Ingvar A. Bergdahl

Fractionation of soluble selenium compounds from fish using size-exclusion chromatography with on-line detection by inductively coupled plasma mass spectrometry

Fish accumulate significant amounts of selenium and are an important dietary source of this element. Some studies have however indicated a low bioavailability of the selenium from fish. Since little is known of the selenium forms in fish, we have studied soluble selenium compounds in fish species, and compared different techniques for fractionation of selenocompounds (size-exclusion chromatography, ultrafiltration, and precipitation with trichloroacetic acid). The size-exclusion column (Superdex 200 HR 10/30) was coupled on-line to inductively coupled plasma mass spectrometry (ICP-MS). The limit of detection was 0.20 µg l–1 and the selenium response was linear in the investigated concentration range of 0–20 µg l–1 (r2 = 0.98). For plaice 47% of the selenium was extractable while the extraction efficiency for cod was 23%. The fish extracts were injected onto the column four times each and the variation in the quantitative data for different selenium-containing fractions between the runs was small (RSD <10%). The recovery of selenium in the chromatographic step was about 70%, indicating some interaction between the fish extracts and the column material. Ultrafiltration using a membrane with a cut-off at Mr 10000 gave results similar to the size-exclusion fractionation, for cod about 20% of the soluble selenium had a Mr < 10000 and the corresponding value for plaice was 69%. Removal of high-molecular-weight compounds from the sample by trichloroacetic acid precipitation showed a similar proportion of low-molecular-weight compounds for plaice (77%), while the obtained value for cod was higher (38%) compared with the other techniques.

Chapter 43 – Lead

Inorganic lead is the most extensively studied toxic agent. In addition to occupational exposure, there is widespread exposure in the general environment, although this has decreased dramatically after the ban of lead addition to gasoline. Toxic effects may occur in both the central and peripheral nervous systems; the blood (including inhibition of heme synthesis, which also affects all other cells); the kidney; the cardiovascular, endocrine, and immune systems; the gastrointestinal tract; and female and male reproduction. Lead passes into the placenta. Slight (but adverse) effects on the mental development of infants and children have repeatedly been reported at a mean blood lead concentration (B-Pb) of ≤xa00.25xa0μmol/L, without obvious threshold. Lead causes an increase in blood pressure at a mean B-Pb of ≤xa00.5xa0μmol/L. Lead is carcinogenic in animal experiments, but there is only limited evidence for carcinogenicity in humans. n nThe organolead compounds tetraethyl- and tetramethyllead, earlier used in enormous quantities in leaded gasoline, are easily absorbed through inhalation and through the skin, and may cause acute encephalopathia.