A novel total reflection X-ray fluorescence procedure for the direct determination of trace elements in petrochemical products

A total reflection X-ray fluorescence (TXRF) procedure was developed for the determination of metal traces in petrochemical end products or intermediates for surfactant synthesis. The method combines a fast and straightforward sample preparation, i.e. deposition on the sample holder and evaporation of the sample matrix, with an efficient quantification method based on internal standardization (organic gallium standard). The method developed showed detection limits below 0.05 μg g^-1 and in most cases below 0.005 μg g^-1. Fifteen elements (Ca, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rh, Sn, Sr, V and Zn) were determined in matrices such as paraffins, n-olefins, linear alkylbenzenes, long-chain alkyl alcohols and esters: typical metal contents were below 1 μg g^-1. The results were compared with the reference method ASTM D5708 (test method B) based on inductively coupled plasma optical emission spectroscopy: advantages and drawbacks of the two procedures were critically evaluated. The TXRF method developed showed comparable precision and absence of bias with respect to the reference method. A comparison of the performances of the two methods is presented.     

Review: multistage mass spectrometry in quality, safety and origin of foods

Quality and safety control and the validation of origin are hot issues in the production of food and its distribution, and are of primary concern to food and agriculture organization. Modern mass spectrometry (MS) provides unique, reliable and affordable methodologies to approach with a high degree of scientificity any problem which may be posed in this field. In this review the contribution of mass spectrometry to food analysis is presented aiming at providing clues on the fundamental role of the basic principles of gas-phase ion chemistry in applied research fields. Applications in proteomics, allergonomics, glycomics, metabolomics, lipidomics, food safety and traceability have been surveyed. The high level of specificity and sensitivity of the MS approach allows the characterization of food components and contaminants present at ultra-trace levels, providing a distinctive and safe validation of the products.     

Fullerenol entrapment in calcite microspheres

Hybrid microspheres of calcium carbonate/fullerenol were synthesized and characterized. Their morphology depends on the concentration of the fullerenol solutions. XRD and FT-IR measurements proved that the mineral phase is consistently calcite, while fluorescence confocal microscopy indicated that fullerenol is homogenously included in the crystalline matrix.     

Dye-Doped Silica Nanoparticles for Enhanced ECL-Based Immunoassay Analytical Performance

The combination of highly sensitive techniques such as electrochemiluminescence (ECL) with nanotechnology sparked new analytical applications, in particular for immunoassay-based detection systems. In this context, nanomaterials, particularly dye-doped silica nanoparticles (DDSNPs) are of high interest, since they can offer several advantages in terms of sensitivity and performance. In this work we synthesized two sets of monodispersed and biotinylated [Ru(bpy)₃]²⁺-doped silica nanoparticles, named bio-Triton@RuNP and bio-Igepal@RuNP, obtained following the reverse microemulsion method using two different types of nonionic surfactants. Controlling the synthetic procedures, we were able to obtain nanoparticles (NPs) offering highly intense signal, using tri-n-propylamine (TPrA) as coreactant, with bio-Triton@RuNps being more efficient than bio-Igepal@RuNP.     

Weighted power counting and Lorentz violating gauge theories. I: General properties

We construct local, unitary gauge theories that violate Lorentz symmetry explicitly at high energies and are renormalizable by weighted power counting. They contain higher space derivatives, which improve the behavior of propagators at large momenta, but no higher time derivatives. We show that the regularity of the gauge-field propagator privileges a particular spacetime breaking, the one into space and time. We then concentrate on the simplest class of models, study four dimensional examples and discuss a number of issues that arise in our approach, such as the low-energy recovery of Lorentz invariance.     

Mild and convenient one-pot synthesis of 1,3,4-oxadiazoles

A mild, general, convenient, and efficient one-pot synthesis of 2-phenyl-5-substituted-1,3,4-oxadiazoles is described. Both (hetero)aryl and alkyl carboxylic acids were efficiently condensed with benzohydrazide in the presence of TBTU to give diacylhydrazine intermediates. The latter underwent a smooth TsCl-mediated cyclodehydration reaction to afford 2-phenyl-5-substituted-1,3,4-oxadiazoles in good to very good yields.     

Stereochemistry of allenic compounds : Absolute configuration of cycloallenols and cycloallenones

The absolute configuration of α-cycloallenols (3 and 4)as well as of α-cycloallenones(1)has been correlated to that of cyclic alkenols (2) by chemical transformations.