Pavel Diviš

Application of diffusive gradient in thin films technique (DGT) to measurement of mercury in aquatic systems

The diffusive gradient in thin films (DGT) technique was investigated and used to measure mercury concentration in river water. Mercury ions are covalently bound to amide nitrogen groups of commonly used polyacrylamide, which makes this gel unsuitable as a diffusive medium. In contrast, agarose gel was found as the diffusive gel for mercury measurements. Basic performance tests of agarose DGT verified the applicability of Ficks first law for DGT measurements. Two selective resins, Chelex-100 with iminodiacetic groups and Spheron-Thiol with thiol groups were used. The measured diffusion coefficient in agarose gel was close to that in water. The concentration of mercury in Svitava river measured by DGT with Speron-Thiol resin gel was higher (0.0116 +/- 0.0009mugl(-1)) than those obtained by Chelex-100 (0.0042 +/- 0.0005mugl(-1)). Different capture efficiencies of two adsorbents enable to estimate fractions of mercury bonded in different complexes in the river water. The concentrations of mercury found by DGT both Chelex-100 and Speron-Thiol resin gels are much lower than that measured directly in the river water (0.088 +/- 0.012mugl(-1)). This difference indicates that DGT concerns inorganic ions and labile species only, and that it is not able to include inert organic species and colloids.

Determination of trace amounts of total dissolved cationic aluminium species in environmental samples by solid phase extraction using nanometer-sized titanium dioxide and atomic spectrometry techniques

Nanometer-sized titanium dioxide was used as a solid-phase extractant for the separation and preconcentration of trace amounts of Al(III) prior to its determination by electrothermal atomic absorption spectrometry (ET AAS) and inductively coupled plasma optical emission spectrometry (ICP OES). The optimal conditions for the proposed solid phase extraction (SPE; 50mg TiO(2), 10 min extraction time, pH 6.0, HCl and HNO(3) as eluents) and ET AAS measurement (1500 degrees C pyrolysis and 2600 degrees C atomization temperatures, Mg(NO(3))(2) as matrix modifier) were obtained. The adsorption capacity of TiO(2) was 4.1mg Al g(-1) TiO(2). Two modes of the proposed procedure were compared, (I) batch and elution mode with the elution of Al from TiO(2) phase by nitric or hydrochloric acid, and (II) batch and slurry mode (without elution) with the direct TiO(2) phase-slurry sampling. Finally, the batch and slurry mode of nanometer-sized TiO(2) SPE with slurry ET AAS detection and quantification was preferred and used for the determination of trace amounts of total dissolved cationic Al species in synthetic and natural water samples. The method accuracy was checked by the analysis of lake water CRM TMDA-61 and by the technique of analyte addition (sample spiking). Under the optimal conditions, the calibration curve for batch and slurry TiO(2) SPE with a 10-fold preconcentration was linear up to 40 microg L(-1) Al. The limit of detection (LOD) and the limit of quantification (LOQ) was 0.11 microg L(-1) Al and 0.35 microg L(-1) Al, respectively, with a preconcentration factor of 20 and a relative standard deviation (RSD) lower than 5%.

Evaluation of Various Inorganic and Biological Extraction Techniques Suitability for Soil Mercury Phytoavailable Fraction Assessment

This article evaluates various extraction techniques’ suitability for soil mercury phytoavailable fraction assessment, including DGT method and extraction with microscopic filamentous fungi metabolites, MgCl2, rainwater, and EDTA. After mercury extraction from contaminated soils by these techniques, the obtained data were compared to mercury accumulation by shoots of barley (Hordeum vulgare L.). Comparison of these values showed that DGT method is able to separate soil mercury with the best agreement to total mercury concentration in shoots of barley. However, comparing mercury extraction efficiency of selected techniques to extraction efficiency of barley, statistical significance at 0.05 significance level was proved for fungal Cladosporium sp. and Alternaria alternata metabolites. Our results indicate that these extraction techniques are suitable for risk assessment of mercury phytoavailability in contaminated areas.

Characterization of sorption gels used for determination of mercury in aquatic environment by diffusive gradients in thin films technique.

AbstractThe influence of pH, ionic strength and selected natural ligands on the measurement of mercury by the diffusive gradients in thin films technique (DGT) using recently introduced sorption gels was determined. Sorption gels containing Chelex 100, Spheron-Thiol, Duolite GT73 and modified Iontosorb AV resins were investigated, with the sorption capacity determined for all used sorption gels. The minimum DGT measurable concentrations were calculated from 3 times the standard deviation of mercury amount in unexposed sorption gels.

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.

The effect of hydroxyapatite particle size on viscoelastic properties and calcium release from a thermosensitive triblock copolymer

Well-defined “smart” injectable hydrogel based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(lactic acid-co-glycolic acid) (PLA/PGA) copolymer (PLGA-PEG-PLGA) gelling at the body temperature was modified by bioactive hydroxyapatite (HAp) in the form of micro-, nano-, and core-shell particles (μ-HAp, n-HAp, and CS-x, respectively) to be applicable as calcium delivery system in bone regeneration. Viscoelastic moduli increased with HAp content as expected. Whereas systems containing μ-HAp or CS-x particles maintained two sol-gel and gel-sol phase transitions, the n-HAp containing system showed only one sol-gel phase transition due to the strong interactions between polymer chain and the n-HAp surface. In vitro, studies proved the controlled uniform release of calcium cations from both CS-x and n-HAp over the 9-day period without any initial burst release.

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).