations as well as 1 at its lower ones (≤ 4×10−2 mg). Therefore, strontium complex of 5-amino-o-phenanthroline (1) exhibited the widest antitumour spectrum activity, having no toxicity to non-tumour cells at quantities ≤ 4×10−2 mg. The computed EC50 values of 1–4 against MDA-MB-231, HT-29, HeLa, HepG2 varied from 1.40×10−3 to 6.31×10−6 M. Towards Lep-3 substances 2–4 showed IC50 7.52×10−4 − 0.44 M. Substance 1 possess EC50=1.26×10−7 M to the non-tumour cells.

Open Access May 29, 2012

CORAL: the prediction of biodegradation of organic compounds with optimal SMILES-based descriptors

Andrey Toropov, Alla Toropova, Anna Lombardo, Alessandra Roncaglioni, Nicoletta Brita, Giovanni Stella, Emilio Benfenati

Page range: 1042-1048

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Abstract

CORAL software (http:/www.insilico.eu/coral) has been used to build up quantitative structure-biodegradation relationships (QSPR). The normalized degradation percentage has been used as the measure of biodegradation (for diverse organic compounds, n=445). Six random splits into sub-training, calibration, and test sets were examined. For each split the QSPR one-variable linear regression model based on the SMILES-based optimal descriptors has been built up. The average values of numbers of compounds and the correlation coefficients (r2) between experimental and calculated biodegradability values of these six models for the test sets are n=88.2±11.7 and r2=0.728±0.05. These six models were further tested against a set of chemicals (n=285) for which only categorical values (biodegradable or not) were available. Thus we also evaluated the use of the model as a classifier. The average values of the sensitivity, specificity, and accuracy were 0.811±0.019, 0.795±0.024, and 0.803±0.008, respectively.

Open Access May 29, 2012

Removal of ammonia emissions from waste air in a biotrickling filter: pilot-scale demonstration in real conditions

Luboš Zápotocký, Marek Šváb

Page range: 1049-1058

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Abstract

This study was aimed at testing the possibility of using a biotrickling filter for the treatment of waste air resulting from animal farming. For this purpose, a laboratory and pilot biotrickling filter with a moving bed were constructed. In the first case, the removal of ammonia emissions from waste air, by means of ammonia nitrogen utilization by present micro-organisms under laboratory conditions, was tested. The mass load of the biotrickling filter was gradually increased by slowly increasing the ammonia concentration. In the second case, the pilot biotrickling filter with a moving bed was installed inside a pig farm and it was tested under real operation conditions. In the first case, the highest value of the laboratory biotrickling filter’s elimination capacity was 6.2 gNH3 m−3 of filling h−1. The elimination capacity of the pilot filter was 1.6 gNH3 m−3 of filling h−1. The source of carbon for the present micro-organisms was a 1% sucrose solution, which simulated waste water with high content of CODCR. [

Open Access May 29, 2012

Preparation of a series of N-alkyl-3-boronopyridinium halides and study of their stability in the presence of hydrogen peroxide

Yevgen Karpichev, Hubert Matondo, Illia Kapitanov, Oleksandr Savsunenko, Marc Vedrenne, Verena Poinsot, Isabelle Rico-Lattes, Armand Lattes

Page range: 1059-1065

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Abstract

A simple and efficient protocol for the preparation of a series of N-alkyl-3-boronopyridinium salts is described which requires exposure of 3-pyridineboronic acid neopentylglycol ester and corresponding alkyle halide to microwave irradiation followed by boronic ester hydrolysis. The technique employed drastically reduces the reaction time and prevents thermal degradation and the formation of side products. Water solutions of the obtained boronopyridinium salts are shown to be stable at room temperature in wide pH range as well as in the presence of hydrogen peroxide at pH 10.0 for 72 h.

Open Access May 29, 2012

Chiral enantiopure bis(thio)ureas derived from TADDOL and their carboxylate complexation capacity

Dragos Gherase, Christian Roussel

Page range: 1066-1072

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Abstract

New chiral enantiopure ureas and thioureas with (R,R)-TADDOL backbone were synthesized. Bis-(thio)ureas with C2 symmetry were obtained from TADDOL iso(thio)cyanates and bifunctional amino-(thio)ureas from TADDAMINE, respectively. These were tested for carboxylate recognition capacity and the association constant was determined for the most stable complex.

Open Access May 29, 2012

Impact of un-polymerized acrylamide monomer residues onto protein identification by MALDI TOF MS

Ivan Talian, Veronika Kováčová, Marián Petrovič, Ján Sabo

Page range: 1073-1078

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Abstract

Polyacrylamide gel electrophoresis is a powerful tool for protein mixture separation frequently used in proteomic studies. This article describes the problems which can arise during the identification process of separated proteins by matrix assisted laser desorption/ionization mass spectrometry. Presence of residual acrylamide monomers in the peptide samples leads to a significant peptide signal suppression. In the case of protein prohibitin, isolated from the MCF 7 breast cancer cell line, the peptide signal suppression was observed in 50% of all detected peptides.

Open Access May 29, 2012

New iron-cobalt clusters with silicon-containing dicarboxylic acids

Maria Cazacu, Angelica Vlad, Constantin Turta, Gabriela Lisa

Page range: 1079-1086

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Abstract

For the first time, silicon-containing dicarboxylic acids were used to prepare two new heterotrinuclear carboxylates of the composition [Fe2IIICoIIO(Bcpdps)3(H2O)3], I, where H2Bcpdps ≡ HOOC-C6H4-Si(C6H5)2-C6H4COOH, and [Fe2IIICoIIO(Ipds)3(H2O)3], II, where H2Ipds ≡ [HOOC-C6H3(CO)2N-(CH2)3-(CH3)2Si]2O. The precursor for these two complexes was trinuclear µ3-oxo-hexaacetate triaqua diiron(III)cobalt(II) cluster, {Fe 2 CoO}, in which the acetate anions were subsequently substituted by silicon-containing dianions. The resulting products were characterized by elemental analysis, thermogravimetry, Fourier Transform Infrared (FTIR), Energy-Dispersive X-ray Fluorescence (EDXRF), and Mossbauer spectroscopies (MS). The investigation by MS revealed the presence of the iron(3+) ions in high spin state and having the close environment. Thermogravimetric analysis results indicated an improving in the thermal stability by replacing acetate anions with silicon-containing carboxyl ligands. This widens the temperature range in which such compounds can be used in practical applications.

Open Access May 29, 2012

Unusual reaction of 3,4-bis(3-nitrofurazan-4-yl)furoxan with ammonia, primary amines and hydrazine

Alexander Astrat’ev, Dmitry Dashko, Andrei Stepanov

Page range: 1087-1094

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Abstract

The nucleophilic displacement of two nitro groups in 3,4-bis(3-nitrofurazan-4-yl)furoxan with ammonia, primary aliphatic amines and hydrazine leads to formation of a novel heterocyclic system, 7H-tris[1,2,5]oxadiazolo[3,4-b:3′,4′-d:3″,4″-f]azepine. The reaction of compound 1 with secondary aliphatic amines proceeds in a typical way for nitrofurazans when the nitro-group in the starting compound is substituted by RR’N-group.

Open Access May 29, 2012

Spectroscopic and magnetic properties of Cu(II) complexes with selected biologically important ligands

Renata Świsłocka, Monika Kalinowska, Wiesława Ferenc, Jan Sarzyński, Włodzimierz Lewandowski

Page range: 1095-1105

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Abstract

The aim of this work was to study the spectroscopic and magnetic properties of copper(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates. The complexes were synthesized and their compositions were evaluated by elementary analysis. The infrared and Raman spectra for Cu(II) aminobenzoates, methoxybenzoates and nitrobenzoates were recorded and assigned. The obtained data were compared with those previously published for aminobenzoic, methoxybenzoic and nitrobenzoic acids and their sodium salts. The structures of Cu(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates as well as the change in the electronic charges distribution caused by Cu(II) complex formation were discussed.

Open Access May 29, 2012

Morphological, structural and optical properties of MoO2 films electrodeposited on SnO2∣glass plate

Nijole Dukstiene, Dovile Sinkeviciute, Asta Guobiene

Page range: 1106-1118

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Abstract

MoO2 films were prepared by electrodeposition under potential controlled conditions from an aqueous alkaline solution of sodium molybdate. Optical microscopy showed that films of different morphology were deposited. The surface roughness and grain size were determined by atomic force microscopy. The characterization of as-deposited films by X-ray diffraction analysis revealed their amorphous nature. The optical constants of films were derived from transmittance spectra recorded in the 310–1100 nm wavelength range. All films were highly absorptive and showed a direct band to band transition. From the absorption edge data, the values of the optical band gap E g and the Urbach energy E U were determined based on Tauc’s model. The influence of film thickness on the extinction coefficient k, refractive index n, absorption coefficient a and the band gap energy E g was studied.

Open Access May 29, 2012

New serinolic amino-s-triazines by chemoselective amination of cyanuric chloride and their (pro)diastereomerism in restricted rotational phenomena

Oana Moldovan, Pedro Lameiras, Eric Henon, Flavia Popa, Agathe Martinez, Dominique Harakat, Carmen Sacalis, Yvan Ramondenc, Mircea Darabantu

Page range: 1119-1136

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Abstract

The highly chemoselective preparation of new elaborated N-unsymmetrically substituted chlorodiamino-s-triazines and melamines, seen as building-blocks for iterative synthesis, is reported. It consisted of amination of cyanuric chloride with commercial C-2-substituted 2-aminopropane-1,3-diols (“serinols”), playing the role as “open-chain” unit and enantiopure (1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diols (“p-nitrophenylserinols”) based amino-1,3-dioxanes (“closed-chain” unit). Issued from the restricted rotation about C(s-triazine)-N(exocyclic) partial double bonds, seen as axes of (pro)diastereomerism, a global four-component rotational equilibrium involving the title compounds is discussed based on DFT computation and (VT) NMR data. Depending on π-deficiency of the s-triazine core, an (un)synchronised deblocking of the generated rotational diastereomers was observed. They are discussed as influence of intra-vs. intermolecular NH...OH (dynamic) interactions occurring in the “open-chain” unit and the anancomeric, axial vs. equatorial, amino-anchorage of the “closed-chain” unit.

Open Access May 29, 2012

The photocatalytic degradation of 17α-ethynylestradiol by pure and carbon nanotubes modified TiO2 under UVC illumination

Radina Kralchevska, Maria Milanova, Mirjana Bistan, Albin Pintar, Dimitar Todorovsky

Page range: 1137-1148

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Abstract

Commercial product Degussa TiO2 P25, sol-gel produced TiO2 and TiO2 modified by carbon nanotubes addition (5% of the TiO2 mass) are tested as photocatalysts for the degradation of endocrine disrupting compound 17α-ethynylestradiol (1 µM aqueous solution). The molecular and crystal structure, phase composition, crystallite size, specific surface area, pore average diameter, their area and volume distribution, morphology, IR and UV/Vis spectra of the catalysts are characterized. HPLC is used for estrogen analysis. The sorption ability and photocatalytic activity (measured by degradation rate constant and percentage of the pollutant conversion) of the catalysts under UV (17 W, emission maximum at 254 nm) irradiation is determined. Full destruction of the pollutant is reached after 30 min irradiation in presence of Degussa P25. The performance of some of the catalysts is compared with literature data for their activity under 365 nm-illumination.

Open Access May 29, 2012

Instance-based regression with missing data applied to a photocatalytic oxidation process

Florin Leon, Ciprian Piuleac, Silvia Curteanu, Ioannis Poulios

Page range: 1149-1156

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Abstract

In this paper, a modified nearest-neighbor regression method (kNN) is proposed to model a process with incomplete information of the measurements. This technique is based on the variation of the coefficients used to weight the distances of the instances. The case study selected for testing this algorithm was the photocatalytic degradation of Reactive Red 184 (RR184), a dye belonging to the group of azo compounds, which is widely used in manufacturing paint paper, leather and fabrics. The process is conducted with TiO2 as catalyst (an inexpensive semiconductor material, completely inert chemically and biologically), in the presence of H2O2 (with the role of increasing the rate of photo-oxidation), at different pH values. The final concentration of RR184 is predicted accurately with the modified kNN regression method developed in this article. A comparison with other machine learning methods (sequential minimal optimization regression, decision table, reduced error pruning tree, M5 pruned model tree) proves the superiority and efficiency of the proposed algorithm, not only for its results, but for its simplicity and flexibility in manipulating incomplete experimental data.

Open Access May 29, 2012

Towards understanding of protein adsorption behavior on plasma polymerized pyrrole film

Zhihong Zhang, Guijuan Li, Fufeng Yan, Xianjun Zheng, Xili Li

Page range: 1157-1164

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Abstract

Plasma polymerized pyrrole-like (PPpy) films exhibit good environmental stability and offer high reactivity with biomolecules. The present paper follows on from previous work on PPpy films applied as DNA immobilization/hybridization and describes the adsorption kinetics of bovine serum albumin (BSA) on PPpy films. Atom force microscopy was used to detect the surface roughness of PPpy surfaces obtained at different input powers or for different polymerization time, including the surface roughness before and after BSA adsorption. The influence of experimental conditions (i.e., the plasma input power, the polymerization time, the concentration of BSA, and the pH values of buffer solutions) on protein adsorption was investigated in situ by Surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the differently dynamic adsorption behavior of BSA on PPpy films under various experimental conditions. The adsorption constant, K a , was deduced from Langmuir isotherm equations, which were simulated using experimental data collected by SPR and electrochemical impedance spectroscopy (EIS). Analysis of the combination data of SPR and EIS indicates that PPpy films under various conditions show completely different adsorption behaviors and could be applied as biomaterials for electrochemical protein sensing or as protein-resistant.

Open Access May 29, 2012

Synthesis, crystal structure, spectroscopic and thermal investigations of neodymium(III) biphenyl-4,4′-dicarboxylate framework

Renata Łyszczek, Liliana Mazur

Page range: 1165-1174

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Abstract

The three-dimensional complex {[Nd(bpdc)1.5(DMF)]·1.4DMF}n (DMF=N,N′-dimethylformamide, bpdc=biphenyl-4,4′-dicarboxylate) was synthesized using the solvothermal method. The crystal structure of the neodymium(III) complex has been determined by single-crystal X-ray diffraction method at 100(2) K. The polymeric structure consists of neodymium polyhedra bridged by bpdc ligands. Eight-coordinated Nd(III) atoms are surrounded by seven oxygen atoms from six bpdc moieties and one oxygen atom from the DMF molecule. The 3D structure of the complex contains two types of channels occupied by DMF molecules. Thermal analysis revealed that DMF molecules are lost in a stepwise manner. The infrared spectrum confirmed full deprotonation of acid and presence of DMF molecules in the structure.

Open Access May 29, 2012

Mercury determination and speciation analysis in surface waters

Elisaveta Mladenova, Ivanka Dakova, Dimiter Tsalev, Irina Karadjova

Page range: 1175-1182

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Abstract

A sorbent L-cysteine grafted silica gel has been evaluated for separation and enrichment of dissolved inorganic i-Hg(II) and methylmercury CH3Hg(I) from surface waters at sub-µg L−1 concentrations. Chemical parameters for mercury species enrichment and separation have been optimized. Analytical schemes for the determination of Hg species, using selective column solid phase extraction (SPE) with continuous flow chemical vapor generation atomic absorption spectrometry (CF-CVG-AAS) or inductively coupled plasma-mass spectrometry (ICP-MS) were developed. Possibilities for on-site SPE enrichment were demonstrated as well. The limits of quantification were 1.5 and 5 ng L−1 for dissolved i-Hg(II) and CH3Hg(I) by CF-CVG-AAS and 1 and 2.5 ng L−1 by ICP-MS with relative standard deviations between 7–12% and 7–14%, respectively. The chemically modified SPE sorbent has demonstrated high regeneration ability, chemical and mechanical stability, acceptable capacity and good enrichment factors. Results for total dissolved mercury were in reasonable agreement with those from independent analyses by direct ICP-MS determinations for river waters and for estuarine water certified reference material.

Open Access May 29, 2012

The effect of anatase crystal morphology on the photocatalytic conversion of NO by TiO2-based nanomaterials

Marco Abreu, Edisson Morgado, Paula Jardim, Bojan Marinkovic

Page range: 1183-1198

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Abstract

Hydrogen titanate nanotubes (H-TTNT) were synthesized by the alkali hydrothermal method followed by proton exchange and then submitted either to thermal treatment or to acid hydrothermal reaction to generate TiO2-anatase nanocrystals of different morphologies. The samples were characterized by XRPD, TGA, sulfur analysis, N2 physisorption, UV-Vis spectroscopy and TEM. Their photocatalytic activities were determined by measuring the NO conversion in inert gas stream passed through the powder catalyst bed under UV radiation. Incomplete transformation into anatase resulted in nanomaterials with low activity due to coexistence with H-TTNT or TiO2-B precursors. Anatase specimens derived from H-TTNT aged in strong sulfuric acid media contained equidimensional nanoparticles, but retention of sulfate negatively affected their photocatalytic activity. Combining milder acidic pH with higher aging temperature, allowed synthesis of a sulfate free anatase with the same optical properties and specific surface area as the counterpart produced by calcination of H-TTNT at 550°C; however, the former exhibited truncated bi-pyramid nanocrystals and the other adopted the form of nanorods. This latter showed the highest photocatalytic activity for NO abatement, outperforming the benchmark photocatatyst TiO2-P25; this improved activity was tentatively ascribed to the maximization of high energy {001} facets in anatase nanorods formed during calcination of H-TTNT.

Open Access May 29, 2012

Trans influence of triphenylphosphines and pseudohalogens on Ni-S bonds: Synthesis, spectral and single crystal X-ray structural studies on NiS2PN and NiS2PC chromophores

Kuppukkannu Ramalingam, Raghavan Thiruneelakandan, Gabriele Bocelli, Lara Righi

Page range: 1199-1207

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Abstract

Trans influence of triphenylphosphines and pseudohalogens on Ni-S bonds of NiS2PN and NiS2PC chromophores has been investigated by synthesizing and characterizing them. The complexes show the characteristic thioureide IR band at ∼ 1530 cm−1. Electronic spectrum of the cyanide analogue shows a strong blue shift relative to others. X-ray structures of [Ni(pipdtc)(4-MP)(NCS)] (1), [Ni(pipdtc)(PPh3)(NCS)] (2) and [Ni(pipdtc)(PPh3)(CN)] (3) (pipdtc = piperidinecarbodithioate anion, 4-MP = tri(4-methylphenyl)phopshine) are reported. Ni-S bond distance trans to 4-MP(1) is longer than the distances in (2) and (3) and Ni-S bond distances trans to Ni-NCS/CN decrease as follows: (3) > (2) > (1). Particularly, 4-MP shows a highly significant trans influence than triphenylphosphine on Ni-S bond. Similarly, CN− exerts a marginally significant trans influence compared to NCS-. Thioureide C-N distances are relatively very short due to the drift of electron density towards the metal. The Ni-N-C angle (163.5(2)°) observed in (2) indicates deviation from linearity to a larger extent compared to that in (1) (176.3(3)°) due to the steric effect of the 4-methyl group. The reduction potentials (CV) for the mixed ligand complexes are much less compared to that of the parent NiS4 chromophore due to the π-acidic phosphines.

Open Access May 29, 2012

Supported H4SiW12O40 catalysts for α-pinene isomerization

József-Zsolt Szücs-Balázs, Maria Coroş, Adrian Woiczechowski-Pop, Gabriela Blăniƫă, Mircea Vlassa

Page range: 1208-1217

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Abstract

The heterogeneous isomerization of α-pinene was studied at 100, 130 and 160°C using 10% supported H4SiW12O40 (SiW) on SiO2, TiO2 and HZSM-5. The effect of the reaction temperature and the concentration of the catalyst over the conversion of α-pinene and the selectivity of camphene, limonene and terpinolene had been monitored. The recovery, reuse and leaching effect of the catalysts were studied. Simple, environmentally friendly and economic methods for the synthesis of camphene and limonene were developed and optimized.

Open Access May 29, 2012

Diironcarbonyl-coumarin complex: preparation, intramolecular electron transfer, and electro-generation of hydrogen

Charles Mebi, Joshua Trujillo, Anwar Bhuiyan

Page range: 1218-1222

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Abstract

A new organometallic complex coupling photoactive coumarin to a diironhexacarbonyl unit has been successfully prepared and its composition and electronic structure confirmed by elemental and spectroscopic analyses. Emission spectral analysis of the complex reveals photoinduced intramolecular electron transfer from coumarin to the iron-carbonyl moiety. The compound is electrochemically reduced at −1.24 V vs. Fc/Fc+. This reduction is irreversible, attesting to the instability of the complex. Electrochemical evolution of hydrogen in the presence of the complex has been studied and results are discussed.

Open Access May 29, 2012

Simulating pollutant transport over complex terrain: the hydrological component

Constantina Mita, Nicolaos Catsaros

Page range: 1223-1235

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Abstract

The accurate determination of surface water flow pathways is of primary importance when assessing the impact of pollutant transport and watershed physical characteristics on overland and channel water quality. The mathematical description of hydrological processes over natural watersheds, requires a detailed representation of the topography, on which the accurate determination of overland and channel flow trajectories often poses difficulties. The hydrological component of the DELTA code aims to provide valuable insight into this direction by using the semi-irregular triangulated (semi-TIN) topography model DELTA/HYDRO for establishing surface flow paths that can represent reliably the natural characteristics of a watershed, addressing several major physical hydrodynamic processes. The validity of the generated paths is tested via the integration of a conventional distributed hydrological model by routing excess rainfall over ground surface and through a channel network to the watershed outlet, for a series of storm episodes on a small, but relatively complex watershed. The encouraging results obtained demonstrate the promising application potential of the model, which can be additionally complemented with a pollutant transport component to address the interactions of soluble chemicals between soil surface and overland/channel flow, in the context of a fully integrated model.

Open Access May 29, 2012

Temperature effects on the adsorption of polyvinyl alcohol on silica

Małgorzata Wiśniewska

Page range: 1236-1244

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Abstract

The influence of temperature on the adsorption of polyvinyl alcohol (PVA) on a silica surface was studied from 15–35°C. The structure of the polymer adsorption layer was determined from spectrophotometric, viscosity and thermogravimetric measurements. The amount of PVA adsorbed, macromolecules’ conformation in solution, thickness of the polymer adsorption layer, and changes in the heating curve of SiO2 with adsorbed polymer were determined. Temperature influences the PVA chain conformation in solution and the structure of the polymer adsorption layer. A temperature rise causes relaxation of polymer coils which results in an increase in the linear dimensions of PVA chains in the solution, the creation of a thicker adsorption layer, and an increase in polymer adsorbed. Polymer adsorption on the silica surface also causes changes in the heating curve of these systems. The mass losses due to heating are smallest for the systems obtained at 15°C because the least polymer is adsorbed at this temperature.

Open Access May 29, 2012

Altered membrane amino acids composition in human colorectal cancer tissue

Barbara Szachowicz-Petelska, Stanisław Sulkowski, Zbigniew Figaszewski

Page range: 1245-1252

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Abstract

Cancer transformation is characterized by changes in cell metabolism, which can alter the structure and function of cell membrane components, including integral membrane proteins. Qualitative and quantitative estimations of integral membrane protein are necessary for studies aimed at understanding their modifications under pathological conditions. Herein, we used a high-performance liquid chromatography (HPLC)-based approach that involved selective hydrolysis of isolated tissue cell membrane proteins to peptides, resolution by chromatography and determination of the amino acid content (phenylalanine (Phe), tyrosine (Tyr), cysteine (Cys) and lysine (Lys)) in individual peptides. The results demonstrate decrease in peptide levels and their amino acids content in integral membrane proteins in human colorectal cancer tissue. Therefore, cancer transformation causes a decrease in the levels of integral membrane proteins, which may in turn lead to an increase in the levels of other charged molecules on the cell surface, such as phospholipids. It might lead to the reconstruction and functional rearrangement of the cell membrane, for example: the permeability, electric properties, fluidity etc.

Open Access May 29, 2012

The interaction of [Pd(N,N-dimethylaminopropylamine)(H2O)]2+ with dicarboxylic acids and inosine: Thermodynamic model for carboplatin drug

Mohamed Shehate, Mohamed Shoukry, Mona Ragab

Page range: 1253-1261

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Abstract

The Pd(DMPA)Cl2 complex, where DMPA = N,N-dimethylaminoproylamine, was synthesized and characterized. The stoichiometry and stability constants of the complexes formed between various dicarboxylic acids and [Pd(DMPA)(H2O)2]2+ were investigated. The effect of solvent dielectric constant, chloride ion concentration of the medium and temperature on the stability constant of the cyclobutanedicaroxylic acid (CBDCA) complex was investigated. The equilibrium constants for the displacement of coordinated CBDCA by inosine, taken as an example of DNA constituents, were calculated. The results are expected to contribute to the chemistry of antitumour agents.

Open Access May 29, 2012

Extraction-spectrophotometric investigations on two ternary ion-association complexes of gallium(III)

Kirila Stojnova, Kiril Gavazov, Galya Toncheva, Vanya Lekova, Atanas Dimitrov

Page range: 1262-1270

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Abstract

Complex formation and liquid-liquid extraction were studied in systems containing Ga(III), azoderivative of resorcinol {4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR)}, 2,3,5-triphenyltetrazolium chloride (TTC), water and chloroform. The optimum conditions w.r.t. pH, extraction time, concentration of ADR and concentration of TTC for the extraction of Ga(III) as an ion-associate complex were found.. The composition of the extracted complexes, (TT+)[Ga(PAR)2] (I), (TT+)[Ga(TAR)2] (II) or (TT+)2[Ga(OH)(TAR)2] (III), and the constants of association (β) between 2,3,5-triphenyltetrazolium cation (TT+) with corresponding anionic chelates were established by several methods. The constants of distribution (KD) and extraction (Kex) of the principal species I and III were determined as well. The apparent molar absorptivities of the chloroform extract at the optimum extraction-spectrophotometric conditions were ɛ′510=9.5×104 L mol−1 cm−1 (I) and ɛ′530=4.6×104 L mol−1 cm−1 (III). The validity of Beer’s law was checked and analytical characteristics that were calculated are reported herein.

Open Access May 29, 2012

Glassy carbon and boron doped glassy carbon electrodes for voltammetric determination of linuron herbicide in the selected samples

Jelena Đorđević, Ana Kalijadis, Ksenija Kumrić, Zoran Jovanović, Zoran Laušević, Tatjana Trtić-Petrović

Page range: 1271-1279

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Abstract

In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000°C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E p ) of linuron oxidation in 0.1 mol dm−3 H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm−3 H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005–0.1 µmol cm−3) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds.

Open Access May 29, 2012

A study of the antioxidative behavior of phenolic acids, in aqueous herb extracts, using a dsDNA biosensor

Elina Skeva, Stella Girousi

Page range: 1280-1289

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Abstract

Electrochemical DNA biosensors are promising tools for the fast, inexpensive and simple in vitro analysis for the determination of free radicals and antioxidants. High concentrations of antioxidants in such compounds as phenolic acids and plant extracts, act as free radical terminators which reduce the effect of the oxidative dam-age on DNA. The electrochemical behavior of three representative phenolic acids, caffeic acid, gallic acid and trolox were studied by cyclic voltammetry. Moreover, the determination of the above antioxidants under the optimized conditions (scan rate, deposition potential and time) using differential pulse voltammetry was also investigated. In vitro studies focused on their antioxidative effect were performed by adsorptive transfer stripping voltammetry and dsDNA biosensor. Using Fenton’s system, with FeSO4 and H2O2 was chosen as a strong oxidative system. This biosensor was applied as a screening antioxidant test in order to estimate the antioxidant capacity of aqueous herb extracts.

Open Access May 29, 2012

Adsorption of cystine at mercury/ aqueous solution of chlorate (VII) interface in solutions of different water activity

Agnieszka Nosal-Wiercińska

Page range: 1290-1300

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Open Access May 29, 2012

The dominant contribution on wet deposition of water-soluble main ions in the South-Eastern Adriatic region

Pavle Đurašković, Ivana Tošić, Miroslava Unkašević, Ljubiša Ignjatović, Dragana Đorđević

Page range: 1301-1309

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Abstract

The results of content of water-soluble ions measured in 604 samples of precipitation collected in South-Eastern Adriatic region during 6 years have been analyzed. The HYSPLIT model was used to study the air mass paths. Although the ion concentrations of investigated ions in precipitation of air masses from the continental parts of Europe were significant, the total wet deposition is dominated by precipitation coming over the Mediterranean Sea. The sea salt components are significantly correlated. The correlations between Ca2+ and Mg2+, Ca2+ and SO42− and Ca2+ and K+ indicate the main terrigeneous ions.

Open Access May 29, 2012

Voltammetric and amperometric determination of metoclopramide on boron-doped diamond film electrode

Hana Dejmkova, Candan Dag, Jiri Barek, Jiri Zima

Page range: 1310-1317

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Abstract

New methods for the determination of metoclopramide, antiemetic and gastroprokinetic pharmaceutical, were developed, using differential pulse voltammetry (DPV) and flow injection analysis (FIA) with amperometric detection on a boron-doped diamond film electrode. Electrode pretreatment necessary to ensure the stable results was investigated and it was found, that while DPV requires frequent electrode cleaning, FIA with a sufficiently high flow rate can maintain a stable signal with no signs of electrode passivation. The calculated quantification limits of the DPV and FIA with amperometric detection were 0.13 μmol L−1 and 0.015 mmol L−1, respectively. The applicability of the new methods was verified by the determination of metoclopramide in a pharmaceutical preparation. FIA with amperometic detection proved to be sensitive, accurate and, due to the resistance of the electrode to the passivation, also simple to handle.

Open Access May 29, 2012

The classification of solvents based on solvatochromic characteristics: the choice of optimal parameters for artificial neural networks

Yaroslava Pushkarova, Yuriy Kholin

Page range: 1318-1327

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Abstract

The Taft-Kamlet-Abboud hydrogen-bond acidity, hydrogen-bond basicity and polarity-polarizability are widely used as empirical characteristics of solvent-solute interactions. These solvatochromic parameters are determined from the absorption band positions of solvatochromic probes in the standard medium and in the medium under study. The practice of solvatochromic probing is growing rapidly, and the values of solvatochromic parameters are refined from time to time. As these values are rather close for many media, the classification of media based on these values can be tedious. This increases the choice of algorithms that can be employed in order to decrease the ambiguity of classification. The classification algorithms stable to small variations of solvatochromic parameters are of special interest. The artificial neural networks (ANN) proved to be a powerful tool for the supervised classification. The paper focuses on the search of optimal parameters of probabilistic, dynamic, Elman, feed-forward, and cascade ANN for the classification of solvent on the basis of their solvatochromic characteristics. Also, the influence of data variation on the stability of classification is examined. The dynamic and probabilistic neural networks have been found to be error-free and stable; they have significantly become such a common tool for supervised classification as linear discriminant analysis.

Open Access May 29, 2012

Prediction of properties of biodiesel-diesel blends using spectrofluorimetry and multivariate calibration

Marilena Meira, Cristina Quintella, Iuri Pepe, Pedro Costa Neto, Alessandra Santos Tanajura, Humbervânia Silva

Page range: 1328-1337

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Abstract

Regressions based on fluorescence spectroscopy were developed to provide relatively inexpensive and rapid measurements of the concentration, viscosity, and specific gravity of biodiesel-diesel blends. The methods involved obtaining a mathematical model from spectrofluorimetric data and data from a given property (concentration, dynamic viscosity, or specific gravity) using partial least squares (PLS) regression, which was then applied as a model for predicting properties of interest. The predicted concentrations, dynamic viscosities, and specific gravities of the biodiesel-diesel blends were compared with actual values and agreed reasonably well with the obtained results. The models showed high correlation between real and predicted values. The R-square values near 1 indicated excellent model accuracy for predicting concentrations, specific gravities, and dynamic viscosities of biodiesel-diesel blends. The residual distribution did not follow a trend with respect to the predicted variables, indicating an excellent fit to the data.

Open Access May 29, 2012

Thermo-responsiveness of polysiloxanes grafted with poly(dimethyl acrylamide) segments

Anca Rusu Hodorog, Constanta Ibanescu, Ioana Moleavin, Nicolae Hurduc

Page range: 1338-1348

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Abstract

Thermo-sensitive polymers are of outstanding importance due to their ability to undergo controlled major changes in their properties as a response to minor modifications in temperature. The syntheses of novel polymers by grafting polysiloxane containing chlorobenzyl groups in the side chain by the homopolymerization of N,N′-dimethyl acrylamide (DMA) or the copolymerization of DMA and methyl methacrylate (MMA) using SET-LRP technique are presented. The polymers were characterized by 1H-NMR, UV, and fluorescence spectroscopy, and DSC. The thermo-sensitivity and the lower critical solution temperature (LCST), as well as the aggregation phenomena during the phase transition are evidenced by dynamic light scattering (DLS) and rheology.

Open Access May 29, 2012

A promising absorbent of acrylic acid/poly(ethylene glycol) hydrogel prepared by glow-discharge electrolysis plasma

Quanfang Lu, Jie Yu, Jinzhang Gao, Wu Yang, Yan Li

Page range: 1349-1359

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Abstract

An acrylic acid/poly(ethylene glycol) (AAc/PEG) hydrogel was synthesized in aqueous solution by a simple one-step method using glow-discharge electrolysis plasma (GDEP) technique. The structure of AAc/PEG hydrogel was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Factors influencing the adsorption of heavy-metal ions such as solution pH, contact time, initial heavy-metal ion concentration were examined systematically by batch experiments. Results showed that both chemical complexation and ion exchange played an important role for heavy-metal ion adsorption onto AAc/PEG hydrogel. The adsorption isothermals followed the Langmuir isotherm and the adsorption kinetics fitted the pseudo-second-order model at 25°C with a pH 6. In addition, AAc/PEG hydrogel can be also regenerated and re-used.

Open Access May 29, 2012

Use of an immiscible diluent in ionic liquid / ion pair LC for the assay of an injectable analgesic

Toma Galaon, Medeea Radulescu, Victor David, Andrei Medvedovici

Page range: 1360-1368

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Abstract

Injectable solutions used in treatment of intense pain are based on combinations of active ingredients such as metamizole sodium (MTZ), pitofenone hydrochloride (PTF) and fenpiverine bromide (FPB). The simultaneous chromatographic assay of such combinations poses difficulties due to their structural variety, highly polar character, and wide concentration ranges (500 mg mL−1 for MTZ, 2 mg mL−1 for PTF and 0.02 mg mL−1 for FPB). Fast hydrolysis of MTZ on aqueous dilution causes additional problems due to impurity (MTC) formation. Sodium hexane sulphonate (10 mM) was used as ion pairing agent for PTF, FPB and MTC in a mobile phase consisting of 48/52 (v/v) methanol and aqueous 0.2% triethylamine at pH=3. The ionic liquid 1-butyl-1-methyl-pyrrolidinium tetrafluoroborate (10 mM) was used as mobile phase additive to preserve the MTZ peak symmetry. The minor active ingredient FPB was selectively extracted into 1-octanol by ion pair formation with picric acid. A 20 µL aliquot of the organic layer was directly injected into the column.

About this journal

Open Chemistry is a peer-reviewed open access journal that publishes original research, reviews, and communications in the fields of chemistry in an ongoing way. Our central goal is to provide a hub for researchers working across all subjects to present their discoveries, and to be a forum for the discussion of the important issues in the field.

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Open Chemistry aims to publish high quality research in the following areas:

Biological Chemistry/Biochemistry including bioanalytical chemistry, biochemistry and biological chemistry, biophysics and chemical physics in biology

Analytical Chemistry including electrochemistry, environmental chemistry, spectroscopy
Physical Chemistry including catalysis, chemical kinetics and reactivity, chemical physics, computational chemistry, chemometrics and QSAR, hydrogen technologies, hydrogen storage, nanochemistry, photochemistry, physical chemistry and physical organic chemistry, radiochemistry and nuclear chemistry, supramolecular chemistry, surface chemistry and colloids, theoretical chemistry, thermodynamics
Inorganic Chemistry including coordination chemistry, crystallography, materials and solid- state chemistry
Organic Chemistry including macromolecules and polymers, natural product chemistry, organic chemistry, organometallic chemistry, phytochemistry
Interference with other sciences including clinical chemistry, marine chemistry, medicinal chemistry, pharmaceutical chemistry

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In order to sustain the publishing process, each article accepted for publication in Open Chemistry is subject to an Article Processing Charge of €1200. This fee is used to cover the costs of the peer-review process, professional typesetting and copyediting, as well as online hosting, long-term preservation, and extensive promotion to potential readers. There is no submission fee. Information regarding payment of the charge will be provided following acceptance for publication. For more information please go to Article Processing Charges

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