P. Brätter

Maternal selenium status influences the concentration and binding pattern of zinc in human milk.

To study the health effects of high dietary maternal selenium intake breast milk, blood and toe-nails were collected from 143 women (20-24 days of lactation) living in Venezuelan states of Yaracuy and Portuguesa. Depending on the regional selenium intake level three regions were defined within the total range of 90-980 microgram per day. The samples were analyzed by means of INAA for the determination of trace elements, including selenium and zinc. The significant inverse correlation between Se and Zn in breast milk found in former studies was confirmed. Investigation of the Zn-binding pattern in milk whey was carried out by an on-line combination HPLC (SEC) for protein separation and ICP-AES for element detection. Six Zn-binding compounds including citrate were detected. A highly significant negative correlation was found between the citrate, which is the main low-molecular Zn-binding compound, and the maternal daily selenium intake. We determined that the decrease in zinc concentration is due to a decrease in the citrate level, which depends on the selenium concentration in breast milk. The selenium concentration in breast milk is, in turn, proportional to the dietary intake. In addition, significant changes in the UV- and Zn-profiles were observed in the milk whey with the highest selenium content, indicating that above a certain maternal intake level substantial changes in the composition of mammary secretory cells occur. This effect can be of interest for estimation of the safe dietary intake level of selenium.

The TSH-dependent variation of the essential elements iodine, selenium and zinc within human thyroid tissues.

Instrumental Neutron Activation Analysis was used in order to measure iodine, selenium and zinc concentration in thyroid samples. A pair of samples of normal and nodular tissue were collected from the thyroid gland from 72 patients selected on the basis of pathological criteria (44 cases of multinodular goiter, 12 of chronic lymphocytic thyroiditis (CLT), 6 of thyroid adenoma (TA) and 12 of thyroid cancer (TC)). The check for tissue homogeneity and sampling error was performed by means of the coefficient of variation (CV%) of the elements in replicate samples of normal and altered tissues. High CV% values (> 15%) for iodine reflected a functional variability in thyroid follicles, while low CV% values (< 10%) for selenium and zinc indicated that the composition of selected tissues was rather homogeneous. The variation of the elements concentration was compared in normal and altered tissues. The mean element concentrations had values close to those already reported in the literature; furthermore, our patients had marginal iodine and selenium deficiency. Both normal and nodular tissues in CLT showed statistically significant lower zinc values as compared with the other thyroid diseases. To evaluate the thyroid function, thyroid stimulating hormone (TSH) and thyroxine (T4) levels were measured in the serum of patients. Two arbitrary serum-TSH threshold levels (TSH < 1.0 and > 4.0 mU/L) were introduced in order to classify, respectively, hyperthyroidism and hypothyroidism, as well as euthyroid conditions (1.0 < TSH < 4.0 mU/L), and each patient was assigned to one of these groups. The influence of TSH in the variation of the concentration of iodine, selenium and zinc in normal and altered human thyroid tissues was significant.

Determination of mineral and trace elements in total diet by inductively coupled plasma atomic emission spectrometry: comparison of microwave-based digestion and pressurized ashing systems using different acid mixtures

The effectiveness of different acid mixtures for the de-mineralization of total diet samples of different origin and composition by means of a closed microwave-based technique and a pressurized-ashing technique were investigated. The aim was to obtain complete acid solubilization for the subsequent accurate determination of Al, Ca, Cu, Fe, K, Mg, Na, P and Zn by means of inductively coupled plasma atomic emission spectrometry (ICP-AES). The sampling and sample preparation steps for the trace element analysis are described. The special care taken in the sampling design to ensure the representativeness of the sample for the population studied is also mentioned. The regions and population groups were selected from the high mountain valleys, where a high incidence of stomach cancer exists, and a low altitude valley at the foot of the Andes, which is a low stomach cancer incidence region, both located in the state of Tachira, Venezuela. Total diets including breakfast, lunch, supper, snacks and drinks from the whole-day intake of 140 adults were collected. The collection of the total diet was made according to the double-portion technique. The most reliable digestion procedure for the determination of Al, Ca, Cu, Fe, K, Mg, Na, P and Zn in total diet by means of ICP-AES was a microwave-based technique using HNO3 alone or with the mixture HNO3+ H2O2(2 + 1). In comparison, a pressurized-ashing technique is faster although lower values for K (13 and 11%) were obtained. Despite low sensitivity for the ICP-AES measurements, the microwave-based digestion using HNO3+ H2SO4(4 + 1) also gave good agreement for the determination of Al, Ca, Cu, Fe, K, Mg, Na, P and Zn by means of ICP-AES. Because of the simple and rapid procedure, the pressurized-ashing technique using the mixture HNO3+ H2O2(2 + 1) was selected to perform the digestion of the total diet samples collected. The results of the mean daily intake of the population investigated showed for the high mountain valleys (high stomach cancer incidence area, n= 77) as compared with the low altitude valleys (low stomach cancer incidence area, n= 33) significantly higher daily intake with respect to Na (2082 versus 1471 mg), K (1190 versus 731 mg), P (640 versus 381 mg) and a significantly lower daily intake with respect to Ca (925 versus 1379 mg) and Cu (2.78 versus 4.66 mg). No differences were obtained with respect to Al, Fe, Mg and Zn.

Determination of aluminium in infusion solutions by inductively coupled plasma atomic emission spectrometry—a critical comparison of different emission lines

Seven emission lines for the determination of Al in infusion solutions by means of inductively coupled plasma atomic emission spectrometry were compared. For this comparison, wavelength scans of different samples were made in order to study the background in the region of each line and to inspect for interference structures arising from molecular bands of water and argon. Background equivalent concentrations and detection limits were calculated for the emission lines at 167, 237, 394 and 396 nm. The detection limits were 1.2 µg l–1 for the 167 nm line, 8.8 µg l–1 for the 237 nm line, 10 µg l–1 for the 394 nm line, 4.7 µg l–1 for the 396 nm line and > 10 µg l–1 for the other three lines (226, 308 and 309 nm). The Al content of various infusion solutions was determined on different days using the three emission lines with the lowest detection limits (167, 237 and 396 nm). Day-to-day-variation was approximately 5% in all cases. As a final step, the Al contamination of 25 infusion solutions for parenteral nutrition was evaluated by using the two most suitable emission lines (167 and 396 nm). No statistically significant differences between the results were detected. Advantages and disadvantages of these two emission lines for the determination of Al are discussed.

[Determination of minerals and trace elements in selenium tea from the Enschi district, People's Republic of China, and in its infusions using inductively coupled plasma-atomic emission spectrometry, graphite furnace atomic absorption spectrometry and instrumental neutron activation analysis].

The Enschi district in Hubei province, Peoples Republic of China is geochemically one of the two seleniferous regions, producing both selenium (Se) black tea and the Se green tea. Three samples of green tea with different Se contents and one non-Se tea were analysed. The following mineral and trace elements were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES): K, Ca, Mg, Na, P, S, Al, Mn, Fe, Ba, Sr, Co, Ni, Cu, Zn, Mo, and Cr. Except for Mo, Co, and Cr, all other elements in infusions of the samples analysed were also measured, since their concentrations are lying over their detection limits. The Se content in the tea samples and in the infusions were measured with graphite furnace atomic absorption spectrometry (GFAAS). The accuracy of Se determination was tested by measuring untreated tea samples with instrumental neutron activation analysis (INAA). The Se content in the measured samples was 1 to 8.5 μg/g. In addition to Se, 17 other elements were measured in the tea samples and 14 others in the infusions. With this data the extractible part of this elements in the infusion were calculated. Up to 10% of the Se was found in a first infusion.ZusammenfassungDas Enschi-Gebiet in der Provinz Hubei ist geochemisch eine der beiden selenreichen Regionen Chinas. Hier werden die grünen und schwarzen Selen-Tees produziert. Drei Proben eines grünen Tees mit verschieden hohen Se-Gehalten sowie eine selenarme Probe wurden in dieser Arbeit untersucht. Die Mineralstoffe und Spurenelemente K, Ca, Mg, Na, P, S, Al, Mn, Fe, Ba, Sr, Co, Ni, Cu, Zn, Mo und Cr wurden mittels Atomemissionsspektrometrie mit induktiv gekoppelter Plasmaanregung (ICP-AES) bestimmt. Außer Mo, Co und Cr wurden alle oben genannten Elemente in den Aufgüssen der untersuchten Selen-Tees ebenfalls mit der ICP-AES gemessen. Die Se-Gehalte in den Teeproben sowie in den Aufgüssen wurden mit Graphitrohr-Atomabsorptionsspektrometrie (GFAAS) bestimmt. Zur Kontrolle der Richtigkeit der Se-Messung wurden die Se-Gehalte in unaufgeschlossenen Teeproben zusätzlich mit instrumenteller Neutronenaktivierungsanalyse (INAA) bestimmt. Es wurden Se-Gehalte im Bereich von 1 bis 8,5 μg/g Trockengewicht gemessen. Außer Se wurden insgesamt 17 Elemente im Tee und 14 in dessen Aufguß quantitativ bestimmt. Daraus wurde der Auslaugungsgrad für die einzelnen Elemente berechnet. Bis zu 10% des Se konnten in einem ersten Aufguß ausgelaugt werden.