Dijana Jureša

Mercury, arsenic, lead and cadmium in fish and shellfish from the Adriatic Sea

The aim was to measure concentrations of total mercury, total arsenic, lead and cadmium in common edible fresh fish and shellfish from various areas of the Adriatic Sea. Estimates of intake of these elements were made through seafood consumption by the general population. Samples were either wet digested for mercury and arsenic, or dry ashed for lead and cadmium analysis. Mercury was measured by cold vapour atomic absorption spectrometry (CV AAS) and arsenic, lead and cadmium by electrothermal atomic absorption spectrometry (ET AAS). Quality control procedures of analytical methods, which included analyses of dogfish muscle-certified reference material DORM-2, confirmed the acceptability of methods. The highest mercury and arsenic concentrations were found in hake (Merluccius merluccius) and the lowest in mackerel (Scomber scombrus). The respective values in hake were 0.373 ± 0.075 and 23.3 ± 3.6, and in mackerel 0.153 ± 0.028 and 1.06 ± 0.29 mg kg-1 fresh weight (mean ± SD). Lead and cadmium concentrations were about 10 times higher in shellfish than in analysed fish. The highest lead and cadmium concentrations were found in mussel (Mytilus galloprovincialis) and the lowest in hake. Respective lead and cadmium values in mussel were 0.150 ± 0.009 and 0.142 ± 0.017, and in hake were 0.007 ± 0.004 and 0.002 ± 0.001 mg kg-1 fresh weight. The concentrations of analysed elements were below acceptable levels for human consumption set by the Croatian Ministry of Health, except for total arsenic. The estimated intake of those trace elements included in this study through seafood consumption by the general population did not exceed the provisional tolerable weekly intake recommended by the Joint FAO/WHO Expert Committee on Food Additives.

An HPLC/ICPMS study of the stability of selenosugars in human urine: implications for quantification, sample handling, and storage

We report a study with HPLC/ICPMS on the long-term stability of the major selenium metabolite in human urine, namely methyl 2-acetamido-2-deoxy-1-seleno-β-D-galactopyranoside (selenosugar 1). Three separate experiments were performed of 4–28 weeks duration and incorporating various storage conditions: room temperature, 4 °C, −20 °C, −80 °C, lyophilisation, deoxygenation, or addition of a bactericide (NaN3). Triplicate samples of urine or water, spiked with selenosugar 1 at 200 μg Se L−1, were processed in each case. Selenosugar 1 was stable in water under all investigated conditions. For the urine samples, no significant degradation (<2%) was observed after 17 weeks frozen storage at −80 °C, or after lyophilisation and frozen storage at −20 °C, whereas small quantities of degradation products (ca. 3%) were recorded for frozen storage of wet samples at −20 °C. At 4 °C, the selenosugar was essentially unchanged after storage for up to 2 weeks, but clear losses were observed thereafter ranging up to 75% loss after 28 weeks. Several decomposition products were detected by HPLC/ICPMS, one of which was identified as dimethyl diselenide. Although present as only a trace constituent in the urine, dimethyl diselenide was recorded as a large HPLC peak, presumably because of a marked vapour enhancement effect due to more efficient transfer of volatile analytes to the plasma. In addition, total Se analyses revealed that Se was lost from the solutions during storage/handling, presumably as volatile species. Qualitative analysis of volatile species using head space sampling with solid phase microextraction followed by GC/MIP-AES and GC/MS revealed the presence of dimethyl selenide and dimethyl diselenide, based on comparison with standard compounds, and indicated the presence of dimethyl selenylsulfide based on comparison with literature data. The stability of selenosugar 1 and its isomer methyl 2-acetamido-2-deoxy-1-seleno-β-D-glucopyranoside (selenosugar 2), which occurs as a minor species in urine, was also investigated under room temperature storage in the presence and absence of light. Although both species were moderately stable when stored in the dark, their degradation was rapid in the light with clear losses recorded within three days. The work indicates that urine samples should be cooled immediately after collection, and that they may be stored at 4 °C (often the easiest way) for up to 2 weeks before analysis with no appreciable loss of selenosugar. For longer-term storage, urine samples should be kept at −80 °C or, when such facilities are not available, at −20 °C after lyophilisation. The study has also revealed potential quantification problems in Se speciation analysis resulting from different responses for Se species during ICPMS analysis.

HPLC/vapor generation/ICPMS of selenium metabolites relevant to human urine—selective determination of trimethylselenonium ion

Selenium compounds of relevance to investigations into selenium human urinary metabolites, namely three selenosugars, the trimethylselenonium ion (TMSe), and selenomethionine, were examined with respect to their ability to form volatile compounds upon treatment with HCl and NaBH4. All compounds investigated were detectable with HPLC/vapor generation/ICPMS. Under compromise conditions chosen for the simultaneous detection of all five compounds (0.75 M HCl, 1% NaBH4 in 0.1 M NaOH) detection limits (0.09–0.13 μg Se L−1) were in the same range as detection limits obtained by conventional HPLC/ICPMS. Vapor generation of the trimethylselenonium ion was then further investigated, because this selenium compound showed a behavior different from that of the other organic selenium compounds. The detection limit (0.003 μg Se L−1) obtained with a method designed for the selective determination of this compound in human urine was more than one order of magnitude below detection limits usually achieved for selenium compounds with conventional HPLC/ICPMS. Recovery was essentially quantitative (94–99%) when urine spiked with the trimethylselenonium ion at sub μg L−1 concentrations was analyzed. When background urine of a volunteer was analyzed, TMSe was detected at a concentration of 0.10 μg Se L−1. The method allows the determination of the trimethylselenonium ion in urine even if it is only a trace metabolite in the presence of a large excess of selenosugars.

505 Combined early treatment with DMSA and DTPA to mobilize cadmium in rats

The influence of chelating agents: meso-2, 3-dimercaptosuccinic acid (DMSA) ; calcium trisodium diethylenetriaminepentaacetate (DTPA) and their combination on tissue retention and distribution of cadmium (Cd) was compared in female albino rats. Special attention was given to time of chelators application after cadmium administration. After oral cadmium intubation chelators were applied either orally (DMSA) or intraperitoneally (DTPA) in various short time intervals after cadmium. The dose of cadmium chloride was 0, 25 mmol/kg body weight and chelators dose was 1 mmol/kg, each. Three experiments were carried out with four treatment groups in each of them: 1) Cd (control) ; 2) Cd + DMSA ; 3) Cd + DTPA ; 4) Cd + DMSA + DTPA. Time intervals for chelator application after cadmium administration were: immediately in the first, half an hour in the second and one hour in the third experiment. Cadmium, iron, copper and zinc were measured in 24-hour urine collected after chelators application and in organs (liver, kidney and brain) at the end of each experiment. Results showed that the efficiency of cadmium removal from the body is lower when the time of chelator application is longer after cadmium administration. The two chelators differ in efficiency in mobilizing cadmium, with DMSA being more efficient than DTPA. The combined therapies of two chelators give slightly better results of cadmium chelation. It seems that DMSA that is given orally after oral cadmium removes this element very efficiently from the gastrointestinal tract. However, DTPA which is given parenterally removes absorbed cadmium very modestly. Whenever DTPA was given to animals zinc concentration is significantly higher in kidneys and much higher in urine than in other groups. Iron and copper do not change dramatically after chelation treatment.