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%