Sample Preparation for the Determination of Metals in Food Samples Using Spectroanalytical Methods—A Review

Abstract

The present article gives an overview of recent publications and modern techniques of sample preparation for food analysis employing atomic and inorganic mass spectrometric techniques, such as flame atomic absorption spectrometry, chemical vapor generation atomic absorption and atomic fluorescence spectrometry, graphite furnace atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry. Among the most frequently applied sample preparation techniques for food analysis are dry ashing, usually with the addition of an ashing aid, and acid digestion, preferably with the assistance of microwave energy. Slurry preparation, particularly with the assistance of ultrasound, is increasingly used to reduce acid consumption and sample preparation time. Direct analysis of solid samples is gaining importance in the field of food analysis as it offers the highest sensitivity, avoids the use of acids and other aggressive reagents, makes possible the analysis of micro‐samples, and can be applied for fast screening analysis, e.g., of fresh meat.     

A Robertson-type uncertainty principle and quantum Fisher information

Let A₁,…,A_N be complex self-adjoint matrices and let ρ be a density matrix. The Robertson uncertainty principle

     

Finite Element Analysis of General Magnetomechanical Coupling Phenomena

In this paper we consider the derivation of a finite element model for fully–coupled magneto–mechanical boundary value problems based on a vector–valued magnetic potential. The formulation allows for the incorporation of nonlinear, anisotropic and hysteretic constitutive response. A piezomagnetic inclusion problem is computed to test the implementation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The a.c. susceptibility third harmonic component of NdO1−0.14F0.14FeAs: A flux dynamic magnetic analysis

In this contribution we present the analysis of the third harmonic susceptibility data of the new superconductor NdFeAs_1−0.14F_0.14. ‘Cole-Cole’ polar plots respect to the magnetic frequency of the exciting field are presented and discussed. Data show that NdFeAs_1−0.14F_0.14 exhibit a ‘bulk pinning’ with a 3D flux dynamic character. A comparison of the responses of high T_c materials and an evaluation of theoretical critical states is also presented.     

Cancer Initiation,Progression and Resistance: Are Phytocannabinoids from Cannabis sativa L. Promising Compounds?

Cannabis sativa L. is a source of over 150 active compounds known as phytocannabinoids that are receiving renewed interest due to their diverse pharmacologic activities. Indeed, phytocannabinoids mimic the endogenous bioactive endocannabinoids effects through activation of CB1 and CB2 receptors widely described in the central nervous system and peripheral tissues. All phytocannabinoids have been studied for their protective actions towards different biological mechanisms, including inflammation, immune response, oxidative stress that, altogether, result in an inhibitory activity against the carcinogenesis. The role of the endocannabinoid system is not yet completely clear in cancer, but several studies indicate that cannabinoid receptors and endogenous ligands are overexpressed in different tumor tissues. Recently, in vitro and in vivo evidence support the effectiveness of phytocannabinoids against various cancer types, in terms of proliferation, metastasis, and angiogenesis, actions partially due to their ability to regulate signaling pathways critical for cell growth and survival. The aim of this review was to report the current knowledge about the action of phytocannabinoids from Cannabis sativa L. against cancer initiation and progression with a specific regard to brain, breast, colorectal, and lung cancer as well as their possible use in the therapies. We will also report the known molecular mechanisms responsible for such positive effects. Finally, we will describe the actual therapeutic options for Cannabis sativa L. and the ongoing clinical trials.     

Investigation of catalytic activities by differential thermal analysis

A calorimetric method is proposed to evaluate the catalytic activity of a solid catalyst with respect to the exothermic oxidation of Volatile Organic Compounds (VOC).This method employs a differential thermal analyzer in which an inert reference and a catalytically active sample are both fluxed at a constant rate with a reactive gaseous mixture composed of an inert gas (N₂ 90% vol.), oxygen and VOC, the last typically 900 to 5000 ppm. While the temperature is varied according to a predefined cycle, the output signal due to the exothermic reaction on the catalyst is continuously recorded. The design of the test chamber, the amount of catalyst, the shape of the holders and finally the flow rate and composition of the gaseous mixture should be carefully selected in order to achieve reproducible results.     

Selective Detection of Mg2+ for Sensing Applications in Drinking Water

A new series of ligands containing the 2-(2-hydroxy-3- naphthyl)-4-methylbenzoxazole (HNBO) fluorophore showed selectivity for Mg²⁺ ions, without the interference of Ca²⁺. The most promising representative L3 resulted the best performing sensor for Mg²⁺ both in solution and embedded in an all-solid-state optode, especially towards real samples of drinkable water.     

Poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan Aqueous Dispersions: Toward Electrically Conductive Bioactive Materials for Neural Interfaces

There is an actual need of advanced materials for the emerging field of bioelectronics. One commonly used material is the conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) due to its general use in organic electronics. However, depending on the application in bioelectronics, PEDOT:PSS is not fully biocompatible due to the high acidity of the residual sulfonate protons of PSS. In this paper, the synthesis and biocompatibility properties of new poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan (PEDOT:GAG) aqueous dispersions and its resulting films are shown. Thus, negatively charged GAGs as an alternative to PSS are presented. Three different commercially available GAGs, hyaluronic acid, heparin, and chondroitin sulfate are used. Indeed, PEDOT:GAGs dispersions are prepared through an oxidative chemical polymerization in water. Biocompatibility assays of the PEDOT:GAGs coatings are performed using SH‐SY5Y and CCF‐STTG1 cell lines and with ATP and Ca²⁺. Results show full biocompatibility and a pronounced anti‐inflammatory effect. This last characteristic becomes crucial if implanted in the body. These materials can be used for in vivo applications, as transistor or electrode for electrical recording and for all the possible situations when there is contact between electronic circuits and living tissues.

     

Aggregation tendency and reactivity toward AgX of cationic half-sandwich ruthenium(II) complexes bearing neutral N,O-ligands

The aggregation tendency of complexes [Ru(eta6-cymene)(N,O)Cl]X [N,O = 2-benzoylpyridine (2-bzpy), 1, and 2-acetylpyridine (2-acpy), 2, X- = BPh4- or PF6-] has been studied by means of PGSE NMR experiments. It was found that complexes with PF6- as counterion are mainly present in CD2Cl2 as ion pairs at low concentration, as a mixture of ion triples and free anions at medium concentration and as ion quadruples at elevated concentration. 19F, 1H-HOESY NMR experiments revealed that in ion triples and ion quadruples two cationic Ru-units pair up. Consistently, in the solid-state structure of 1PF6, determined through X-ray single-crystal investigation, two cationic Ru-units are held together by an intermolecular pi-pi stacking interaction between the pyridyl rings. Complexes having BPh4- as counterion are only present in solution as even aggregates, namely ion pairs at low concentration and ion quadruples at elevated concentration. In such a case a counteranion bridges two cationic Ru-units as observed in the solid-state structure of 1BPh4. The reactivity of complexes 1-2 toward AgX salts has been investigated in different solvents. Bicationic [Ru(eta6-cymene)(N,O)(MeCN)]X2 (N,O = 2-bzpy, 3, and 2-acpy, 4) and [Ru(MeCN)4(N,O)]X2 (N,O = 2-bzpy, 5, and 2-acpy, 6) complexes were obtained by the reaction of 1 and 2 with AgX in the presence of three equivalents of acetonitrile or in acetonitrile, respectively. The reaction of 1 with AgPF6 in acetone afforded complex [Ru(eta6-cymene)(N,O,O)]PF6 (7, where N,O,O = 4-alcoxide-4-phenyl-4-(pyridin-2-yl)butan-2-one) from the C-C coupling of a deprotonated methyl group of the coordinated acetone and the C=O moiety of 2-bzpy ligand.