Automated on-line gel permeation chromatography-gas chromatography for the determination of organophosphorus pesticides in olive oil

An on-line combination of gel permeation chromatography and gas chromatography has been designed using either a laboratory-built or a commercially available LC-GC apparatus to determine organophosphorus pesticides in olive oil. Gel permeation chromatography was used for sample pretreatment, viz. to separate the low-molecular-mass pesticides from the higher-molecular-mass fat constituents of the oil. A mixture of n-decane and the azeotropic mixture of ethyl acetate and cyclohexane was found to give an adequate separation between the fat and the organophosphorus pesticides. The pesticide-containing fraction, monitored by a UV detector, was transferred on-line to the gas chromatograph using a loop-type interface. n-Decane (6%, v/v) was added to the eluent in order to widen the application range of the transfer technique towards more volatile pesticides. After solvent evaporation through the solvent vapour exit and subsequent GC separation, the compounds were selectively detected with a thermionic or a flame photometric detector. The set-up allowed the direct analysis of oil samples after dilution in the gel permeation chromatography eluent without further sample clean-up. Detection limits were about 5 and 10 μg/kg with the thermionic and the flame photometric detector, respectively, when using an injection volume of only 30 μl of the 20-fold diluted oil. The total procedure was linear in the 0.01–10 mg/kg range for both detectors. For twenty organophosphorus pesticides, the relative standard deviations were 3–13% at the 20–60 μg/kg level.     

Cyclopentadienyl, indenyl, and fluorenyl complexes of sodium with 15-crown-5

The sodium complexes [NaC₅H₅(15-crown-5)] (1a), [NaC₉H₇(15-crown-5)] (1b), and [NaC₁₃H₉(15-crown-5)] (1c, C₅H₅=cyclopentadienyl, C₉H₇=indenyl, C₁₃H₉=fluorenyl) were synthesized from NaC₅H₅, NaC₉H₇, NaC₁₃H₉, and 15-crown-5. Single crystal X-ray diffraction analyses were carried out for all three compounds 1a, 1b, 1c, and show that monomeric units were present in the solid state with the organic aromatic anion coordinated to the sodium cation via the five-membered ring.     

Surface enhanced infrared absorption on Au nanoparticle films deposited on SiO2/Si for optical biosensing: Detection of the antibody-antigen reaction

The specific antibody-antigen reaction was detected by taking advantage of the effect of surface enhanced infrared absorption (SEIRA). For the SEIRA active film, single Au nanoparticles (AuNP) deposited on the SiO₂/Si wafer surface were used. After immobilizing specific antibodies onto the AuNP, these samples were then exposed to specific antigens (unspecific antigens, respectively); then the samples were investigated with infrared spectroscopy. In addition, the same kind of sample preparation was done using a 40 nm thick non-enhancing Au film, in order to compare the SEIRA transmission spectra to the infrared reflection absorption spectra (IRRAS) and therefore to determine the factor of the SEIRA enhancement. In both geometries, SEIRA transmission and IRRAS, the antibody-antigen coupling could clearly be detected; a comparison of the spectra showed, that the enhancement factor due to the Au nanoparticles is roughly 25.     

Comparison of different technologies for alginate beads production

This paper describes the results of the round robin experiment “Bead production technologies” carried out during the COST 840 action “Bioencapsulation Innovation and Technologies” within the 5th Framework Program of the European Community. In this round robin experiment, calcium alginate hydrogel beads with the diameter of (800 ± 100) μm were produced by the most common bead production technologies using 0.5–4 mass % sodium alginate solutions as starting material. Dynamic viscosity of the alginate solutions ranged from less than 50 mPa s up to more than 10000 mPa s. With the coaxial air-flow and electrostatic enhanced dropping technologies as well as with the JetCutter technology in the soft-landing mode, beads were produced from all alginate solutions, whereas the vibration technology was not capable to process the high-viscosity 3 % and 4 % alginate solutions. Spherical beads were generated by the electrostatic and the JetCutter technologies. Slightly deformed beads were obtained from high-viscosity alginate solutions using the coaxial airflow and from the 0.5 % and 2 % alginate solutions using the vibration technology. The rate of bead production using the JetCutter was about 10 times higher than with the vibration technology and more than 10000 times higher than with the coaxial air-flow and electrostatic technology. In memory of our colleague Stefan Rosinski     

Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand‐Directed Modulation

Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano‐sized highly‐active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser‐generated inorganic‐salt‐stabilized metal nanoparticles, various impurity‐free NMAs (Au, Pd, and Au‐Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond.     

On optimal allocation of risk vectors

In this paper we extend results on optimal risk allocations for portfolios of real risks w.r.t. convex risk functionals to portfolios of risk vectors. In particular we characterize optimal allocations minimizing the total risk as well as Pareto optimal allocations. Optimal risk allocations are shown to exhibit a worst case dependence structure w.r.t. some specific max-correlation risk measure and they are comonotone w.r.t. a common worst case scenario measure. We also derive a new existence criterion for optimal risk allocations and discuss some examples.     

Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand-Directed Modulation

Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano-sized highly-active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser-generated inorganic-salt-stabilized metal nanoparticles, various impurity-free NMAs (Au, Pd, and Au-Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond.     

Non‐Covalently Stabilized Alginate Hydrogels as Functional Cell Scaffold Material

Biopolymers are an attractive class of compounds for being used in biomedical applications as they are widely available from biomass. Their drawback is the lack of mechanical stability and the ability to tune this properly. Covalent chemical cross‐linking is an often used approach but it limits usability due to legislation as well as the need of advanced and specialized knowledge by end users such as clinicians. Here, increased and tunable mechanical properties are achieved of alginate‐based hydrogels with non‐covalent approaches using linear polyethyleneimine (LPEI) as a polyelectrolyte rather than only multivalent metal ions (Ca²⁺). Gel stiffness increases with increasing LPEI content. Gel morphology changes from a thin fibrous mesh for alginate‐Ca²⁺ to thicker fibrous networks when LPEI is introduced. The gels are able to efficiently release encapsulated small molecular dyes and the gels are able to host cells. For the cell encapsulation human skin fibroblasts (HSkF) and human bone marrow‐derived mesenchymal stem cells (hBM‐MSC) are used. HSkF can be successfully incorporated without diminished viability while the matrix components and gel preparation method are not compatible with hBM‐MSC. The newly developed alginate‐based system is regarded as a potential candidate for wound dressing materials.