G. Tölg

Aufschluß biologischer Matrices für die Bestimmung sehr niedriger Spurenelementgehalte bei begrenzter Einwaage mit Salpetersäure unter Druck in einem Teflongefäß

For the determination of trace elements (< 10−4%) in biological materials (e.g. tissue, food, sewage muds) in samples ≤ 500 mg a pressure decomposition with nitric acid or a mixture of nitric and hydrofluoric acid in a teflon tube is described. The recoveries for the volatile elements, e.g. Hg, Se and I, in the ng-range were investigated by the tracer method and were found to be ≥ 98%.ZusammenfassungFür die Bestimmung von Spurenelementgehalten (< 10−4%) in biologischen Matrices (Gewebe, Nahrungsmittel, Abwasserschlämme u. a.) bei begrenzten Einwaagen (≤ 500mg) wird ein Druckaufschluß mit HNO3 bzw. HNO3-HF in einem Teflongefäß beschrieben. Radiochemische Messungen ergaben, daß die Verluste selbst bei Nanogramm-Mengen flüchtiger Elemente (Hg, Se, J u.a.) unter 2% liegen.

Platinum traces in airborne particulate matter. Determination of whole content, particle size distribution and soluble platinum

SummaryDuring a period of almost one year airborne dust was collected at the area of ISAS, Dortmund. The total platinum content varied from 0.6 to 130 µg/kg, respectively from 0.02 to 5.1 pg/m3. The impactor measurements resulted in an equal distribution of platinum in combination with particle sizes ranging between 0.5 and 8 µm. The lowest concentrations were observed for the larger particles (>8μm). The “soluble platinum” in airborne dust was determined to be 30 to 43% of the total amount of platinum and 2.5 to 6.9% in tunnel dust.

Adsorptive voltammetric procedure for the determination of platinum baseline levels in human body fluids

SummaryAn extremly sensitive procedure for the determination of platinum in human body fluids is presented. A high pressure decomposition of the samples is followed by adsorptive voltammetric measurement. A detection limit down to 0.2 ng Pt/l sample allowed baseline levels of platinum in body fluids (urine: 0.5–15 ng/l, blood and blood plasma: ≤0.8–6.9 ng/l) to be evaluated. The concentration ranges in body fluids of occupationally exposed people were determined to 21–2900 ng/l (urine), 32–180 ng/l (blood) and 95–280 ng/l (blood plasma).

Extreme trace analysis of the elements-I Methods and problems of sample treatment, separation and enrichment.

In the determination of elements in the ppM range in inorganic and organic matrices, solution techniques are useful because they simplify calibration problems and improve the limit of detection. The author reviews, in the light of his own experience, some 350 publications concerned with methods for the preparation and dissolution of samples and for the isolation of trace elements before their determination. The errors in these methods, made more difficult to reduce because of the additional operations required, are compared with those associated with the more direct methods.

Preconcentration of palladium, platinum and rhodium by on-line sorbent extraction for graphite furnace atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

A flow system combined with a segmentation technique was used to develop an efficient on-line sorbent extraction preconcentration system for palladium, platinum and rhodium for graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The investigated metals were preconcentrated as their bis(carboxylmethyl)dithiocarbamate (CMDTC) chelates on a microcolumn packed with XAD-4 after the off-line addition of solid CMDTC to the sample solution containing SnCl2 and hydrochloric acid. The sample, rinsing and eluent solutions were segmented by air to prevent dispersion. The eluate was collected on-line in a PTFE loop and was forced either into the graphite tube by nitrogen or into the ICP by using a carrier solution. The time duration of one preconcentration cycle was about 10 min. The influence of the acidity of the synthetic sample solution, the concentration of the complexing reagent and reducing agent, the flow-rate for preconcentration, the efficiency of the desorption and the influence of various matrices were also investigated. The detection limits (3σ) were 0.03, 0.1 and 0.01 ng/ml for Pd, Pt and Rh, respectively, using GFAAS detection. The method was applied for the analysis of polluted biological materials.

A Survey of selenium in the environment and a critical review of its determination at trace levels

ZusammenfassungEs gibt heute ausreichende Beweise für die Annahme, daß Selen dem Wachstum der Pflanzen förderlich und für Tier und Mensch sowohl ein essentielles als auch giftiges Spurenelement ist. Die vorliegende Arbeit gibt einen Einblick in die Rolle, die Selen in Umwelt und Biologie spielt. Aufmerksamkeit wird hauptsächlich auf Vorkommen, Verteilung und Anreicherung des Elements in der Öko- und Biosphäre gelegt, aber auch auf toxische Effekte, Wechselwirkungen mit Begleitelementen und auf die Essentialität für Tier und Mensch. Die Bestimmung von Selenspuren in umweltrelevanten Matrices, unter Berücksichtigung von systematischen Fehlern, wird jedoch besonders hervorgehoben. Ein umfassendes Literaturstudium ermöglichte einen Vergleich der am häufigsten verwendeten Bestimmungsmethoden und ihrer Leistungsfähigkeit.SummaryThere is sufficient evidence today to assume that selenium has beneficial effects on the growth of plants, and that it is both an essential and toxic trace element for animal and man. This review article intends to show the involvement of selenium in the environment and in biology. Attention is paid, in large, to the occurrence, distribution and accumulation of the element in the eco- and biosphere, but also to toxic effects, interactions with concomitant elements and to the essentiality to animals and humans. Special emphasis is, however, placed on the determination of selenium at trace levels with consideration of systematic errors in environmentally relevant materials. A comprehensive literature search was carried out in order to provide an appropriate overview of the most commonly used analytical methods and their limitations.

Zur Ursache und Vermeidung systematischer Fehler bei Elementbestimmungen in wäßrigen Lösungen im ng/ml- und pg/ml-Bereich

SummaryConsiderable discrepancies have been found between theoretically derived detection limits in literature for the determination of elements in the extreme trace range and actually found results for high-purity materials. This caused us to study the systematic errors (blanks, adsorption and desorption) of solution procedures. The sources of systematic errors by contamination are demonstrated by example of the determination of magnesium and zinc at pg/ml levels by AAS with electrothermal atomization. These sources of the blanks mainly determine the actual detection limits of solution procedures and appear even in very simple operations, e.g., preparation, measuring, storage, filtration and evaporation of solutions. Possibilities for eliminating these errors are: selection of suitable vessel materials and reagents and their effective cleaning resp. purification as well as working in clean rooms under extreme conditions. The exemplary studies show the actual obtainable detection abilities, which may differ — depending on the element — from the idealized and unrealistic values of the literature.ZusammenfassungErhebliche Diskrepanzen zwischen theoretisch abgeleiteten, in der Literatur angegebenen Nachweisgrenzen von Elementbestimmungsverfahren im extremen Spurenbereich und den real gefundenen Ergebnissen im Rahmen der Reinststoffanalytik gaben Anlaß, systematische Fehler (Blindwerte, Adsorption und Desorption) bei Lösungsverfahren grundlegend zu untersuchen. Am Beispiel der Bestimmung von Magnesium und Zink im pg/ml-Bereich durch AAS mit elektrothermischer Atomisation werden die Quellen für Kontaminationen nachgewiesen, die in erster Linie die realen Nachweisgrenzen der Lösungsverfahren bestimmen und schon bei den einfachsten Operationen wie Bereitung, Abmessen, Aufbewahren, Filtrieren und Eindampfen von Lösungen auftreten. Möglichkeiten zu ihrer Ausschaltung sind: Auswahl geeigneter Gerätematerialien und Reagentien und deren Reinigung sowie das Arbeiten in staubarmen Laboratorien (Reinen Räumen) unter extremen Reinheitsbedingungen. Die exemplarischen Untersuchungen zeigen die praktisch erreichbaren Grenzen des Nachweisvermögens, das sich elementabhängig z. T. wesentlich von den idealisierten und unrealistischen Literaturwerten unterscheiden kann.

Wet mineralization of organic matrices in glassy carbon vessels in a pressure-bomb system for trace element analysis

Glassy carbon (Sigradur G(R)) is thermally stable up to 600 degrees under atmospheric conditions and has proved to be substantially resistant to many decomposition agents at temperatures up to 250 degrees . It can, therefore, substitute for PTFE vessels in a pressure-bomb device for the wet decomposition of organic and inorganic substances with, e.g., nitric, chloric or hydrofluoric acid or mixtures thereof, in the determination of trace elements. The mineralization can be carried out at temperatures up to 50 degrees higher than with PTFE vessels, which are limited to a maximum of 170 degrees . The higher decomposition temperature, which results in a higher oxidation potential, considerably shortens the decomposition time. On account of the lower content of impurities, particularly of Hg, Ag, Bi, Cd, Se, Te and Sb, the results are more accurate than those obtained with PTFE vessels, if these elements are to be determined in the ng/g range in the resulting solution.

Different sample introduction systems for the multaneous determination of As, Sb and Se by microwave-induced plasma atomic emission spectrometry

Abstract The determination of hydride-forming elements using different sample introduction procedure into microwave-induced plasmas (MIPs) has been studied. For the determination of As, Sb and Se analyte introduction was accomplished with a pneumatic concentric glass nebulizer,a graphite furnace, or with thydride generation followed by cold-trapping or hot-trapping in a graphite furnace. The detection limits obtained with different types of low power MIPs (toroidal, 1 or 3 filament MIPs) operated in a TM 010 cavity according to Beenakker also were investigated. The contruction of the flow system used for preconcentration and the effects of reagent concentration, gas flow rates as with MIP-atomic emission spectrometry (AES) were investigated. The trapping of the hydrides followed by their vaporization showed substantial advantages over the other introduction systems investigated, especially with respect to power of detection. Further, mutual interferences being a big problem in atomic absorption spectrometry are widely absent in MIP-AES. Under compromise operating conditions the detection limits for As, Sb and Se are 0.4; 0.35; 0.25 ng ml −1 respectively, while the sample volume can be varied from 0.05 ml up to several millilitres.

Platinum species analysis in plant material by gel permeation chromatography

Abstract Model experiments for the analysis of platinum species in extracts from native and platinum treated grass cultivation are described. The procedural steps are cultivation of the grass samples, preparative separation of the Pt species and analytical detection and characterisation of the separated species. The platinum uptake from the roots resulted by treating the grass cultivation with an aqueous solution of tetrammineplatinum(II) nitrate, [Pt(NH 3 ) 4 ](NO 3 ) 2 . The grass was cut, the cell fluid extracted and the Pt species were separated by gel permeation chromatography. The extremely sensitive adsorptive voltammetry was used for the sequential determination of platinum in the elution fractions. The estimation and determination of the molecular weights were carried out by gel permeation and liquid chromatography. In the native grass extract only one Pt species (160–200 kD) was detected. In the platinum treated grass extracts several Pt species were observed. More than 90% of all the platinum is bound to a low molecular weight species (about 1 kD), whereas less than 10% of the platinum is bound to species with molecular weights from 19 up to > 1000 kD.