A Microbial Sensor Based on Direct Electron Transfer at Shewanella Sp. Drop‐Coated Screen‐Printed Carbon Electrodes

Aerobically grown Shewanella sp. bacterial suspension drop‐coated on a disposable screen‐printed carbon electrode was found to possess electroactivity without the aid of redox mediator. Cyclic voltammetric studies revealed the characteristics of a mixed diffusion adsorption‐controlled electrochemical process for direct electron transfer at the bacteria‐modified electrode. Both FE‐SEM and ATR FT‐IR experiments were carried out to investigate the surface characteristics. The electroanalytical applicability was further demonstrated for electrocatalytic reduction of arsenite, hydrogen peroxide and nitrite. Low cost and very simple manufacturing procedure allow for the proposed bacterial sensor to be applied as disposable devices.     

HPLC-MS/MS enantioseparation of triazole fungicides using polysaccharide-based stationary phases

The enantiomeric separation of 21 triazole fungicides was carried out on four polysaccharide-derived chiral stationary phases in the reversed phase separation mode using high performance liquid chromatography coupled with tandem mass spectrometry. All fungicides were detected in electrospray ionization (ESI) positive mode with selected reaction monitoring (SRM). Complete enantioseparation was achieved for 21 fungicides except for difenoconazole based on cellulose tris (3,5-dimethylphenylcarbamate) and cellulose tris (3-chloro-4-methylphenyl carbamate) columns by optimizing experimental conditions including mobile phase and column temperature. Mobile phase was 0.1% formic acid aqueous solution mixed with methanol or acetonitrile in different proportions. Among all the fungicides, 15 with two enantiomers and three with four stereoisomers (bitertanol, bromuconazole, and cyproconazole) were successfully separated at 25°C. Enantioseparation for the other three fungicides (propiconazole, triadimenol, and difenoconazole) with four stereoisomers could be achieved by changing the column temperature from 10 to 40°C. Propiconazole and triadimenol were enantioseparated on baseline at 40 and at 35°C, respectively, and difenoconazole was enantioseparated partially with the R(s) > 1.1 at 25°C. Moreover, linearities and limits of detection (LODs) of 21 fungicides except for difenoconazole were studied, showing coefficients of determination (R(2)) higher than 0.99 and LODs lower than 2.5 μg/L.     

Prediction of the pH‐rate profile for dimethyl sulfide oxidation by hydrogen peroxide: The role of elusive H3O2+ Ion

Experimental kinetics of sulfide oxidation by hydrogen peroxide presents a pH‐dependent profile. In this article, it was carried out a detailed study of the mechanism and kinetics of dimethyl sulfide (DMS) oxidation by H₂O₂ in neutral, acid, and basic aqueous medium using ab initio calculations. The results point out that DMS oxidation in neutral aqueous medium occurs through its direct reaction with H₂O₂. In acid medium, cluster‐continuum model calculations shows that cluster is the best representation of the very reactive species. In basic medium, there is formation of the species. However, the pathway involving this species has high free energy barrier, making this pathway unfeasible. The theoretical pH‐rate profile is in good agreement with the experimental observations. © 2013 Wiley Periodicals, Inc.     

Ultrathin Alternating Copolymer Nanotubes with Readily Tunable Surface Functionalities

Well‐defined ultrathin nanotubes (30 nm in diameter and of micrometer‐scale length) were generated through the self‐assembly of a novel alternative copolymer synthesized using an epoxy–thiol click‐chemistry reaction. The self‐assembly mechanism was investigated both by experiments and using dissipative particle dynamics (DPD) simulations. The obtained nanotubes can be readily functionalized with carboxy groups, amino groups, peptides, or other groups by simple modular click copolymerization.     

Fast gas chromatography-negative-ion chemical ionization mass spectrometry with microscale volume sample preparation for the determination of benzodiazepines and alpha-hydroxy metabolites, zaleplon and zopiclone in whole blood

Fast gas chromatography/negative-ion chemical ionization mass spectrometric (GC/NICI-MS) assay combined with rapid and nonlaborious sample preparation is presented for the simultaneous determination of benzodiazepines and alpha-hydroxy metabolites, zaleplon and zopiclone in whole blood. The compounds were extracted from 100 microl of whole blood by simultaneous multitube, microscale liquid-liquid extraction (LLE) and derivatized by N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA), without the need for the time-consuming concentration stage. In the analytical separation, various parameters of fast GC/NICI-MS were applied, e.g. the use of hydrogen as a GC carrier gas, a high carrier gas velocity, a small film thickness of the analytical column, fast MS data acquisition, fast temperature ramping, and high initial and final temperatures of GC column. Sensitive identification, screening and quantitation of 18 compounds of interest were achieved in chromatographic separation in only 4.40 min. Accurate and reproducible results were obtained by using five different and carefully selected deuterated analogues on the basis of the chemical properties of the target analytes. Nevertheless, for alpha-OH-midazolam, and for bromazepam and flunitrazepam at low concentrations, the results can be considered only semiquantitative on the basis of the validation data. The extraction efficiencies ranged from 74.3 to 105.7% and the limits of quantitation (LOQ) from 1 to 100 ng ml(-1). Rapid sample preparation and fast chromatographic separation allowed cost-efficient, reliable and high sample-throughput analyses with a low amount of manual work. The method was fully validated and accredited according to EN ISO/IEC 17025 standards and is applicable for sensitive, reliable and quantitative determination of benzodiazepines, zaleplon and zopiclone, e.g. in clinical and forensic toxicology.     

Mesoporous materials for drug delivery

Research on mesoporous materials for biomedical purposes has experienced an outstanding increase during recent years. Since 2001, when MCM-41 was first proposed as drug-delivery system, silica-based materials, such as SBA-15 or MCM-48, and some metal-organic frameworks have been discussed as drug carriers and controlled-release systems. Mesoporous materials are intended for both systemic-delivery systems and implantable local-delivery devices. The latter application provides very promising possibilities in the field of bone-tissue repair because of the excellent behavior of these materials as bioceramics. This Minireview deals with the advances in this field by the control of the textural parameters, surface functionalization, and the synthesis of sophisticated stimuli-response systems.     

Triclosan‐based antibacterial paper reinforced with nano‐montmorillonite: a model nanocomposite for the development of new active packaging

In this study, a suitable method is reported to produce reinforced antibacterial paper packaging using the antimicrobial triclosan (TC) and organically modified montmorillonite (OMMT) as “model” compounds. Direct incorporation of TC at a concentration of 1 wt% and OMMT at concentrations of 1, 4, 7, and 10 wt% into papers was performed via coating process, and the resulting materials were characterized by in vitro antimicrobial assays, thermogravimetric analysis, scanning electron microscopy, mechanical tests, and water vapor transmission rate determinations. It was demonstrated that the presence of 1% TC in the coated papers exhibited inhibitory effects against Staphylococcus aureus and Escherichia coli. It was also pointed out that increases of approximately 30% in the tensile strength of commercial paper are obtained by using the OMMT at a concentration of 1 wt%. Water barrier property and thermal stability of paper were also enhanced because of the coating process and the incorporation of OMMT. The results from this study demonstrate that OMMT has a great potential to be incorporated into coating formulations to obtain antibacterial‐coated papers with improved properties for various packaging applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Ionic Liquids for and by Analytical Spectroscopy

Abstract

In this mini‐review we highlight two aspects of ionic liquids that to date have either no or limited studies. They are (1) exploitation of unique features of ionic liquids to develop novel spectroscopic methods and (2) development of novel spectroscopic methods, for the sensitive and accurate determination of thermal physical properties of ionic liquids. In the first category, we will describe several novel methods which were developed utilizing unique properties of ionic liquids for measurements which are not possible otherwise. They include the sensitive and accurate method to determine enantiomeric compositions of a variety of pharmaceutical products with different size, shape, and functional groups. This method is based on the use of a chiral IL which serves both as a solvent and also as a chiral selector. Ionic liquids have also been successfully used to substantially enhance the sensitivity of thermal lens measurements. In the second category, we will describe recent development in which transient grating technique and thermal lens technique have been successfully used for the sensitive, accurate, nondestructive determination of thermal physical properties of ILs.     

Metal‐Free Catalyst for the Chemoselective Methylation of Amines Using Carbon Dioxide as a Carbon Source

N‐methylation of amines is an important step in the synthesis of many pharmaceuticals and has been widely applied in the preparation of other key intermediates and chemicals. Therefore, the development of efficient methylation methods has attracted considerable attention. In this respect, carbon dioxide is an attractive C₁ building block because it is an abundant, renewable, and nontoxic carbon source. Consequently, we developed a highly chemoselective, metal‐free catalytic system that operates under ambient conditions for the N‐methylation of amines.