Direct solid sample analysis of geological samples with SS-GF-AAS and use of 3D calibration

These results from direct solid-sample trace-element analysis, with 3D calibration, follow those of earlier publications. Cd, Cr, Cu, Ni, Pb, and Zn have been determined in complex inorganic powder samples, e.g. sediments, soils, rocks, and minerals. The measurements were performed with two SS-GF-AAS spectrometers which differ in the type of graphite furnace (transverse and longitudinal tube) and the background-correction technique (with and without the Zeeman system). The performance of the 3D calibration method was optimized by systematic investigation and the 2D- and 3D calibration techniques were compared. Another feature is the determination of confidence limits of the 3D calibration. This calibration error was calculated by the statistical bootstrap method. The results of calibration experiments and the precision and accuracy of the determination of trace elements in CRMs show that 3D calibration becomes increasingly essential as the refractory character of the analyte increases. Although there are large differences between the state of development and technical performance of the instruments used, 3D-calibration works with both SS-GF-AAS spectrometers.     

Direct ZAAS analysis of solid samples: Early development

Summary Early application of the Zeeman effect to correct for background absorption in atomic absorption analysis is described. This paper also describes the use of this technique for direct analysis of biological samples and the future developments that are expected to occur in this field.

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Direkte ZAAS-Analyse von Feststoffen: anfängliche Entwicklung

Zusammenfassung Es wird über die ersten Anwendungen des Zeeman-Effektes zur Untergrundkorrektur in der AAS berichtet. Der Nutzen dieses Verfahrens für die direkte Analyse von biologischen Proben sowie mögliche zukünftige Weiterentwicklungen werden ebenfalls diskutiert.

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Lecture given at the colloquium on the Analysis of Solids by AAS, Wetzlar, 8.–10.10.1984     

Direct solid sample analysis using pressure regulated electrothermal atomization with atomic absorption spectrometry

Summary The elements Ag, Cd, Cu, and V in coal fly ash have been analyzed directly using pressure regulated electrothermal atomization with atomic absorption spectrometry with a relative standard deviation of about 10%. One to four mg of fly ash were added directly to the furnace. A small amount of water was added on top of the sample before drying to prevent expulsion of the very fine particles during chamber evacuation. The methodologies have been verified using standard coal fly-ash (NIST 1633a), and results within the certified concentration range have been obtained. Standard curves from aqueous solutions can be used for the determination of volatile and moderately volatile elements, while the standard additions method was needed for refractory elements due to the analyte expulsion by the fly ash matrix.Presented at the 5th International Colloquium on Solid Sampling, with Atomic Spectroscopy, May 18–20, 1992; Geel, Belgium. Papers edited by R.F.M. Herber, Amsterdam     

Direct introduction of solid samples into continuous-flow systems by use of ultrasonic irradiation

A new approach to the on-line treatment of solid samples based on the use of flow-injection analysis and acceleration of the partial dissolution (leaching) of the sample by using ultrasonic irradiation is proposed. Selection of a suitable leaching agent makes possible the solubilization of the component(s) of interest. This approach was applied to the determination of iron in plant material by acid dissolution followed by complex formation with 1,10-phenanthro- line. The results obtained are in agreement with those found by the conventional method using atomic absorption spectrometry after hot-acid treatment.     

Quantitative headspace analysis of solid samples; a classification of various sample types

Summary Volatile compounds in various solid samples have been analyzed quantitatively by equilibrium headspace gas chromatography with the technique of multiple headspace extraction (MHE). Solid samples can represent either a partition system, such as certain polymers, or an adsorption system, particularly when present as porous material. It has been found that the humidity of the sample has a strong influence on the equilibration in an adsorption system with a hydrophilic matrix and that the addition of water increases the volatility and speeds up the equilibration time. The influence of various important parameters, such as temperature, time, size and structure of the solid samples on the equilibration is demonstrated on the examples of the quantitative determination of vinyl chloride monomer in PVC, styrene in polystyrene, ethylene in polyethylene, ethylene oxide in a contact lens, halogenated hydrocarbons in coffee and residual solvents in drugs. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Direct solid sample analysis of SiC-powders by DC glow discharge and DC-ARC emission spectroscopy

Glow discharge atomic emission spectroscopy (GD-OES) and the classical spectrographic method with a dc arc source (DC-ARC OES) have been applied to the direct analysis of SiC powders. The homogeneity of pellets prepared from mixtures of SiC with copper powder and used for the GD experiments was investigated in detail. Various methods have been tested for the analytical calibration. These have been applied to the direct solid sample analysis of technical SiC powders. The experimental data were evaluated by chemometrical procedures. The results of the two methods have been compared.     

Deuteron activation analysis of geological samples

Deuteron activation was found to be suitable for analysing geological samples, as no interfering activities are formed from oxygen, silicon and aluminium, which together make up more than 80% by weight of the earth's crust. To test the applicability of this method to geological samples, the mineral tourmaline was activated with 5.5 MeV deuterons obtained from the 6 MV van de Graaff accelerator at the Southern Universities Nuclear Institute. The induced activities were measured and analysed by gammaray spectrometry and the elements Al, Mg, B, Mn, Na, Fe and Li could readily be determined.     

Methods of calibration in the direct analysis of solid samples by electrothermal atomic absorption spectrometry

One of the major problems involved in the direct analysis of solid samples by electrothermal atomic absorption spectrometry (ETAAS) lies in the calibration step because non-spectral interference effects are often pronounced. Three standardization techniques have been described and used in solid sampling-ETAAS: (i) standard additions method; (ii) calibration relative to a certified reference material; and (iii) calibration curve technique. However, an adequate statistical evaluation of the uncertainty in the analyte concentration in the solid sample is most frequently neglected, and reported errors may be seriously underestimated. This can be attributed directly to the complexity of the statistical expressions required to accurately account for errors in each of the calibration techniques mentioned above, and the general lack of relevant reference literature. The object of this work has been to develop a computer package which will perform the necessary statistical analyses of solid sampling-ETAAS data; the result is the program “SOLIDS” described here in the form of an electronic publication in Spectrochimica Acta Electronica, the electronic section of Spectrochimica Acta Part B. The program could also be useful in other analytical fields where similar calibration methods are used. The hard copy text, outlining the calibration models and their associated errors, is accompanied by a diskette containing the program, some data files, and a manual. Use of the program is exemplified in the text, with some of the data files discussed included on the diskette which, together with the manual, should enable the reader to become familiarized with the operation of the program, and the results generated.     

A review on molybdenum determination in solid geological samples

This review highlights the necessity for the development of proper sampling and storage, fast pretreatment methodology followed by highly sensitive detection for the determination of molybdenum in geological samples. Distribution of concentration and chemical speciation of molybdenum analysis in solid geological matrices have also been discussed.     

Direct solid sample analysis of sediments, soils, rocks and advanced ceramics by ETV-ICP-AES and GF-AAS

Methods for the direct solid sample trace element determination in complex composed inorganic powder samples, e.g. sediments, soils, rocks, minerals and similar technical materials, are systematically investigated by SS-ETV-ICP-AES and SS-GF-AAS. High-grade homogeneity of the sample powder even at milligram and sub-milligram levels is required due to small sample weights. All the investigations are carried out with CRMs and RMs. SS-ETV-ICP-AES, which has been improved by high temperature vapor halogenation, is used for the determination of Cr, Cu, Ni, Pb, and Zn in the trace element range < 10 to > 500 μg/g. No significant influence of matrix components is observed using this method. SS-GF-AAS is used for the determination of Cd, Pb, and Zn in the 0.006 to 150 μg/g range. Precision and accuracy of SS-GF-AAS are improved by application of 3D-calibration plots in comparison to conventional 2D-calibration. In this way, the two methods SS-ETV-ICP-AES and SS-GF-AAS complement one another concerning their analytical performance.     

Direct solid sample analysis of sediments, soils, rocks and advanced ceramics by ETV-ICP-AES and GF-AAS

Methods for the direct solid sample trace element determination in complex composed inorganic powder samples, e.g. sediments, soils, rocks, minerals and similar technical materials, are systematically investigated by SS-ETV-ICP-AES and SS-GF-AAS. High-grade homogeneity of the sample powder even at milligram and sub-milligram levels is required due to small sample weights. All the investigations are carried out with CRMs and RMs. SS-ETV-ICP-AES, which has been improved by high temperature vapor halogenation, is used for the determination of Cr, Cu, Ni, Pb, and Zn in the trace element range < 10 to > 500 μg/g. No significant influence of matrix components is observed using this method. SS-GF-AAS is used for the determination of Cd, Pb, and Zn in the 0.006 to 150 μg/g range. Precision and accuracy of SS-GF-AAS are improved by application of 3D-calibration plots in comparison to conventional 2D-calibration. In this way, the two methods SS-ETV-ICP-AES and SS-GF-AAS complement one another concerning their analytical performance. Received: 6 April 1999 / Revised: 3 August 1999 / Accepted: 4 August 1999     

An automated solid sample analysis system

Summary An automated solid sampling analysis system (SSAS) consisting of a powder sampler, an integrated microbalance, a transport and handling system for the sample boat, a microcontrolling unit for all necessary steps and an appropriate AAS instrument is described in detail and its potential for routine metal determination in various materials is demonstrated.     

The use of direct electron excitation for the analysis of geological samples and comparison of this technique with X-ray fluorescence

A method for the analysis of geological samples has been developed and a study has been made of the methods of sample preparation. These consist of mixing of the sample with graphite for electrical conduction or the evaporation of a conducting layer onto the disc. An investigation has been made to find the best sample/graphite ratio as well as to measure the influence of the evaporated layer on radiation intensity of the elements. Other parameters of importance such as electron accelerating voltage, absorbed electron current, etc. have also been investigated. Analytical calibration curves for heavy and light elements are shown. X-ray fluorescence and primary X-ray direct electron excitation have been compared with respect to mass absorption, sensitivity and detection limits.     

Determination of silver in irons and steels by atomic-absorption spectrometry with an induction furnace: Direct analysis of solid samples

The silver contents of 17 irons and steels have been determined by dropping 0.5-20mg of millings or turnings of the metals into an induction furnace situated within an atomic-absorption spectrophotometer. The limit of detection was 0.005 mug/g and the relative standard deviations were 12% or better for silver contents of not less than 0.05 mug/g. Samples are added to the furnace at 4-5 min intervals.     

Direct analysis of solid samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer and D2-background correction system (SS GF-AAS)

An instrumental design for the analysis of heavy metals in solid samples (certified reference materials, river sediments, cements) by direct graphite furnace atomic absorption spectroscopy (SSGF-AAS) is presented and outlined. A high performance atomic absorption spectrometer with a D₂-background corrector and a transversely heated graphite atomizer was modified. Solid sampling was achieved by a mechanical module combined with an ultra microbalance. Cadmium, lead and chromium in different samples (sample weights between 20–400 μg) have been determined in the μg/g- to ng/g-range with the graphite-platform technique. Different ways of calibration and inhomogeneity problems are discussed. The precision of SSGF-AAS is equal to the precision of the conventional AAS-technique with chemical digestion (microwave digestion system, Zeeman-AAS). It is shown that SSGF-AAS is a reasonable alternative to the conventional technique for selected analytical problems.     

Direct analysis of solid samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer and D2-background correction system (SS GF-AAS)

An instrumental design for the analysis of heavy metals in solid samples (certified reference materials, river sediments, cements) by direct graphite furnace atomic absorption spectroscopy (SSGF-AAS) is presented and outlined. A high performance atomic absorption spectrometer with a D₂-background corrector and a transversely heated graphite atomizer was modified. Solid sampling was achieved by a mechanical module combined with an ultra microbalance. Cadmium, lead and chromium in different samples (sample weights between 20–400 μg) have been determined in the μg/g- to ng/g-range with the graphite-platform technique. Different ways of calibration and inhomogeneity problems are discussed. The precision of SSGF-AAS is equal to the precision of the conventional AAS-technique with chemical digestion (microwave digestion system, Zeeman-AAS). It is shown that SSGF-AAS is a reasonable alternative to the conventional technique for selected analytical problems. Received: 19 February 1997 / Revised: 30 May 1997 / Accepted: 4 June 1997     

Direct atomic-absorption spectrometric analysis of geological materials-a review

A review is given of the problems likely to be encountered in the atomization of solid samples of geological materials, and of the applications of this technique.     

241Am-XRF analysis of rare earths in geological samples

Rare earths in sediments are analyzed by X-ray fluorescence using²⁴¹Am as an excitation source. The analytical sensitivity lies in the ppm range.     

Matrix sensitivity of solid sampling AAS. Determination of zinc in geological samples

Direct solid sampling techniques in AAS have several advantages over wet digestion methods such as small sample size requirements and simple calibration procedures. But some disadvantages also exist such as the sample in homogeneity and the matrix sensitivity of calibration. The calibration is commonly carried out by varying the sample mass and evaluating the peak intensity versus absolute analyte amount. It is shown here that this procedure must be considered doubtful when matrix effects are expected. In the case of zinc determination in geological samples it has been shown that calibration functions obtained by different reference materials differ significantly from each other. As an alternative a three-dimensional calibration technique can be applied that evaluates the peak intensity versus both analyte content and sample weight. The resulting calibration planes are expected to be hyperbolically curved. This three-dimensional calibration has been applied to the determination of Zn in geological samples and compared with classical solid sampling AAS calibration procedures.