Determination of impurities in solar grade silicon by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) subsequent to matrix evaporation

A method for the determination of 22 trace impurities in solar grade silicon after dissolution in a mixture of HF and HNO3 and subsequent matrix evaporation is reported. The presented method involves a simple, inexpensive, one-vessel sample preparation apparatus design. The recoveries of B, Na, Mg, Al, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Mo, Sb, W, and Tl at 250 μg kg−1 level are in the range of 93 to 108%. After careful selection of monitored isotopes and their respective resolutions, a sector field mass spectrometer has been used to carry out the measurements. Limits of determination down to 120 ng kg−1 have been obtained using a calibration by three-point standard addition. The method was tested on diluted NIST SRM 57b silicon powder as well as on synthetic test samples and also applied successfully on raw solar grade silicon samples in an interlaboratory comparison including NAA

Development of a method based on Instrumental Neutron Activation to determine the homogeneity of trace contaminants in pure substances

The characterization of the highly pure materials used to realize the primary standards in analytical chemistry is important to evaluate correctly the contribution to the measurement uncertainty due to the calibration. In particular, the information concerning the homogeneity of the materials is essential in order to minimize the effect due to sub-sampling. In this framework we developed a method based on neutron activation to estimate the ratio between the fractions of a contaminant element in two samples. The target uncertainty was fixed to 1%. The preliminary results quantified variations of Na, Sc, Nb, Cr, Cs, Zr, Co, Zn, W and Ir in Mg, Mo, Al and Rh. The results concerning Nb in Mo reached the target uncertainty. The uncertainty achieved for the remaining contaminant elements ranged between 3% and 10%.La caratterizzazione dei materiali ultra puri utilizzati per la realizzazione dei campioni primari in chimica analitica è importante per valutare correttamente il contributo all’incertezza di misura dovuto alla calibrazione. In particolare, l’omogeneità dei materiali è fondamentale per minimizzare l’effetto dovuto al campionamento. In questo contesto abbiamo sviluppato un metodo bastato sull’attivazione neutronica per la stima del rapporto tra le frazioni di massa di un elemento contaminante in due campioni. L’incertezza richiesta è stata fissata al 1%. I risultati preliminari hanno quantificato variazioni di Na, Sc, Nb, Cr, Cs, Zr, Co, Zn, W e Ir in Mg, Mo, Al e Rh. I risultati che riguardano Nb in Mo soddisfano l’incertezza richiesta. L’incertezza raggiunta per i rimanenti elementi contaminanti varia tra il 3% e il 10%

Calibration of double focusing Glow Discharge Mass Spectrometry instruments with pin-shaped synthetic standards

Calibration of two commercially available glow discharge double focusing mass spectrometers, the VG 9000 and Element GD, is described using synthetic pin standards pressed from solution doped copper and zinc matrices. A special pressing die was developed for this purpose and optimal results were obtained with the highest possible pressures, i.e., 95 kN\u2022cm - 2. This calibration approach permits the determination of trace element mass fractions down to \u3bcg\u2022kg -1 with small uncertainties and additionally provides traceability of the GD-MS results in the most direct manner to the SI (International System of Units). Results were validated by concurrent measurements of a number of compact copper and zinc certified reference materials. The impact of the sample pin cross-section (circular or square) was investigated with the use of a new pin-sample holder system for the Element GD. The pin-sample holder was designed by the manufacturer for pin-samples having circular cross-section; however, samples with square pin cross-section were also shown to provide acceptable results. Relative Sensitivity Factors for some 50 analytes in copper (VG 9000, Element GD) and zinc matrices (VG 9000) are presented. The field of applicability of GD-MS may be considerably extended via analysis of pin geometry samples based on their ease of preparation, especially with respect to the accuracy and traceability of the results and the enhanced number of analytes which can be reliably calibrated using such samples. \ua9 2011 Elsevier B.V. All rights reserved.Peer reviewed: YesNRC publication: Ye

Use of Instrumental Neutron Activation Analysis to investigate the distribution of trace elements among subsamples of solid materials

none6The results of analytical measurements performed with solid-sampling techniques are affected by the distribution of the analytes within the matrix. The effect becomes significant in the case of determination of trace elements in small subsamples. In this framework we propose a measurement model based on Instrumental Neutron Activation Analysis to determine the relative variability of the amount of an analyte among subsamples of a material. The measurement uncertainty is evaluated and includes the counting statistics, the full-energy gamma peak efficiency and the spatial gradient of the neutron flux at the irradiation position. The data we obtained in a neutron activation experiment and showing the relative variability of As, Au, Ir, Sb and W among subsamples of a highly pure Rh foil are also presented.D'Agostino G; Bergamaschi L; Giordani L; Oddone M; Kipphardt H; Richter SD'Agostino, Giancarlo; Bergamaschi, Luigi; Giordani, L; Oddone, M; Kipphardt, H; Richter, S

Development of a method based on Instrumental Neutron Activation to determine the homogeneity of trace contaminants in pure substances

The characterization of the highly pure materials used to realize the primary standards in analytical chemistry is important to evaluate correctly the contribution to the measurement uncertainty due to the calibration. In particular, the information concerning the homogeneity of the materials is essential in order to minimize the effect due to sub-sampling. In this framework we developed a method based on neutron activation to estimate the ratio between the fractions of a contaminant element in two samples. The target uncertainty was fixed to 1%. The preliminary results quantified variations of Na, Sc, Nb, Cr, Cs, Zr, Co, Zn, W and Ir in Mg, Mo, Al and Rh. The results concerning Nb in Mo reached the target uncertainty. The uncertainty achieved for the remaining contaminant elements ranged between 3% and 10%

Use of Instrumental Neutron Activation Analysis to investigate the distribution of trace elements among subsamples of solid materials

The results of analytical measurements performed with solid-sampling techniques are affected by the distribution of the analytes within the matrix. The effect becomes significant in the case of determination of trace elements in small subsamples. In this framework we propose a measurement model based on Instrumental Neutron Activation Analysis to determine the relative variability of the amount of an analyze among subsamples of a material. The measurement uncertainty is evaluated and includes the counting statistics, the full-energy gamma peak efficiency and the spatial gradient of the neutron flux at the irradiation position. The data we obtained in a neutron activation experiment and showing the relative variability of As, Au, Ir, Sb and W among subsamples of a highly pure Rh foil are also presented

Procedure for the impurity-related correction at the indium fixed-point

Determining the influence of impurities on the fixed-point temperatures of the ITS-90 requires the completion of several tasks. In this paper, the progress made at Physikalisch-Technische Bundesanstalt (PTB) and BAM Federal Institute for Materials Research and Testing is presented and remaining questions are discussed. The projected characterization procedure at PTB, which is based on the established SIE method (sum of the individual estimates), using a new indium fixed-point cell is described as an example. This procedure includes an SI-traceable chemical analysis of the material in the fixed-point cell with sufficiently low uncertainties, the individual experimental determination of the influence of the quantified impurities on the fixed-point temperature, and the establishment of direct links to the phase-transition temperatures of the national standard and of an assumed material of ideal purity. A characteristic difference to the common practice is the chemical analysis of the fixed-point metal being done after determining the cell's freezing temperature. This allows for the detection and consideration of contamination and purification effects due to the filling process, or due to the contact with the carbon crucible and other parts of the fixed-point cell. A chemical analysis of an indium fixed-point was carried out by BAM with relative measurement uncertainties below 30 % which have not been previously achieved. The results provide evidence for the precipitation of some impurities, which is apparently inconsistent with the corresponding binary phase diagrams, but was explained in a recent publication. Implications for the use of the SIE method shall be described briefly at the end. \ua9 2011 Springer Science+Business Media, LLC.Peer reviewed: YesNRC publication: Ye