Enrichment techniques in inorganic trace analysis. Present status and future prospects

Analytical and Bioanalytical Chemistry - Preliminary enrichment is indispensable for inorganic trace analysis, to lower the detection limits, improve the precision and accuracy, and widen the scope...     

Sampling and storage of materials for trace elemental analysis

Accurate analysis depends upon a valid, representative and uncontaminated analytical sample. For many trace metals, contamination overwhelms the sample, leading to inaccurate analytical data. Methods of controlling contamination and their implications for better methods of sampling and storage are discussed here.     

Collection and preparation of sidestream cigarette smoke for trace elemental determinations by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

A novel method for the collection and preparation of sidestream cigarette smoke condensate is described for trace elemental analysis by inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry. The smoke collection method utilizes a specially designed chimney that collects and directs the sidestream smoke (SS) to a 2-stage trapping system consisting of an impaction trap followed by a 0.8 microm mixed cellulose ester filter. The samples are digested with nitric acid in a commercial heating block before analysis. The method limits of detection (LODs) are 1, 0.2, 2, 9, 6, and 7 ng/cigt for As, Cd, Pb, Ni, Se, and Cr, respectively. The SS collected from an industry reference cigarette, 1R4F, produced by the University of Kentucky was analyzed. The concentrations of As, Cd, and Pb in 1R4F were determined to be 27.3+/-2.1, 412+/-14, and 43.8+/-2.0 ng/cigt, respectively, while the concentrations of Ni, Cr, and Se are below the method LOD. Consequently, this novel method successfully addresses contamination, instrumentation, and collection issues for performing trace elemental analysis of sidestream cigarette smoke condensate.     

The present and future of graphite furnace atomic absorption spectroscopy

Graphite furnace atomic absorption spectroscopy (AAS) technology has been greatly improved since the late 1970s and the new technology is now being used widely. The chief characteristic of the new technology is its remarkable freedom from interference while retaining the high sensitivity of graphite furnace AAS. Thus, an important goal of continuing furnace research is to identify interferences that persist and, by understanding the causes of residual interference, make further improvements to the system. Several background correction systems have been used.Furnace AAS remains a slow analytical technique, typically about 2 min per analyte and sample. One way to speed throughput is to use simultaneous multielement analysis although this is not easily compatible with the modern furnace. Inherently, the photometric range of furnace AAS has been more limited than, say, inductively coupled plasma but there are now ways to improve the range of furnace measurements. Alternatively, furnace emission provides a potential multielement opportunity, especially if the emission signal is enhanced with an electric discharge.The reduction in matrix interferences increases the opportunity of analyzing solid samples in the furnace. Solid samples may be handled by using well stirred aqueous slurries of finely ground materials. Flow injection analysis, already widely used with flame AAS, provides real potentiality. Perhaps the furnace AAS may become an 'absolute' technique. This will require some changes in the design of the spectrometer and electronic signal handling.     

Direct solid vs. slurry analysis of tobacco leaves for some trace metals by graphite furnace AAS

Summary Graphite furnace atomic absorption spectrometry (GFAAS) is used to determine cadmium, lead, nickel and cobalt in two samples of tobacco leaves (candidate reference materials). Two techniques for the direct determination of these elements are investigated — direct solid sampling into a ring chamber tube specially designed for the Zeiss AAS-3 spectrometer and slurry sampling. For both investigated sampling methods the optimum parameters of temperature-time programs, influence of Pd modifier and calibration methods are discussed. There is acceptable agreement between the results obtained from direct solid, slurry and solution (after wet decomposition) sampling.Presented at the 4th International Colloquium on Solid Sampling with Atomic Spectroscopy, October 8–10, 1990; Jülich, Federal Republic of Germany     

Glow discharge mass spectrometry-a powerful technique for the elemental analysis of solids

A high resolution glow discharge mass spectrometer for the elemental analysis of solids is described. The analytical performance is reviewed and results are presented on a wide range of materials illustrating elemental and concentration coverage, quantitation and detection limits. Comparisons with other techniques are made.     

A temperature-controlled graphite tube furnace for the determination of trace metals in solid biological tissue

A temperature-controlled graphite furnace for atomic-absorption analysis has been built and tested. The temperature of the graphite tube was monitored with an infrared-sensitive detector. Samples were introduced directly or via a separately heated graphite cup. Micro-samples of solid biological tissue were analysed directly for Zn, Mn and Co and the sensitivities for 1% absorption were 0.05,2 and 10 pg respectively. The salt content of the tissue limits the sample sizes, owing to non-specific absorption. The ashing conditions were investigated and found to be especially critical for Zn.     

Application of the graphite furnace to the determination of trace iron in gold and silver

Atomic-absorption analysis using a graphite furnace is a powerful technique for the determination of nanogram amounts of iron. It can be applied to the determination of traces of iron in gold and silver. These metals may be removed from solution by reduction to metallic gold and precipitation as silver chloride respectively. Iron is not co-precipitated. The iron content can be determined in 50-100 mg of the noble metals with an error of about 7% (or 0.1 ppm).     

Direct analysis of solids for trace elements by combined electrothermal furnace/quartz T-tube/flame atomic absorption spectrometry

The analysis of solid samples by a combined graphite-furnace/air-acetylene flame technique based on generally available atomic absorption instrumentation is described. Samples are injected into the furnace and atomized via a slotted T-tube in the flame. Non-specific absorption is greatly reduced compared to that obtained in graphite-furnace atomic absorption spectrometry (a.a.s.). Sensitivity is reduced by 10–200 times compared to the direct graphite-furnace method, so that large sample sizes (up to 0.2 g) can be used; this minimizes problems caused by sample inhomogeneity. The elements considered are cadmium, lead, copper, arsenic, cobalt, mercury, antimony and selenium. Volatile elements such as mercury and arsenic can be determined without the need for a char step. Simple calibration procedures are possible in some cases and the precision is usually better than 10%. Background reduction capabilities are compared with those of conventional graphite-furnace a.a.s., the isothermal-furnace and the hollow graphite T-tube techniques. Analytical capabilities and results are presented for the direct determination of trace elements in numerous biological and some geological samples.     

Thermally expanded graphite: Synthesis, properties, and prospects for use

Results obtained in synthesis of thermally expanded graphite by chemical and electrochemical methods with sulfuric and nitric acids are summarized. The possibility of controlling the properties of thermally expanded graphite compounds in electrochemical synthesis is demonstrated. The existing and promising application areas of thermally expanded graphite are analyzed.     

Determination of trace inorganic selenium in organoselenium (selenosugar) oral nutrition liquids by graphite furnace atomic absorption spectrometry with hydride generation

 A method has been proposed for the determination of trace levels of inorganic selenium in organoselenium (selenosugar) oral nutrition liquids using hydride generation-graphite furnace atomic absorption spectrometry (HG-GFAAS), taking advantage of the fact that this organic selenium compound did not generate volatile hydride upon reduction. K₂S₂O₈ was selected for the decomposition of the compound in a boiling water bath. Selenium was found to give a sharp analytical signal upon reduction with NaBH₄ in 1.0 mol L^-1HCl medium. The characteristic mass giving an integrated absorbance of 0.0044 s was 21 pg. An absolute detection limit (3s) of 36 pg was obtained. The recovery was in the range of 94.2–102.1%. Less than parts per million levels of inorganic Se in the presence of organic selenium can be determined. Received: 7 November 1996/Revised: 13 January 1997/Accepted: 29 January 1997     

Determination of trace inorganic selenium in organoselenium (selenosugar) oral nutrition liquids by graphite furnace atomic absorption spectrometry with hydride generation

 A method has been proposed for the determination of trace levels of inorganic selenium in organoselenium (selenosugar) oral nutrition liquids using hydride generation-graphite furnace atomic absorption spectrometry (HG-GFAAS), taking advantage of the fact that this organic selenium compound did not generate volatile hydride upon reduction. K₂S₂O₈ was selected for the decomposition of the compound in a boiling water bath. Selenium was found to give a sharp analytical signal upon reduction with NaBH₄ in 1.0 mol L^-1HCl medium. The characteristic mass giving an integrated absorbance of 0.0044 s was 21 pg. An absolute detection limit (3s) of 36 pg was obtained. The recovery was in the range of 94.2–102.1%. Less than parts per million levels of inorganic Se in the presence of organic selenium can be determined. Received: 7 November 1996/Revised: 13 January 1997/Accepted: 29 January 1997     

A Further step towards three-dimensional elemental analysis of solids

Summary Three-dimensional constitutional analysis of solid samples has been performed by using a computerized scanning ion-microprobe. Elemental ion currents are stored in each voxel of a three-dimensional scene. Rearranging of voxel data by the computer allows convenient display of three-dimensional data on two-dimensional display media. A particularly useful display mode is the transaxial projection, allowing depth distribution and lateral distribution of an element to be displayed in the same digital image. The inherent resolution limits of this three-dimensional method make it particularly useful in the analysis of microelectronic devices.

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Ein weiterer Schritt zur dreidimensionalen Elementaranalyse von Festkörpern

Zusammenfassung Eine Methode zur dreidimensionalen konstitutionellen Mikroanalyse von Festkörpern wurde beschrieben. In einer computerisierten Ionenmikrosonde werden die Sekundärionenströme in jedem Voxel eines dreidimensionalen Gitters gespeichert, während die Probe vom Primärionenstrahl zerstäubt wird. Durch Umordnen von Voxel-Daten kann Information über die dreidimensionale Elementverteilung in geeigneter Weise auf einem Bildschirm dargestellt werden. In einer neuen Displaymethode, der Transaxialen Projektion, können Lateralverteilung und Tiefenverteilung eines Elementes in einem Festkörper im gleichen digitalen Bild dargestellt werden.

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Presented at the 10th Kolloquium über metallkundliche Analyse, Wien, 3.–5. November 1980.

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Dedicated to Prof. Dr. Hanns Malissa on the occasion of his 60th birthday.     

石墨炉原子吸收法测定石脑油中微量砷

试样用四氢呋喃（THF）有机溶剂稀释,以硝酸镍为基体改进剂,研究采用石墨炉原子吸收法直接进样测定石脑油中的砷量。研究表明,砷量在0～50μg／L范围内线性关系良好,回收率93％～104％。     

石墨炉原子吸收法测定灵芝孢子粉中的痕量硒与锗

有机硒、锗具有抗癌，提高人体免疫的功能，已引起许多研究者的关注。灵芝孢子粉含有丰富的营养成分，如灵芝多糖，灵芝酸，腺苷，18种氨基酸及牛黄酸和特有的矿物元素等均起着奇特的功效，这些营养成分在人体中的功效同样引起许多研究者的重视^[1,2]。本文利用日立Z－8000型原子吸收光谱仪，采用石墨炉法测定有机硒、有机锗。     

Determination of trace impurities in iron and nickel-base alloys by graphite furnace atomic absorption spectrometry

Five approaches to the determination of trace amounts of lead, bismuth, thallium, selenium, tellurium, and silver in iron and nickel-based alloys were investigated. While all procedures produced satisfactory results, direct techniques yielded a significant times advantage over separation schemes. Matrix effects made calibration curves an impractical approach. A spiking technique was used to generate data on a wide range of standard alloy samples.     

Trace analysis of gallium arsenide by graphite furnace AAS

Summary Crystalline and powdered gallium arsenide samples are analysed by graphite furnace AAS. The sample is dissolved in hydrochloric acid and bromine, ammonium chloride as matrix modifier is added and the matrix elements are selectively evaporated as chlorides and bromides in the graphite tube of the atomizer before the atomization step. The temperature programs are optimized. The accuracy of the results was checked by recovery tests and by ICP-OES. The detection limits (g/g) are 0.1 (Ca, Fe), 0.05 (Zn, Pb), 0.03 (Mg), 0.01 (Al, Ni, Cu), 0.005 (Co), 0.002 (Cr) and 0.001 (Mn).

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Spurenanalyse von Galliumarsenid durch Graphitrohr-AAS

     

Graphite furnace atomic absorption analysis of marine samples for trace metals

Trace element determinations by graphite furnace atomic absorption spectrometry which are pertinent to the analysis of marine samples are highlighted. Results for the direct introduction of solids, slurries and dissolved samples of fauna, sediments and saline waters are discussed. Examples drawn from recent literature show that typical samples which benefit most from direct solid sampling are those that do not require the very highest accuracy or precision. No clear consensus amongst users of this technique has emerged regarding the choice between peak height or area recording or the need to standardize by aqueous calibration, the method of additions or use of matrix matched solids. Slurry sampling overcomes several limitations associated with direct solid sampling and whereas generalizations serve little purpose in assessing the applicability of the direct solid sampling approach, slurry sampling holds great promise for widespread use. Examples of external and in situ concentration techniques necessary to augment the relative detection power of the system for the analysis of saline waters are also given. These include an examination of “classical” procedures utilizing chelation-solvent extraction, immobilized ligands and precipitation methods as well as techniques which rely on sequestration in the furnace of volatile analyte species generated in external cells.