K. H. Lieser

Transition metals in atmospheric aqueous samples, analytical determination and speciation

SummaryTwo rain water samples were analyzed with respect to the determination of the species which are present at the given conditions. The parameters determined were: pH, Eh, electrolytical conductivity, concentration of anions (SO42−, NO3−, Cl−, NO2−, HCOO−, CH3COO−), of main cations (Na+, K+, NH4+, Mg2+, Ca2+), and of transition metals (V, Cr, Mn, Fe, Co, Cu, Zn). The methods used were filtration and ultrafiltration, voltammetry, sorption on various sorbents and ion chromatography. Furthermore, Eh-pH-diagrams were taken into account and the partition of the species was calculated by means of stability constants. The transition elements species in the atmospheric aqueous solutions are discussed.

Cellulose exchangers with tailor-made chelating groups for selective separation of uranium

SummarySeveral tailor-made cellulose exchangers are investigated with respect to their properties (capacities, distribution coefficients for UO22+, Fe3+, Ni2+, Cu2+, Pb2+ as function of pH, and half-time of exchange). The chelating anchor groups are: 8-oxa-2,4,12,14-tetraoxopentadecane, malonic acid groups linked together by n-alkanes of various chain length, amidoxime/hydroxamic acid groups and amidrazone/hydrazide groups, also linked together by n-alkanes. The anchor groups are fixed by chemical bonds on cellulose, they are flexible and selected for sixfold coplanar coordination of UO22+. The distribution coefficients are determined in simulated sea water at the same initial concentrations of heavy metal ions [1 mg/1 of UO22+, Fe3+, Ni2+, Cu2+, Pb2+, (Zn2+), each]. Kd(UO22+) depends on the steric conditions and on the properties of the donor groups. Under favourable conditions very high values of Kd(UO22+) are found, up to log Kd(UO22+)=5.5 (Kd in ml/g) and also high selectivities for UO22+. The influences of the donor groups, of the steric conditions and of the competition between formation of chelates with the anchor groups and formation of the triscarbonato complex [UO2(CO3)3]4− in solution are discussed.

Determination of trace elements in water by non-destructive neutron activation

A systematic study was undertaken in order to find out which of the most relevant elements can be determined in water under normal conditions by non-destructive neutron activation simultaneously using a suitable monostandard method. Standardized water samples as well as natural water of different kind were used, brought to dryness by freeze-drying and irradiated in quartz at a neutron flux of 1014 cm−2 s−1 for 1 day. The trace element content in quartz ampoules of different origin was determined separately. The following elements are discussed in detail including possible interferences: As, Au, Br, Ca, Cd, Co, Cr, Cu, Eu, Fe, Hg, K, La, Mo, Na, Ni, Sb, Sc, Se, U, Zn.

Actinides in the environment

The influence of the following parameters is discussed: oxidation state (Eh), hydrolysis (pH), solubility, complex formation, colloid formation, sorption and filtration effects. The oxidation states of the actinides in neutral aqueous media are plotted as a function of the redox potential. Hydrolysis, stability of 1∶1 carbonato complexes, of humic acid complexes and solubilities of the hydroxides in the various oxidation states are considered. Mobility is investigated as a function of pH by paper chromatography. Partition of the actinides in groundwaters on the molecular fraction, the fine particle (colloid) fraction and the coarse particle fraction is determined as a function of pH by filtration and ultrafiltration. Sorption ratios are measured as function of pH, salt concentration and of EDTA concentration. When the groundwaters are passed through the sediments, mainly the coarse particle fractions are retained by size filtration. The pronounced influence of the redox potential on sorption is demonstrated for Np.

Neutron activation as a routine method for the determination of trace elements in water

By freeze-drying the following elements can be determined in natural water except sea water: Au, Ba, Br, Ca, Ce, Co, Cr, Eu, Fe, K, La, Mo, Na, Sb, Sc, Se, U, Zn. Some problems may arise with respect to As and Hg. Cu, Cd and Ni can only be determined if present in high concentrations. Separation by adsorption on charcoal in presence of complexing agents gives yields between 75 and 100% for the following elements in sea water: Ag, Au, Cd, Ce, Co, Cr, Eu, Fe, Hg, La, Mo, Sc, Se, U, Zn (As 67%, Sb 56%). Activation or use of labelled ions and study of exchange give information about mobility of trace elements in suspended matter.

Abtrennung von Spurenelementen aus Wasser mit Hilfe von Celluloseaustauscher-Filtern und ihre Bestimmung durch Röntgenfluorescenzanalyse mit Radionuklidanregung

For the separation of trace elements from water cellulose containing chromotropic acid as functional group is used in form of thin filters (capacity 0.0075 mEq.). The time necessary for the filtration of 100 ml is about 10 min. The behaviour of the elements Fe, Cu, Zn, Sr and Hg is studied in detail. Fe, Cu, Zn and Sr are fixed on the filter in the range from pH 4–6.5 with a yield >90%, provided the content of the elements does not exceed the capacity of the filter. Larger amounts of calcium ions or sodium ions interfere considerably with the separation of the elements mentioned above. The filters are used directly for analysis by X-ray fluorescence. Calibration curves for the elements with atomic number 25–38 are presented. For comparison Chelex filters are investigated, too. The advantages and disadvantages in the use of the cellulose filters are discussed.ZusammenfassungFür die Abtrennung von Spurenelementen aus Wasser wird ein Celluloseaustauscher mit Chromotropsäure als funktioneller Gruppe in Form von dünnen Filtern verwendet (Kapazität etwa 0,0075 mÄq.). Die Filtrationszeit für 100 ml Wasser beträgt etwa 10 min. Das Verhalten der Elemente Fe, Cu, Zn, Sr und Hg wird näher untersucht. Fe, Cu, Zn und Sr werden im pH-Bereich von etwa 4–6,5 mit einer Filtrationsausbeute >90 % festgehalten, sofern der Gehalt die Kapazität des Filters nicht übersteigt. Größere Gehalte an Calcium-Ionen oder Natrium-Ionen stören die Abtrennung erheblich. Die Filter werden direkt für die Röntgenfluorescenzanalyse verwendet. Eichkurven für die Elemente mit den Ordnungszahlen 25–38 werden angegeben. Zum Vergleich werden Chelex-Filter herangezogen. Die Vor- und Nachteile der Verwendung von Celluloseaustauscher-Filtern werden diskutiert.

In-line determination of U, Pu and Np in process streams by energy-dispersive X-ray fluorescence analysis (EDXRF)

A γ-ray source of ≈300 keV was used in order to excite the fluorescent K-radiation of the heavy elements which is only weakly absorbed in the walls of metal tubes. Thus, uranium can be determined quantitatively in solutions within tubes in the concentration range form 5 mg/l to 100 g/l. The influences of the energy and the activity of the radiation source, the geometrical arrangement, the thickness of the wall and the wall material have been investigated.

Application of X-ray fluorescence analysis with total-reflection (TXRF) in material science

SummaryA device was constructed to determine elements of low atomic number by non-destructive TXRF analysis. It consists of a Cr-X-ray tube, an optimized reflection unit, a detector with an extremely thin entrance window, a low noise amplifier, and a sample changer. To minimize the absorption losses, the main parts are placed in a vacuum chamber with a very thin Be window. Using this arrangement it is possible to measure elements down to oxygen from the pg- to the ng-range.

Separation and determination of S-anions in very small samples by microbore ion chromatography

SummaryBy modification of a given conventional high pressure liquid chromatography (HPLC) unit a microbore system was built up useful for separations of S-containing anions in small aqueous samples. The sample volume could be lowered down to 0.5 μl. Mixtures of a lipophilic reagent (TPAOH or TBAOH) with boric acid and acetonitrile were used as eluents.

Preconcentration and determination of trace elements in fresh water and sea water

Der Spurenelementgehalt in standardisiertem Wasser, in Rheinwasser und Meerwasser wird durch Neutronenaktivierungsanalyse (NAA), Rontgenfluorescenzanalyse (RFA) und Atomabsorption (AAS, mit Ausnahme von Meerwasser) bestimmt. Die Voranreicherung erfolgt fur NAA durch Gefriertrocknung und Schutteln mit einem Celluloseaustauscher (CA), fur RFA durch Abtrennung in CA-Saulen, Filtration durch CA-Filter oder Schutteln mit CA. Die Ergebnisse werden verglichen und diskutiert.ZusammenfassungDer Spurenelementgehalt in standardisiertem Wasser, in Rheinwasser und Meerwasser wird durch Neutronenaktivierungsanalyse (NAA), Röntgenfluorescenzanalyse (RFA) und Atomabsorption (AAS, mit Ausnahme von Meerwasser) bestimmt. Die Voranreicherung erfolgt für NAA durch Gefriertrocknung und Schütteln mit einem Celluloseaustauscher (CA), für RFA durch Abtrennung in CA-Säulen, Filtration durch CA-Filter oder Schütteln mit CA. Die Ergebnisse werden verglichen und diskutiert.SummaryTrace elements in standardized water, in Rhine water and sea water were determined by neutron activation (NAA), X-ray fluorescence (XFA) and atomic absorption (AAS, except for sea water). Preconcentration was effected for NAA by freeze-drying and shaking with a cellulose exchanger (CA), for XFA by separation in columns filled with CA, filtration through CA-filters or shaking with CA. The results obtained are compared and discussed.