Determination of tin, chromium, cadmium and lead in canned fruits from the Czech market

The global production of metal cans is more than 300 billion cans. Benefits of metal packaging consist mainly from the great strenght, excellent barrier properties and good thermal conductivity. The main problem of used metal packaging are the corrosion processes. The corrosion of metal container causes dissolution of tin which is used as a protective layer of the steel shell of the can and other metallic elements used in the manufacture of cans. In this work 31 samples of canned fruit was analysed and the concentration of tin, chromium, cadmium and lead was determined in fruit and in syrup using ICP-OES and ICP-MS techniques. The results showed no difference between the concentration of analysed elements in fruit and in syrup. In none of the analyzed samples the permitted maximum concentration of tin 200 mg.kg-1 was exceeded. Maximum concentration of tin was measured in canned grepfruit (59.8 ±1.9 mg.kg-1). The age of cans had no significant effect on the concentration of tin in canned fruit. The concentration of tin in fruit packaged in cans with protective layer of lacquer was significantly lower than the concentration of tin in fruit packaged in cans without protective layer of lacquer. Concentration of chromium, cadmium and lead in the analysed samples was very low at the natural levels of occurrence of these metals in fruit and it was impossible to determine unequivocally that the measured concentrations of these metals in canned fruit originate from the corrosion of can. The corrosion of the tinplate was studied using scanning electron microscopy with an energy dispersive spectrometer. By analyzing the SEM pictures and EDS spectra, critical areas of tin plate corrosion were observed. Based on the measured results it can be concluded that the consumption of fresh canned fruit is not a major problem for the inhabitants of the Czech Republic in terms of intake of potentially hazardous metals

Propsective surface treatments of magnesium alloys

Cieľom tejto bakalárskej práce je zhrnutie poznatkov o metódach povrchových úprav na horčíkových zliatinách a preskúmanie ich efektívnosti voči korózii. Horčík na rozdiel od iných technicky využívaných kovov má najmenšiu odolnosť voči korózii, ktorá sa zvyšuje legovaním, alebo povrchovými úpravami. V úvodnej časti sú zhrnuté všeobecné poznatky o horčíku, jeho zliatinách AZ31, AZ91 a korózii. Rešeršná časť zahŕňa doterajšie výsledky výskumu ohľadom týchto zliatin, pričom dôraz je kladený na fluoridové konverzné povlaky a kompozitné povlaky na báze niklu, kde popisujeme ich prípravu a pozornosť sústreďujeme na ich ochranné vlastnosti pred koróznym napadnutím. Výstupom práce je kritické zhodnotenie pozitív a negatív protikoróznych ochranných vrstiev na Mg zliatinách a návrh vhodných experimentov k overeniu reprodukovateľnosti výsledkov publikovaných v literatúre.The aim of this bachelor thesis is to summarize the methods of surface treatment of magnesium alloys and discussion of theireffectiveness of corrosion protection. In contrast to other metallic material used in technical practice, magnesium alloys have the lowest corrosion resistance, which can be increased by alloying or by use of surface treatments. The introduction part of the thesis deals with general knowledge about magnesium, its alloys AZ31, AZ91 and their corrosion processes. The recherché includes actual results of research about these alloys. Emphasizedare fluoride conversion coatings and composite coatings based on nickel, where their preparation is described and attention is focused on their properties in the sense of corrosion protection. Concluding the work, we give a critical assessment of the pros and cons of corrosion protective coatings on Mg alloys. Finally, there are suggested some convenient experiments to prove the repeatability of results published in the recherché literature.

Fluoride coatings on magnesium prepared in melts

Táto práca sa zaoberá protikoróznou ochranou horčíkových zliatin AZ31, AZ61, AZ91 pomocou fluoridového konverzného povlaku pripraveného z taveniny Na[BF4]. V teoretickej časti sú popísané vlastnosti horčíkových zliatin, súčasné výsledky príprav fluoridových konverzných povlakov a rozbor dostupnej literatúry ohľadom vlastnosti soli Na[BF4] a jeho produktov rozkladu. Experimentálna časť bola rozdelená na dve hlavné časti. Prvá sa zaoberá koróznou odolnosťou ošetrených horčíkových zliatin (AZ31, AZ61, AZ91 a žíhanej AZ91) v tavenine Na[BF4]. Korózna odolnosť bola testovaná pomocou potenciodynamických skúšok a skúšok v koróznej komore. V druhej časti bol skúmaný mechanizmus prípravy fluoridového konverzného povlaku, pričom bolo preukázané, že bez prístupu vzduchu ako oxidačné činidlo v procese vystupuje bór, ktorý sa redukuje z BIII na B0, a tým umožňuje vznik fluoridového konverzného povlaku.This work deals with the corrosion protection of magnesium alloy AZ31, AZ61, AZ91 using fluoride conversion coating prepared from Na[BF4] melt. The theoretical part describes the properties of magnesium alloys, the recent results of fluoride conversion coatings preparation and analysis of the available literature about the properties of salt Na[BF4] and its decomposition products. The experimental part was devided into two main sections. The first deals with the corrosion resistance of the treated magnesium alloys (AZ31, AZ61, AZ91 and AZ91 annealed) in the Na[BF4] melt. Corrosion resistance was tested using potentiodynamic tests and tests in the corrosion chamber. In the second part, the mechanism has been studied for preparing fluoride conversion coating, where it was shown that in air-free atmosphere the oxidizing agent in the process is boron, which is reduced from BIII to B0, and thereby enables the fluoride conversion coating.

Vertebral column adaptations in juvenile Atlantic salmon Salmo salar, L. as a response to dietary phosphorus

Deficiency in dietary phosphorus (P) is considered as a nutritional risk factor for the development of vertebral column deformities in farmed Atlantic salmon Salmo salar, L. This mono-factorial study examines how 11-week deficiency and excess of dietary P influence the structure and microstructure of the vertebral bodies in juvenile, freshwater stages of Atlantic salmon. Animals were fed continuously with three diets containing different levels of total P (tP) and soluble P (sP), respectively: low P (LP) = 6.8 g/kg tP, 3.5 g/kg sP, regular P (RP) = 10.0 g/kg tP, 5.6 g/kg sP, and high P (HP) = 13.0 g/kg tP, 9.3 g/kg sP. Animals were analysed for plasma and bone mineral content, vertebral column deformities (x-ray), vertebral centra stiffness, bone mineralisation pattern and vertebral body microanatomy (cells and connective tissue structures). A low (background) level of deformities was observed on a gross morphological level but no increase and no specific type of vertebral column deformity was associated with either of the three groups. While feed intake was comparable among all diet groups animals fed LP showed a 50% reduction in total calcium (Ca) and P content in abdominal vertebrae and opercula. Regular P and HP animals showed similar levels of total Ca and P in abdominal vertebrae and opercula. Animals in all diet groups showed well-developed vertebral bodies. Low P animals had vertebral centra, neural and haemal arches with large areas of non-mineralised bone. Vertebral centra stiffness in LP animals was reduced accordingly. Regular P and HP animals showed comparable values for vertebral centra stiffness. Non-mineralised vertebral body end plates of LP animals developed a slight inward bending and intervertebral ligaments increased in length and thickness. The cellular and extracellular components of the intervertebral joints remained intact without structural alterations that would indicate the development of vertebral centra compression or fusion. Animals from all three diet groups showed active osteoblasts at the vertebral body growth zone. Despite the three-fold decline in plasma inorganic P in LP animals growth continued at the same rate as in RP and HP animals. It is discussed whether the use of a P-reduced diet under a continuous feeding regime can maintain growth without adverse effects for animal health and welfare. This study further discusses that a HP diet relative to an RP diet has no beneficial effect concerning bone formation, bone mineralisation, growth and prevention of vertebral centra deformities in Atlantic salmon parr.publishedVersio

Influence of the Composition of the Hank’s Balanced Salt Solution on the Corrosion Behavior of AZ31 and AZ61 Magnesium Alloys

namic tests and electrochemical impedance spectroscopy. The influence of the solution composition and material surface finish was examined also through the analysis of corrosion products created on the samples’ surface after electrochemical measurements in terms of scanning electron microscopy using energy-dispersive spectroscopy. Obtained data revealed the differences in the response of the magnesium alloys to enriched Hank’s Balanced Salt Solution—HBSS+ (with Mg2+ and Ca2+ ions) and Hank’s Balanced Salt Solution—HBSS (without Mg2+ and Ca2+ ions). Both examined alloys exhibited better corrosion resistance from the thermodynamic and kinetic point of view in the enriched HBSS+. AZ61 magnesium alloy reached higher values of polarization resistance than AZ31 magnesium alloy in both the used corrosion solutions. Phosphate-based corrosion products were characteristic for the AZ31 and AZ61 alloys tested in the HBSS (without Mg2+ and Ca2+ ions). The combination of phosphate-based corrosion products and clusters of MgO and Mg(OH)2 was typical for the surface of samples tested in the enriched HBSS+ (with Mg2+ and Ca2+ ions). Pitting corrosion attack was observed only in the case of enriched HBSS+

Modulation of metabolic activity of phagocytes by antihistamines

The purpose of the study was to investigate the effects of H1-antihistamines of the 1st generation (antazoline, bromadryl, brompheniramine, dithiaden, cyclizine, chlorcyclizine, chlorpheniramine, clemastine) and the 2nd generation (acrivastine, ketotifen, and loratadine) on the respiratory burst of phagocytes. Reactive oxygen species generation in neutrophils isolated from rat blood was measured using luminol-enhanced chemiluminescence. Changes in nitrite formation and iNOS protein expression by RAW 264.7 macrophages were analysed using Griess reaction and Western blotting. The antioxidative properties of drugs in cell-free systems were detected spectrophotometrically, luminometrically, fluorimetrically, and amperometrically. The majority of the H1-antihistamines tested (bromadryl, brompheniramine, chlorcyclizine, chlorpheniramine, clemastine, dithiaden, and ketotifen) exhibited a significant inhibitory effect on the chemiluminescence activity of phagocytes. H1-antihistamines did not show significant scavenging properties against superoxide anion and hydroxyl radical, thus this could not contribute to the inhibition of chemiluminescence. H1-antihistamines had a different ability to modulate nitric oxide production by LPS-stimulated macrophages. Bromadryl, clemastine, and dithiaden were the most effective since they inhibited iNOS expression, which was followed by a significant reduction in nitrite levels. H1-antihistamines had no scavenging activity against nitric oxide. It can be concluded that the effects observed in the H1-antihistamines tested are not mediated exclusively via H1-receptor pathway or by direct antioxidative properties. Based on our results, antihistamines not interfering with the microbicidal mechanisms of leukocytes (antazoline, acrivastine and cyclizine) could be used preferentially in infections. Other antihistamines should be used, under pathological conditions accompanied by the overproduction of reactive oxygen species

PEO of AZ31 Mg Alloy: Effect of Electrolyte Phosphate Content and Current Density

In this work, the quality of coatings prepared by plasma electrolytic oxidation (PEO) on an AZ31 magnesium alloy were evaluated. This was done by studying the effects of the chemical composition of phosphate-based process electrolytes in combination with different applied current densities on coating thickness, porosity, micro-cracking and corrosion resistance in 0.1 M NaCl. Both processing parameters were studied in four different levels. Mid-term corrosion resistance in 0.1 M NaCl was examined by electrochemical impedance spectroscopy and based on this, corrosion mechanisms were hypothesized. Results of performed experiments showed that the chosen processing parameters and electrolyte composition significantly influenced the morphology and corrosion performance of the prepared PEO coatings. The PEO coating prepared in an electrolyte with 12 g/L Na3PO4 center dot 12H(2)O and using an applied current density 0.05 A/cm(2) reached the highest value of polarization resistance. This was more than 11 times higher when compared to the uncoated counterpart

Chemiluminescence response induced by mesenteric ischaemia/reperfusion: effect of antioxidative compounds ex vivo

Ischaemia and reperfusion (I/R) play an important role in human pathophysiology as they occur in many clinical conditions and are associated with high morbidity and mortality. Interruption of blood supply rapidly damages metabolically active tissues. Restoration of blood flow after a period of ischaemia may further worsen cell injury due to an increased formation of free radicals. The aim of our work was to assess macroscopically the extent of intestinal pathological changes caused by mesenteric I/R, and to study free radical production by luminol enhanced chemiluminescence (CL) of ileal samples. In further experiments, the antioxidative activity of the drugs tested was evaluated spectrophotometrically by the use of the DPPH radical. We studied the potential protective ex vivo effect of the plant origin compound arbutin as well as of the pyridoindole stobadine and its derivative SMe1EC2. I/R induced pronounced haemorrhagic intestinal injury accompanied by increase of myeloperoxidase (MPO) and N-acetyl-β-D-glucosaminidase (NAGA) activity. Compared to sham operated (control) rats, there was only a slight increase of CL response after I/R, probably in association with neutrophil increase, indicated by enhanced MPO activity. All compounds significantly reduced the peak values of CL responses of the ileal samples ex vivo, thus reducing the I/R induced increase of free radical production. The antioxidants studied showed a similar inhibitory effect on the CL response influenced by mesenteric I/R. If proved in vivo, these compounds would represent potentially useful therapeutic antioxidants

Effects of reactive oxygen species and neutrophils on endothelium-dependent relaxation of rat thoracic aorta

Reactive oxygen species (ROS) are produced in different metabolic processes including the respiratory burst of neutrophils accompanying local inflammation. The aim of this study was to analyze the effects of N-formyl-methionyl-leucyl-phenylalanine (FMLP)-activated neutrophils, isolated from the guinea pig peritoneal cavity, on isolated rings of a large (conduit) artery, the rat thoracic aorta. FMLP-activated neutrophils enhanced the basal tension increased by α1-adrenergic stimulation. In phenylephrine-precontracted aortae, they elicited marked contraction, while in noradrenaline-precontracted rat aortal rings they caused a biphasic response (contraction-relaxation). To eliminate interaction of activated neutrophils with catecholamines, in the subsequent experiments the basal tension was increased by KCl-induced depolarization. Activated neutrophils evoked a low-amplitude biphasic response (relaxation-contraction) on the KCl-induced contraction. Not only the acetylcholine- and A23187-induced relaxations but also the catalase sensitive hydrogen peroxide (H2O2) elicited contractions were endothelium-dependent. Even though the acetylcholine-induced relaxation was changed by activated neutrophils and by the ROS studied, their effects differed significantly, yet none of them did eliminate fully the endothelium-dependent acetylcholine relaxation. The effect of activated neutrophils resembled the effect of superoxide anion radical (O2 •–) produced by xanthine/xanthine oxidase (X/XO) and differed from the inhibitory effects of Fe2SO4/H2O2-produced hydroxyl radical (•OH) and H2O2. Thus O2 •– produced either by activated neutrophils or X/XO affected much less the endothelium-dependent acetylcholine-activated relaxation mechanisms than did •OH and H2O2. In the large (conduit) artery, the effects of activated neutrophils and various ROS (O2 •–, •OH and H2O2) seem to be more dependent on muscle tension than on endothelial mechanisms