L. Balint

Estimation of dietary intake of lead and cadmium in the general population of the Republic of Croatia

The level of lead and cadmium in foodstuffs in the Republic of Croatia was determined by the method of atomic absorption spectrophotometry from the beginning of 1988 to mid 1993. Mean weekly dietary intake of these toxic metals was then estimated on the basis of the level of contamination and consumption of the foodstuffs concerned. The results show that mean weekly dietary intake of lead is 701 micrograms/person and 121.4 micrograms cadmium/person. With respect to the provisional tolerable weekly intake (PTWI), these values are equal to 19.9% for lead and 24.4% for cadmium.

Spectrofluorometric method for determination of the total mercury content in environmental samples — Waste waters

A highly selective spectrofluorometric method for the determination of total mercury (Hg) in waste waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, is the basis of this sensitive method. All forms of mercury, including organic compounds, are pre-oxidized to ionic mercury by acidic potassium permanganate. The final and complete oxidation is achieved by adding potassium persulphate and heating. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. The recoveries were done by adding 3.0 μg Hg/100 ml to each sample before the digestion. It was indicated that the recoveries for determining mercury in waste waters were 98.3%–102.7%. The method gives reliable results down to a concentration of 10 ng Hg/ml waste water.

Dynamics of the accumulation of thiamine during maturation of soybean seeds

Summary The dynamics of the accumulation of thiamine were followed in developing seeds of four genotypes of soybean under defined climatic and constant topographical and agrotechnical conditions in the course of three consecutive vegetation years. Tests were carried out at weekly intervals until the seeds were completely mature and had a moisture content of about 14%. Thiamine content was determined fluorometrically by measuring the intensity of thiocrome fluorescence. It was found that the greatest accumulation of the dry matter took place during the seed development stages III and IV whereas thiamine accumulation is more or less linear during the development. Maximal concentrations of thiamine were found in mature seeds. Although the dynamics of accumulation, regardless of the year of investigation, were the same in all the genotypes, the analysis of the impact of climatic factors showed that higher precipitation during the period of seed development, along with moderate air temperature, affected thiamine accumulation of some soybean genotypes more than others.

Spectrofluorometric method for determination of the total mercury content in natural waters.

ZusammenfassungEs wurde eine einfache, schnelle und hochselektive spektrofluorometrische Methode zur quantitativen Bestimmung des Gehalts an Gesamtquecksilber in Wasser beschrieben. Diese empfindliche Methode begründet sich auf der Fluorescenzlöschung in Rodamin-B-Lösung mittels Hg(II) bei Anwesenheit von Jodid und nach einem Verfahren, das den Zweck einer Quecksilberanreicherung hat. In Wasserproben wurden die organischen als auch anorganischen Quecksilberverbindungen mit H2SO4 aufgeschlossen und mit KMnO4 oxydiert. Nach der Beseitigung des entstandenen MnO2-Niederschlags bzw. des überschüssigen Permanganats mit HONH3Cl wurde das Quecksilber mit SnCl2 reduziert. Dann wurde das flüchtige Quecksilber durch einen Luftstrom in wässerige Absorptionslösung mit H2SO4 und KMnO4 eingeleitet und damit angereichert. In dieser Meßlösung wurde die Fluorescenzlöschung des Rodamin-B bei der Anregungswellenlänge von 485 nm und Emissionswellenlänge von 586 nm ermittelt. Das entwickelte Untersuchungsverfahren ist für die Bestimmung des Gehalts an Gesamtquecksilber in Trinkwasser und Oberflächengewässern anwendbar. Die Nachweisgrenze liegt bei etwa 0,5 μg Quecksilber/L Wasser. Zusätze von Quecksilber zu untersuchten Wasserproben ergaben eine Wiederfindungsrate und Standardfehler von im Durchschnitt 97,3±2,39.AbstractA simple and highly selective spectrofluorometric method for the determination of the total mercury (Hg) in natural waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, has been made the basis of this sensitive method. Organic and inorganic Hg compounds in water samples were decomposed with sulphuric acid and potassium permanganate. Precipitated manganese dioxide and excess oxidants (permanganate) were destroyed with hydroxylammonium chloride. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. This method is suitable for the determination of total Hg in drinking and surface waters. The method gives reliable results down to a concentration of 0.5 μg Hg per litre of water. The water samples analysed by this method gave a mean recovery and standard error of 97.3±2.39 for added Hg.