Jaromír Pořízka

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.

Multi-experimental characterization of selected medical plants growing in the Czech Republic

Complex analysis of the impact of post-production conditions on antioxidant status, content of selected polyphenols, color, and concentration of selected metals was evaluated in the group of ten most popular medical plants conventionally produced in the Czech Republic. Ultraviolet visible near infrared spectroscopy (UV–VIS–NIR), electron paramagnetic resonance (EPR), high-performance liquid chromatography (HPLC), and inductively coupled plasma optical emission spectrometry (ICP-OES) were employed for these purposes. The entire data set of the obtained experimental characteristics was processed by multivariate statistical methods to assess the influence of the way of processing on sample properties. On the basis of 11 characteristics identified by the analysis of variance (ANOVA) as the most significantly different, successful differentiation of medical plant samples was achieved according to post-harvest treatment, families, and individual medical plant species by means of canonical discrimination method, reaching 100, 89.5, and 100% correctness, respectively. The importance of the sample processing on their properties and on the concentration of target naturally containing compounds with health-promoting and antioxidant properties was thus proved unambiguously.

Influence of Pb Dosage on Immobilization Characteristics of Different Types of Alkali-Activated Mixtures and Mortars

Alkali-activated matrices are suitable materials for the immobilization of hazardous materials such as heavy metals. This paper is focused on the comparison of immobilization characteristics of various inorganic composite materials based on blast furnace slag and on the influence of various dosages of the heavy metal Pb on the mechanical properties and fixation ability of prepared matrices. Blast furnace slag (BFS), fly ash, and standard sand were used as raw materials, and sodium water glass was used as an alkaline activator. Pb(NO3)2 served as a source of heavy metal and was added in various dosages in solid state or as aqueous solution. The immobilization characteristics were determined by leaching tests, and the content of Pb in the eluate was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). The microstructure of matrices and distribution of Pb within the matrix were determined by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Increasing the dosage of the heavy metal had negative impacts on the mechanical properties of prepared matrices. The leaching tests confirmed the ability of alkali-activated materials to immobilize heavy metals. With increasing addition of Pb, its content in eluates increased.

Silver Nanoparticles Production with Probiotic Bacteria

Silver nanoparticles (colloidal silver) have a bactericidal effect against a variety of bacteria, fungi and viruses. They are promising for biomedical applications due to the limited toxicity against eukaryotic cells. Important role in the silver nanoparticles production have various microorganisms including lactic acid bacteria of the genus Lactobacillus. Probiotic Lactobacillus species are good candidates for nanoparticles producing in the laboratory and in industrial scale, too. The aim of this work was to test the production of colloidal silver nanoparticles with probiotic species Lactobacillus casei. Nanoparticles production was tested in the reaction mixtures (phosphate buffer, glucose, bacterial cells) upon addition of varying concentrations of AgNO3 (1 - 4mM). Production of the silver nanoparticles was proven by screening of reaction mixtures by Transmission electron microscopy. Level of Ag+ ions utilization to nanoparticles was analysed by optical emission spectrometry. Results showed high efficiency of nanosilver production with narrow size distribution of nanoparticles (12 - 27nm).