The determination of polychlorinated biphenyls (PCBs) in water, sediment and fish samples from the Czech Republic was carried out using high resolution gas chromatography with electron capture detection. PCBs concentrations in water and sediment samples were rather low and corresponded with the findings from some prior studies. On the other hand, investigated samples of fish tissue were highly contaminated (on average 1.3-266 ng/g fat for individual PCBs), thus, a continuing contamination of fish species with PCBs was proved.

Veselá H., Šucman E. (2013): Determination of acrylamide in food using adsorption stripping voltammetry. Czech J. Food Sci., 31: 401-406.A new electroanalytical method for the determination of acrylamide in food has been developed. It was found that a complex of acrylamide and Ni 2+ is suitable for the electrochemical determination of acrylamide. Ammonia buffer of pH = 9.5 was found to provide convenient conditions for the determination. Optimal concentration of Ni 2+ was 500 µmol/l. The sample preparation procedure was optimised. The best results were found for an ethanol/water mixture (1:2) and pH = 1.4. The samples were extracted in an ultrasound bath, and after centrifugation 0.2 ml of the extract was taken for the measurement. Voltammetric measurements were done using the hanging mercury drop electrode. The peak height was a function of acrylamide concentration and deposition time. The accuracy of the method was verified by the use of standard reference materials.

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Contamination of ration components and roughage fed to dairy cows and finishing bulls in two different agricultural ecosystems in the district of Uherské Hradi‰tû (localities Buchlovice and Stupava) was monitored. Whereas the site Buchlovice was characterised by intensive agricultural production, the site Stupava was located in the protective zone of the Koryãany water reservoir and ecological agriculture was practised in a part of this area. Materials used for analyses included irrigation water, grass growth, haylage, wheat, roughage, preserved feeds and trough samples of feed. Samples of alfalfa and clover were also collected as ration components and bioindicators of plant origin. From each sample kind and/or sampling site 15 samples were collected. In addition to feeds, bovine milk and beef liver and muscle (m. longissimus dorsi) samples were analysed (10 samples of animal material). Imissions were measured by the mobile laboratory of Regional Hygienic Services, Brno, allowing the determination of SO 2 , NO x , CO, O 3 , fly ash. The samples were analysed for polychlorinated biphenyls (PCB) by high resolution gas chromatography with electron capture detection. Also tested for PCB residues were milk and tissue samples collected from dairy cows and bulls. The concentrations of indicator PCB congeners did not exceed the safety limit in any of the sampling areas (mean concentrations of PCB in feed between 1-2 µg·kg -1 ; mean concentration of PCB and animal tissues between 2-9 µg·kg -1 ). Calculation of the transfer coefficient Q proved to be a suitable tool for the assessment of residue transfer (dairy cows 0.2-1.0; bulls 0.3-1.0). Feed was identified as an important contamination source for animal tissues and milk. Polychlorinated biphenyls, agricultural ecosystem, transfer coefficient Q, food chainsLike other ecosystems, the agricultural ecosystem is exposed to the action of contaminating xenobiotics. In accordance with the world-wide tendencies, criteria for the assessment of the burden by xenobiotics are currently tightened in the Czech Republic to prevent possible damage to human and animal health. Also significant are the effects of pollutants on ecological aspects of the agricultural landscape.In addition to some extrinsic factors of agricultural ecosystems, the transfer of chemical xenobiotics in food chains depends also on intrinsic factors of the agricultural production. The extrinsic factors include the pollution of air, dry and wet imissions, and surface water; the intrinsic factors are associated with biological, physical, chemical and biological characteristics of soil, with the technology of agricultural production, and with zoohygienic conditions. The intrinsic factors become more significant in areas with intensive agricultural production, in which ecological dysbalance of the agricultural ecosystem often develops. Its major cause are high concentration of farm animals, inadequate handling of wastes from animal production, and excessive use of fertilisers. Such activities result in a complex soil...

AbstractŠucman E., Bednář J. (2012): Determination of fluoride in plant material using microwave induced oxygen combustion. Czech J. Food Sci., 30: 438-441.Fluorine is essential in human and/or animal nutrition, thus it is important to know its concentration in a diet. One of the important sources of fluorine for humans is tea, containing relatively high amounts of this trace element. A method for fluoride determination in various kinds of tea using microwave supported sample preparation in a high pressure oxygen atmosphere followed by potentiometry with a fluoride ion-selective electrode were described. The parameters of the microwave device for such combustion procedure were checked and optimised in order to find settings ensuring complete sample combustion and/or absorption of the analyte in the absorption solution. For the ionselective electrode measurement, the technique of standard addition was chosen. The Nernstian slope of the fluoride ion-selective electrode was measured and calculated in the concentration range in which the potential of samples occurred. Concentrations of fluorides in tea in the range from 24.5 mg/kg to 254.5 mg/kg were found. In order to check the accuracy of the method certified reference materials were used. The precision expressed as the relative standard deviation ranged from 3.7% to 15.9%. The method is fast, accurate and reliable for this kind of analysis.