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Hygienická kvalita ryb v 10 údolních nádržích ČR
ŠTEFAN, Daniel
The aim of the theses was to judge the hygienic quality of the most caught and consumed fish species living in 10 Czech water reservoirs according to chosen chemical substances (Hg, Cd, Pb, PCB, DDT, HCH, HCB) in their muscle tissue. The analysed fish were caught between the years 2019 - 2020. The analyses were made by the accredited laboratory of the State Veterinary Institution in Prague. To compare the pollution of individual reservoirs and to compare the results of the monitoring from 2006 - 2010 was as a reference species chosen common bream (Abramis brama). Further, five most frequently caught fish species were taken from each reservoir. The overrun of valid hygienic limit for mercury was found in 15 samples in total out of 6 localities (Lipno, Hněvkovice, Kořensko, Orlík, Skalka and Rozkoš). The highest concentration of mercury (2.948 mg.kg-1) was measured in the mixed sample of muscle tissue of asp fish (Leuciscus aspius) from the Skalka water reservoir. The results of the analysis of other fish muscle tissue from this reservoir proved its continuous strong pollution of mercury. The hygienic limit for the plumb content was overrun in the mixed muscle tissue of common carp (Cyprinus carpio) from Hněvkovice water reservoir in 2019. The repeated analysis in 2020 did not prove an increased contamination of the muscle tissue of the carp from this locality. Other watched pollutants in all samples were below the valid hygienic limit. Statistically important changes of the muscle tissue contamination of common breams by mercury in comparison with the monitoring from the years 2006 - 2010 were found in Lipno, Kořensko, Těrlicko, Žermanice and Skalka localities. However, most of the time there was a connection with different weight of fish used for the analysis. In some localities the increase of PCB was found in comparison with the previous monitoring. The values, however, were deep below the valid hygienic limit. Based on the results of the analysis were also counted recommended numbers of meat portions (170 g) for individual fish species from all localities, possible to be consumed in a month without any health risks. The limiting pollutant in all samples was mercury (or more precisely methylmercury). The results of the thesis proved that the hygienic quality of the fish in all fishing grounds is very good. Certain risk could only be a frequent consumption of predator fish of all sizes. The only exception is the water reservoir Skalka, from which, due to strong contamination with mercury, the consumption of fish cannot be recommended.
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Extraction of Selected Mercury Compounds from Real Samples for Speciation Analysis Employing RP-HPLC-UV-CVG-QTAAS
Kolorosová, Alžběta ; Červený, Václav (advisor) ; Kratzer, Jan (referee)
The extraction of mercury species (methylmercury, ethylmercury, phenylmercury and inorganic mercury(II)) from fish tissue, its determination by reverse phase HPLC, UV-photochemical generation of cold vapour, and detection by atomic absorption spectrometry is described in this work. Various extraction agents and digestion methods were compared in order to find the best alternative. The mixture of 6.25% tetramethylammonium hydroxide and 0.05 mol·l-1 hydrochloride acid was chosen as the best extraction agent. In addition to the high extraction efficiency, the solution involved positively not only UV-photochemical generation, but also separation of observed species. On the contrary, the poor repeatability was achieved with the microwave-assisted digestion due to the proved sorption of mercury species on the Teflon vessels. Therefore, the extraction by high temperature (50-60 řC) in glass bottles was preferred. The results of the determination of the mercury species after the extraction from the real samples were compared to the outcomes obtained by AMA 254. The proposed extraction technique together with the RP-HPLC-UV-CVG-QTAAS is suitable for the speciation analysis of mercury.
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