Control of pesticide residues by liquid chromatography-mass spectrometry to ensure food safety

Liquid chromatography-mass spectrometry (LC-MS) has become an invaluable technique for the control of pesticide residues to ensure food safety. After an introduction about the regulations that highlights its importance to meet the official requirements on analytical performance, the different mass spectrometers used in this field of research, as well as the LC-MS interfaces and the difficulties associated with quantitative LC-MS determination, are discussed. The ability to use practical data for quantifying pesticides together with the option of obtaining structural information to identify target and non-target parent compounds and metabolites are discussed. Special attention is paid to the impact of sample preparation and chromatography on the ionization efficiency of pesticides from food. The last section is devoted to applications from a food safety point of view. (c) 2006 Wiley Periodicals, Inc.     

Why are some Spanish regions more resilient than others?

Which of a region's characteristics most strongly influence its degree of resilience? This study constructs a composite resilience index for the Spanish regions and uses Multiple Factor Analysis to compare it with the Martin resilience index (Martin, 2012). The results of a Principal Components Analysis to measure the relative contributions of potential regional resilience drivers indicate that, during recovery periods, it is market- service focused regional economies that show stronger resilience, while, in crisis periods, it is regions with a more highly-educated workforce.     

Application of factorial model for an optimization of partial replacement of feldspar by talc on the sintering process

This research used a factorial model containing two levels and three variables to evaluate the partial substitution of sodium feldspar (albite) by a talc ore found in abundance in the region of Itaiacoca—Brazil. The model can also be used to verify the influence of initial talc particle size, proportion, and sintering threshold temperature on the following physical properties, such as linear shrinkage, water absorption, bulk density, total porosity, and firing color. In this study, the mechanical strength of the compositions was evaluated by the flexural strength test. The factorial model indicated the sintering temperature as the variable that most affects the samples’ densification and the proportion of talc as the variable that changes the firing color. The experiment that used a higher sintering temperature combined with a coarser talc granulometry presented the highest mechanical strength. When more refined granulometry was used, there was the beginning of an overfire process. Water absorption values in the range of .04% and modulus of rupture of 49 MPa were obtained, confirming the talc's effectiveness as a secondary flux agent suitable for the formulation of ceramic bodies.     

Effect of calcium chloride and moderate shear on β-lactoglobulin aggregation in processing-like conditions

The influence of two variables (moderate shear and calcium chloride concentration) on the properties of β-lactoglobulin (β-lg) aggregate suspensions obtained by dynamic heat treatment (85 °C for 60 s) was studied. Variations in calcium chloride concentration from 5.1 to 7.1 mM were imposed, and led to major changes in the aggregate properties. The characterization of the aggregate size was performed using three distinct methods: laser granulometer, dynamic light scattering (DLS) and focus beam reflectance measurement (FBRM). Viscosity and residual native fraction were also determined. Statistical analysis of experimental data underlines the important combined effect of the two variables and paves the way for new ways of controlling the aggregate functionalities. The calcium chloride concentration has an effect on the entire aggregation process, from native β-lg to large aggregates. On the other hand, shear only impacts the formation of the large aggregates.     

Properties of carbon nanotube reinforced linear low density polyethylene nanocomposites fabricated by cryogenic ball‐milling

A cryogenic ball‐milling process to produce polymer/CNT nanocomposites was investigated. Linear low density polyethylene was used as the matrix material and 1 wt % of multiwalled carbon nanotubes (MWCNT) was used as reinforcement. The influence of the milling time and balls size was evaluated. The morphology of the nanocomposite and the degree of dispersion of the MWCNTs were studied using scanning electron microscopy (SEM), visual inspection, and light transmission microscopy; ropes as well as aggregates of MWCNTs were observed, and there was evidence of wetting of the nanotubes by the matrix polymer. An increase of up to 28% in the elastic modulus (determined by tensile testing) with respect to the matrix was obtained. Differential scanning calorimetry (DSC) analysis showed evidence of increase in the degree of crystallization, a result of the nucleating capability of the carbon nanotubes in the matrix. The degradation temperature of the nanocomposites does not show significant variations with respect to the unfilled polymer. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

The Discovery and Structure-Activity Evaluation of (+)-Floyocidin B and Synthetic Analogs

Tuberculosis represents one of the ten most common courses of death worldwide and the emergence of multidrug-resistant M. tuberculosis makes the discovery of novel anti-tuberculosis active structures an urgent priority. Here, we show that (+)-floyocidin B representing the first example of a novel dihydroisoquinoline class of fungus-derived natural products, displays promising antitubercular hit properties. (+)-Floyocidin B was identified by activity-guided extract screening and its structure was unambiguously determined by total synthesis. The absolute configuration was deduced from a key synthesis intermediate by single crystal X-ray diffraction analysis. A hit series was generated by the isolation of further natural congeners and the synthesis of analogs of (+)-floyocidin B. Extensive biological and physicochemical profiling of this series revealed first structure-activity relationships and set the basis for further optimization and development of this novel antitubercular scaffold.     

Thermal Behavior of Zein‐based Biodegradable Films

In previous work, zein was plasticized with oleic acid to obtain flexible films. However, it was observed that film properties were affected by the preparation method employed. Our objective was to investigate the effect of processing methods on thermal behavior of zein films by differential scanning calorimetry (DSC). Films containing 41% oleic acid were prepared by casting ethanol solutions of its components on flat surfaces or by extrusion of zein resins prepared by cold water precipitation of ethanol solutions of zein and oleic acid. Extrusion was carried out in single‐screw or twin‐screw extruders. Zein films were finished by hot rolling or heated in a Carver press. DSC thermograms showed large oleic acid melting peaks for cast films, smaller peaks for resin films, and no apparent peaks for heat‐treated samples. It was suggested that the resin formation process enhanced zein‐oleic acid interactions and promoted plasticization. All samples showed glass transitions at low temperatures.     

Quinoline-Dihydropyrimidin-2(1H)-one Hybrids: Synthesis,Biological Activity,and Mechanistic Studies

A novel class of quinoline-dihydropyrimidin-2(1H)-one (DHPM) hybrids was synthesized and in vitro antiplasmodial activity was evaluated against chloroquine sensitive (D10) and chloroquine resistant (Dd2) strains of Plasmodium falciparum, the human malaria parasite. The antiplasmodial activity was compared to previously reported DHPM based molecular hybrids. Dual mode of antiplasmodial action of the most active member has been evaluated through heme binding study and in silico docking in the active site of dihydrofolate enzymes (wild-type as well as mutant). Favourable pharmacokinetic parameters were predicted in the ADMET evaluation. The new hybrids were also tested against a number of DNA and RNA viruses. No antiviral activity was found, except for one hybrid that showed mild inhibitory activity against two strains of cytomegalovirus (AD-169 and Davis), The most active hybrid was found to be a selective inhibitor of the growth of P. falciparum as well as a modest inhibitor of varicella zoster virus in HEL cells. Cytotoxicity of all hybrids was assessed in HEL, HeLa, Vero, MDCK, and CRFK cell cultures.