Evaluation of multiple solid-phase microextraction as a technique to remove the matrix effect in packaging analysis for determination of volatile organic compounds

Multiple solid-phase microextraction (SPME) is an useful technique for the direct quantification of solid samples removing any matrix effect. The volatile organic compounds formed in the extrusion-coating process of multilayer packaging materials have already been quantified by multiple HS-SPME coupled to gas chromatography (GC)-mass spectrometry (MS) using volatile organic compound (VOC) solutions in hexadecane for calibration. In this article, water is proposed as solvent to prepare the calibration solutions because it provides a shorter calibration time, better linearity, better reproducibility, and lower detection limits than hexadecane. Besides, the extraction of VOCs from aqueous solutions is exhaustive and avoids the extrapolations needed to calculate the total peak areas, as they can be calculated as the sum of the individual areas of each extraction. Finally, it is checked whether the two solvents provide the same mean values for the total peak areas.     

Supercritical fluid extraction of phenol compounds from olive leaves

A clean, highly selective supercritical fluid extraction (SFE) method for the isolation of phenols from olive leaf samples was examined. Total phenol extracts were determined using the Folin-Ciocalteu reagent. Dried, ground, sieved olive leaf samples (30 mg) are subjected to SFE, using carbon dioxide modified with 10% methanol at 334 bar, 100 degrees C (CO(2) density 0.70 g ml(-1)) at a liquid flow-rate of 2 ml min(-1) for 140 min. Diatomaceous earth is used to reduce the void volume of the extraction vessel. The influence of extraction variables such as modifier content, pressure, temperature, flow-rate, extraction time, and collection/elution variables, were studied. Supercritical fluid extracts were screened for acid compounds such as carboxylic acids and phenols using Electrospray-MS (in the negative ionization mode). SFE was found to produce higher phenol recoveries than sonication in liquid solvents such as n-hexane, diethyl ether and ethyl acetate. However, the extraction yield obtained was only 45%, using liquid methanol.     

Capillary electrophoretic separation of mono- and dimaltosyl-β-cyclodextrins and determination of the stability constants of their benzoate complexes

Summary Capillary zone electrophoresis method has been developed for the separation (and determination) of monoand dimaltosyl-β-cyclodextrins using indirect UV absorbance detection. The separation is based on inclusion complex formation with benzoate ion which is used as background electrolyte and absorbance provider simultaneously. Good resolution of cyclodextrin mixtures can be achieved optimizing the pH and the benzoic acid concentration in the background electrolyte. Capillary zone electrophoresis method has also been developed for the determination of formation constants of inclusion complexes.     

Classical ceramic colors through colloidal and from alkoxides gels

Classical ceramic pigments are manufactured through the traditional method of firing a mixture of oxides previously mechanical homogeneized in a mill. From industrial overview sol-gel applied in ceramic pigments manufacture is more expensive than ceramic method because the high price of raw materials. However in some classical pigments it would be economically interesting to use a sol-gel route because raw materials in ceramic route are as well expensive and gel route give the pigment at lower firing temperature and soaking time. In this paper a discussion for several pigments is presented.     

Decision taking under pressure: Evidence on football manager dismissals in Argentina and their consequences

The paper focuses on dismissals of football managers and whether such decisions appear to contribute to organisational goals or else to be fruitless exercises in scapegoating. Its empirical setting is Argentina where incidence of sackings is more than one per season per club. It models 20 years of football match results and detects a tendency for a change of manager to be followed by deterioration in team performance, with adverse effects concentrated in results of matches played away. The evidence is consistent with decisions being driven by fan and media pressure rather than in realistic hope of improving the position of the club.     

Determination of brominated diphenyl ethers (from mono- to hexa- congeners) in indoor dust by pressurised liquid extraction with in-cell clean-up and gas chromatography–mass spectrometry

This study presents a selective pressurised liquid extraction (PLE) and gas chromatography–mass spectrometry/mass spectrometry method for the determination of brominated diphenyl ethers (BDEs) in indoor dust. Selective PLE consisted of the addition of Florisil mixed with the sample in order to perform an in-cell clean-up. This approach provided a cleaner and almost colourless extract, ready to be injected in the gas chromatograph. The PLE conditions were studied using an experimental design, firstly a 4 × 3 × 2 multifactor categorical design to screen sorbent, solvent and temperature and then a central composite design to optimise sorbent mass, temperature and time. Finally, the number of extraction cycles was studied. The selected conditions were 4 g of Florisil all mixed with the sample and no additional clean-up sorbent layer, 1:1 n-hexane-dichloromethane, 60% flush volume, 40 °C, 1,500 psi, 2-min static time and one cycle. The proposed method allowed accurate determination of BDEs, with recovery values between 82% and 101% and detection limits between 0.06 and 0.24 ng g⁻¹. It also has advantages over other existing methods in terms of simplicity, automation, analysis time and solvent consumption.     

Synthesis of Gray Ceramic Pigments with Rutile Structure from Alkoxides

In this study, V _x Ti_{1 – x} O₂ (0 x 0.20) rutile solid solutions have been synthesized from gels built from hydrolysis-condensation of V(IV) oxyacetilacetonate and Ti(IV) isopropoxide mixture (polymeric gel). These solid solutions are stable at high temperature (1200–1400°C) and into glazes. The colouration of the glazes together with the thermal stability of these rutile solid solutions indicates their potential usefulness as gray ceramic pigments. The results obtained are compared with those obtained from V₂O₅ and TiO₂ (anatase) mixtures (ceramic method). From alkoxides, noticeable change in coloration is obtained on glazes, when x < 0.10.     

Fe x Ti1−2x M x O2 (M=Nb,Ta) rutile solid solutions from gels

In this study, Fe _x Ti_1–2x M _x O₂ (M=Nb, Ta) rutile solid solutions have been synthesized from gels made from Fe(III) acetylacetonate, NbCl₅, TaCl₅, Ta(V) ethoxide, TiCl₄ and Ti(IV) isopropoxide. The results obtained are compared with those obtained by the ceramic method. The solid solutions synthesized from gels were obtained at lower temperatures than these synthesized by the ceramic method.     

Two-dimensional analysis of bar-and-joint assemblies on a sphere: Equilibrium,compatibility and stiffness

This paper discusses a 2D truss formulation with spherical angular variables for bar-and-joint assemblies existing in 3D on the surface of a sphere. Based on the principle of potential energy, coupled problems of equilibrium and compatibility, as well as of stiffness and prestress stability are investigated. Finally, the results are illustrated by numerical examples.