Determination of cadmium (II) and zinc (II) in olive oils by derivative potentiometric stripping analysis

A method for the determination of cadmium (II) and zinc (II) in olive oils by derivative potentiometric stripping analysis after dry ashing of the sample is described. The metal ions were concentrated as their amalgams on a glassy carbon working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. Potential and time data were digitally converted into dt dE 121, and E was plotted vs. dt dE 121, thus increasing sensitivity of the method and improving resolution of the analysis. Quantitative analysis was carried out by the method of standard additions; a good linearity was obtained in the range of concentrations examined. Recoveries of 92\u2013102% for cadmium (II) and of 89\u201399% for zinc (II) were obtained from an olive oil spiked at different levels. The detection limits were 5.1 ng g 121 for cadmium (II) and 7.6 ng g 121 for zinc (II)

High performance liquid chromatographic determination of 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde in honey

A method of determination of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in honey by high-performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided and direct injection of the sample into the HPLC system is allowed. The procedure offers a high specificity, since the derivatives of F and HMF are well separated from the other components of the mixture under examination. Recoveries of 95-99% were obtained from honey spiked at different levels with both analytes. The detection limit is of the order of 10 \u3bcg/kg of honey and reproducibility (mean of six determinations) is \ub13% for F and \ub12% for HMF

High performance liquid chromatographic determination of 2-furaldehyde and 5- hydroxymethyl-2-furaldehyde in fruit juices

A method for the determination of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in fruit juices by high-performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided; and direct injection of the sample into the HPLC system is allowed. The procedure offers a high specificity and a detection limit of the order of 10\u20138 mol/L. Recoveries of 95-98% are obtained from apple juice spiked at different levels with both analytes. The reproducibility (mean of six determinations) is \ub1 2% for F and \ub1 3% for HMF

High performance liquid chromatographic determination of 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde in processes citrus juices

The occurrence of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in processed citrus juices is an indication of quality deterioration. A close relationship between flavor changes and F content exists, while HMF can give rise to browning reactions. Both F and HMF are formed during heat processing or storage at improper temperatures. The detection of these compounds becomes more and more important as aseptic processing and packaging of citrus juices are becoming widespread. Aseptic packaging allows higher temperatures during distribution and storage to be employed without microbial spoilage, but off-flavors develop as citrus products are exposed to these conditions. In this paper a method of determination by high performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided, and direct injection of the sample into the HPLC system is allowed. The determination offers a high specificity and a detection limit of the order of 10-8 mol/l for both analytes. Recoveries from an orange juice spiked at different levels are quantitative. Reproducibility data are presented

High-performance liquid chromatographic determination of 2-furaldehyde in spirits

Official methods for the determination of 2-furaldehyde in spirits involve for a spectrophotometric evaluation, which is characterized by poor specificity. Gas chromatographic evaluations have also been proposed, which offer a much higher sensitivity, particularly when capillary columns are used. In this paper a high-performance liquid chromatographic (HPLC) method based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives is described. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives is avoided, and direct injection of the sample into the HPLC system is allowed. The determination offers a high specificity and a detection limit of the order of 10-8 mol/l. Accuracy and reproducibility data are presented

THE DEVELOPMENT OF CHILDREN’S IDENTIFICATION: A CROSS-CULTURAL COMPARISON BETWEEN BULGARIA, ITALY AND UKRAINE

The study presented here analyses the development of self-categorisation, national, European and local identification of Bulgarian, Ukrainian and Italian children and adolescents growing up in Bulgaria, Ukraine and Italy. The sample consisted of 541 children aged 6, 9, 12 and 15 years. It was found that national, European and local identifications differ in the three national groups. It is argued that the cognitive-developmental account of the development of national identification is unable to explain the patterns of findings which were obtained. The social identity theory, however, is able to explain the different patterns of importance given to the different identifications by the three national groups

Characterisation of Columbite-Tantalite (Coltan) ore from Congo. Elemental composition by total reflection X-ray fluorescence analysis

The paper describes the analysis of a columbite-tantalite (coltan) mineral ore from Congo by using total reflection X-ray fluorescence (TRXRF) analysis. The sample was mineralised with a lithium tetraborate and lithium metaborate flux mixture. TRXRF allows multi-element analysis in a wide range of concentrations. The results were in good agreement with those obtained by using another alkaline fusion with sodium peroxide

Determination of cadmium (II) and lead (II) in whole and skim milk by stripping chronopotentiometric analysis

A method for the determination of cadmium (II) and lead (II) in whole and skim milk by stripping chronopotentiometric analysis is described. The metal ions were concentrated as their amalgams on a glassy carbon working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. Potential and time data were digitally converted into dt dE-1, and E was plotted vs. dt dE-1, thus increasing both sensitivity of the method and resolution of the analysis. Quantitative analysis was carried out by the method of standard additions. A good linearity was obtained in the range of concentrations examined. Recoveries of 94-100% for cadmium (II) and of 91-98% for lead (II) were obtained from a sample spiked at different levels. The detection limits were 4.4 ng g-1 for cadmium (II) and 8.6 ng g-1 for lead (II) and the relative standard deviations (mean of nine determinations) were 4.1 and 5.6%, respectively. Results obtained on commercial whole and skim milk were not significantly different from those obtained by inductively coupled plasma atomic emission spectrometry

Determination of zinc (II), cadmium (II), lead (II) and copper (II) in common and balsamic vinegar by stripping chronopotentiometry

A method for the determination of zinc (II), cadmium (II), lead (II) and copper (II) in common and balsamic vinegar by stripping chronopotentiometry is described. The metal ions were concentrated as their amalgams on a glassy carbon working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. Potential and time data were digitally converted into dt dE-1, and E was plotted vs. dt dE-1, thus increasing both sensitivity of the method and resolution of the analysis. Quantitative analysis was carried out by the method of standard additions. A good linearity was obtained in the range of concentrations examined. Recoveries of 90-98% for zinc (II), 91- 97% for cadmium (II), 94-98% for lead (II) and 93-97% for copper (II) were obtained from a sample spiked at different levels. The detection limits were 10.6 ng g-1 for zinc (II), 2.2 ng g-1 for cadmium (II), 3.4 ng g-1 for lead (II) and 4.2 ng g-1 for copper (II) and the relative standard deviations (mean of nine determinations) were 4.8, 6.5, 3.2 and 5.3%, respectively. Results obtained on commercial common and balsamic vinegars were not significantly different from those obtained by atomic absorption spectrometr

Vitamin C inhibits platelet expression of CD40 ligand

Upon stimulation with agonists, platelets express CD40 ligand (CD40L), a transmembrane protein implicated in the initiation and progression of atherosclerotic disease. We have recently discovered that oxidative stress plays a major role in platelet CD40L expression. In this study, we sought to determine whether vitamin C, a known antioxidant, is able to influence platelet CD40L expression. In vitro experiments were done by stimulating platelets with collagen in the presence or absence of vitamin C (50-100 mu M) or vehicle as control. An in vivo study was done in 10 healthy subjects who were randomized to intravenous infusion of placebo or 1 g vitamin C for 45 min in a crossover design. At the end of infusion platelet CD40L and O2- were measured. The in vitro study demonstrated that vitamin C dose dependently inhibited platelet CD40L expression without affecting agonist-induced platelet aggregation. In subjects treated with placebo no changes of platelet CD40L and O2- were observed; conversely, vitamin C infusion caused a significant and parallel decrease of platelet O2- (-70%, P < 0.001) and CD40L (-68%, P < 0.001). Platelet aggregation was not modified by either treatment. This study suggests that water-soluble antioxidants, which scavenge superoxide radicals, may reduce platelet CD40L expression. (c) 2005 Elsevier Inc. All rights reserved