Zur Röntgenfluoreszenzanalyse metallorganischer Verbindungen

Control of foodstuffs with respect to radioactivity requires in many cases previous ashing of the samples. A method for dry ashing is described which requires little time. It is possible to ash a 500–1000 g sample of water-containing food (fruits, vegetables etc.) as well as liquid food (milk, fruit juices etc.) without previous drying in 30–90 min at about 500° C. Interactions between the moist and liquid foodstuffs and the stainless steel ashing vessels during the ashing was avoided by using appropriate inert layers. The temperature increase of the samples generated by oxydation processes was measured by immersed thermocouples. Because of the volatility of certain inorganic constituents, knowledge of the temperature change in the ashed sample is important. The degree of volatility and the influence of the ashing temperature on the acid solubility of some nuclides was measured. Of the 12 elements investigated, only the Ru/Rh isotopes exhibited a pronounced dependence of the acid solubility on the ashing temperature.     

Ashing and microwave digestion of aerosol samples with a polypropylene fibrous filter matrix

Radionuclide monitoring is one of the key techniques required by the International Monitoring System (IMS) and On-Site Inspection (OSI) in the Comprehensive Nuclear Test Ban Treaty (CTBT). There shall be a global network of 80 radionuclide monitoring stations. Atmospheric aerosols are collected generally on filters in the stations. A polypropylene (PP) fibrous filter is often used in sampling atmospheric aerosols. There might be much information to be obtained by measuring aerosol samples after digestion rather than nondestructive analysis directly by γ-spectrometry. The present work focused on pretreatment of the filter samples, which includes the influence of different ashing or microwave digestion conditions on the recoveries of analytes. The inductively coupled plasma-atomic emission spectrometric detection results indicated that the recoveries of elements in the PP fibrous filters by ashing were influenced by ashing time, temperature and the properties of the elements. High recoveries of volatile elements and consistent recovery for other elements were obtained by using a closed microwave system to digest the filters. Higher sensitivity was also obtained when the intercomparison sample was measured by a HPGe well detector after pretreatment by the recommended ashing and microwave digestion procedures.     

Combination of classical dry ashing with stripping voltammetry in trace element analysis of biological materials: review of literature published after 1978

Critical statements have appeared recently in the literature concerning the need for classical dry ashing in trace element analysis of biological materials. In contrast, respected institutions (AOAC, Nordic Committee on Food Analysis, etc.) as well as numerous other laboratories have developed, verified, and/or successfully used classical dry ashing in practical analyses of a number of materials of biological origin. Hence, it is desirable to find out under which conditions the latter decomposition technique yields good and accurate results. Since electroanalytical techniques are among the most demanding with regard to the completeness of the biological matrix removal, we decided to critically review the literature published after 1978 in which classical dry ashing is combined with some version of electroanalytical measurement. It emerged from this review that in particular the charring step requires careful performing. When performed well, classical dry ashing leads to complete removal of the organic matrix and to accurate analytical results for a number of determined elements.     

氧等离子体低温灰化法测定生物样品灰分中易挥发元素

本文介绍了氧等离子体低温灰化法及我们设计研制的氧等离子体低温灰化装置在多种样品处理中的应用。结果表明;本法对样品中含有的易挥发元素可取得良好的回收率,仪器具有较好的适用性、可靠性。     

Preparation of conducting electrodes from biological samples for multi-element trace analysis by spark-source mass spectrometry or emission spectrometry

Four decomposition procedures frequently used for biological material (dry ashing, open wet digestion, wet digestion in a teflon bomb and low-temperature ashing) are optimized for the conversion of biological samples to conducting electrodes suitable for multi-element trace determinations by spark-source mass spectrometry or emission spectrometry. The optimized procedures are evaluated with respect to contamination, retention and preconcentration of the trace elements, homogeneity of the electrodes and precision of the final results. Both dry-ashing methods are prone to losses by volatilization; simple dry ashing suffers from contamination problems during electrode preparation. Wet digestion gives better precision; digestion with nitric/sulfuric acids in an open flask is the method of choice for most elements being simpler and giving lower blanks than the bomb method.     

野生中草药木贼中微量元素的测定

目的测定中草药木贼中微量元素的含量。方法用湿法消化及于法灰化两种方法处理样品并进行了比较,用火焰原子吸收法测定了中草药木贼中7种微量元素的含量。结果测定结果湿法的RSD在0．5％～3．0％,干法的RSD在0．5％-7．5％之间。结论湿法处理金属离子损失小,测量精密度更好。木贼中微量元素的含量由高到低顺序为：Mg,Fe,Mn,Zn,Cu,Ph,Ni。     

Spectrochemical cobalt,molybdenum and copper determinations in plants

This paper deals with the spectrochemical determination of some trace elements (Cu, Mo and Co), especially in plant samples. Data are given about the choice of light source and spectral apparatus, as well as detailed remarks concerning the optical arrangement.In the concentrating pretreatment with precipitating chemicals a wet ashing has been proved to give better results than a dry ashing.     

Losses of elements in plant samples under the dry ashing process

Losses of trace elements in plant samples after dry ashing were investigated. Plant samples were heated in crucibles at 105–600°C for 0.5–24 hours in a muffle furnace. The amounts of elements remaining after heating were determined by INAA. The amounts of Cl and Br decreased over the range 200–400°C in all samples, especially in stem samples. The amount of Na increased over the range 450–600°C, possibly because of contamination from the crucibles. Dry ashing is suitable for analyzing most elements in plant samples.     

An apparatus for the wet ashing of organic matter

An apparatus for the wet ashing of organic material is described. It makes possible the ashing of large quantities of organic matter with pure, ash-free reagents and the determination of various constituents in the samples. This procedure is most useful for the determination of trace elements. It has mainly been used so far for the determination of small amounts of sulfur.     

Cold plasma ashing improves the trace element detection of single Daphnia specimens by total reflection X-ray fluorescence spectrometry

The recently developed dry method for the element determination of single freshwater microcrustacean specimens (Daphnia) using total reflection X-ray fluorescence (TXRF) spectrometry showed that inhomogeneities of the biological material on the glass carriers resulted in some cases in high background and hampered the detection of certain trace elements (e.g. Cr, Ni). The aim of this study was to test how inhomogeneities of the biological material can be reduced using cold plasma ashing (CPA) techniques. For that, single specimens of the microcrustacean Daphnia pulex prepared according to the dry method were measured by TXRF before and after CPA. To determine the efficiency of the removal of organic matrix, the background and signal-to-background relationship of 28 samples were analyzed. The results showed (1) a highly significant reduction of the background by CPA fluctuating between 26 and 46% (all elements) and (2) a significant increase of the signal-to-background relationship by the factor 1.5–2.5 (all elements) and a much better detection of Cr, Pb, As and Se. The element concentrations (with exception of Cr, Ni and Pb) after ashing were in the same range or slightly higher than that before ashing. No significant differences between the two treatments were observed for Mn, As, Pb, Se (November), Sr (November), Cr (March) and Pb (March). The element concentration of P, K, Ca, Cu, Zn, Cr (November), Fe and Rb were significantly higher after ashing. In general, they increased by 1.5–13.6% and were highest for Rb (March) and P (November). In contrast, the element concentration of Ni and Cr (only March) decreased significantly after ashing (Ni: 91.6–92.1%, Cr: 91.3%). We recommend the use of CPA for biological material in the microgram-range as a routine method for TXRF analysis, especially when trace elements in minute concentrations are of interest.     

Detection of air pollution sources in israel by isotope-induced XRF

Aerosol samples from urban, industrial and traffic areas were collected and analyzed for various elements. The correlation between the multielement content of the samples and their sources was studied. It was found necessary to anlayze samples before and after ashing because, while ashing improves the peak-to-background ratio, volatile elements may be lost. Samples collected at heights of 1.5 and 15 m were found to have the same elemental composition. Samples collected on consecutive filters showed sharp elemental fractionation An example of source identification is given for a high traffic area as compared with an area in which a large bromine plant is located. In both cases different Pb∶Br ratios were observed, with high bromine concentration in the latter. The analytical method used was based on the detection of characteristic K and L X-rays induced by a²⁴¹Am-I source-target assembly.     

Trocknung und Veraschung biologischer Proben bei der neutronenaktivierungsanalytischen Spurenelementbestimmung

The changes in the element content of blood serum samples due to drying and ashing procedures were investigated for those trace elements which could be determined by instrumental neutron activation analysis after long-time irradiation (Ag, Co, Cr, Cs, Fe, Rb, Sb, Sc, Se, and Zn). For some elements lower concentrations were found after oven-drying at 90° C and after low temperature ashing than after freeze-drying. In the case of selenium, which is known to form several volatile compounds, no differences could be detected between the freeze-dried, oven-dried and ashed samples.     

Determination of trace elements in plant materials by inductively coupled plasma optical emission spectrometry

The use of inductively coupled plasmas as spectrometric emission sources for the determination of Fe, Mn, Cu, Al, B and Zn in orchard leaves is investigated. The plasma is shown to be sufficiently sensitive for the direct determination of all of the above elements in solutions of the plant materials after a dry ashing procedure. Comparative values for the trace element concentrations by other analytical methods are given.     

Speciation of the inorganic components in brown coal

Brown coal samples from different deposits have been analyzed for the bonding forms of their inorganic components. Besides the analysis of the dried coals, ashing techniques (high and low temperature ashing) and extraction procedures with different solvents (acids, bases, complexation agents, organic solvents with different polarity) have also been investigated. ESCA, PIXE, INAA, ICP-Atomic Emission Spectroscopy, NMR and Ionchromatography have been applied to the analysis of coals, ashes, wet ashing and extraction products. The bonding behavior of more than 40 elements could be characterized. Conclusions about geological and geochemical processes during and after coalification could be drawn.     

The role of metallic matrix modifiers in graphite furnace atomic absorption spectrometry

The role of metallic matrix modifiers in AAS is considered; for elements reduced, together with modifier elements, during ashing and the beginning of the atomization process, the thermodynamic activity and melting points of the alloys formed are important. For Mg²⁺, prevention of the effects of halide ions is considered, as is also the behaviour of buffer and/or carrier in emission spectrometric analysis of the other alkali and alkaline earths.     

Elements analysis of infant milk formula by ICP-OES: a comparison of pretreatment methods

Sample pretreatments are critical steps for achieving true and precise results in element analysis for infant milk formula. In this study, we made a comparative study of four pretreatment methods: dry ashing (DA), wet ashing (WA), microwave ashing (MA) and slurry dispersion analysis. Nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) were determined by inductively coupled plasma optical emission spectrometry. Infant formula (GBW08509) with certified values was used for assessment of trueness and precision. The data showed that all relative standard deviations (RSD) of the observed values were <15 %. In contrast to other pretreatment, results for MA had the lowest RSD (≤5 %) for all the elements. For Cu and Mn, there was no significant difference between measurement results and certified values in four pretreatments. But, after DA and WA the results for Ca, K, Na, P and Zn differed significantly from the certified values.     

Total-Reflection X-ray fluorescence analysis of elements in size-fractionated particulate matter sampled on polycarbonate filters — Composition and sources of aerosol particles in Göteborg,Sweden

This is the first study applying the technique of cold plasma ashing on polycarbonate filters as a preparative step for subsequent elemental analysis of aerosol particles by Total-Reflection X-ray fluorescence. The procedure has been validated by analyzing blanks of the filter material, chemicals used as additives as well as certified standard reference material. The results showed that cold plasma ashing is superior to conventional digestion methods with regard to the ease of sample preparation and contamination. A PIXE cascade impactor was used to collect size-fractionated aerosol particles in 9 size classes ranging from 16 to 0.06 µm aerodynamic diameter at an urban and a suburban site in Göteborg, Sweden. Filter segments loaded with the aerosol particles were cut out and fixed on Quartz carriers. After adding 10 ng of Ga as internal standard the samples were dried, digested by cold plasma ashing and analyzed by Total-Reflection X-ray fluorescence. The analysis of aerosol particles showed that elemental concentrations at both the urban and the suburban site in Göteborg were low compared to central Europe. More and concurrent sampling of size-fractionated particles is required to identify local sources of trace elements in the urban area of Göteborg.     

Determination of calcium, potassium, manganese, iron, copper and zinc levels in representative samples of two onion cultivars using total reflection X-ray fluorescence and ultrasound extraction procedure

The chemical characterization of onion cultivar samples is an important tool for the enhancement of their productivity due to the fact that chemical composition is closed related to the quality of the products. A new sample preparation procedure for elemental characterization is proposed, involving the acid extraction of the analytes from crude samples by means of an ultrasonic bath, avoiding the required digestion of samples in vegetable tissue analysis. The technique of total reflection X-ray fluorescence (TXRF) was successfully applied for the simultaneous determination of the elements Ca, K, Mn, Fe, Cu and Zn. The procedure was compared with the wet ashing and dry ashing procedures for all the elements using multivariate analysis and the Scheffé test. The technique of flame atomic absorption spectrometry (FAAS) was employed for comparison purposes and accuracy evaluation of the proposed analysis method. A good agreement between the two techniques was found when using the dry ashing and ultrasound leaching procedures. The levels of each element found for representative samples of two onion cultivars (Yellow Granex PRR 502 and 438 Granex) were also compared by the same method. Levels of K, Mn and Zn were significantly higher in the 438 Granex cultivar, while levels of Ca, Fe and Cu were significantly higher in the Yellow Granex PRR 502 cultivar.