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- 2019 (2) (entfernen)
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- Englisch (2)
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- CCQM (1)
- Calibration (1)
- Fast flow GD (1)
- GDMS (1)
- Matrix independent calibration (1)
- Metrology (1)
- SI Traceability (1)
Organisationseinheit der BAM
Within the Working Group on Inorganic Analysis (IAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) international key comparisons and pilot studies related to inorganic analysis are carried to ensure consistency in this field at the highest level. Some of these comparisons deal directly with the preparation and characterization of monoelemental solutions or with topics, closely related. The importance of monoelemental solutions lies in the fact that almost every measurement in inorganic analysis relies on the comparison with either a reference material, or references in form of solutions, usually (mono)elemental solutions. All quantitative measurement approaches, e.g. isotope dilution or standard addition, need an accurate reference solution made from a well characterized reference material, prepared under full gravimetric control. These primary (monoelemental) solutions do not only serve as arbitrary references/calibration solutions, but they also link up measurement results to the International System of units (SI), this way establishing the so-called metrological traceability to a measurement unit of the SI. Without such solutions on the highest possible level of accuracy and with the smallest possible associated uncertainties (for e.g. element content and/or impurities), an analysis itself can never be as good as it could be with appropriate reference solutions. This article highlights select key comparisons and pilot studies dealing with monoelemental solution related topics within the IAWG from the foundation of CCQM – 25 years ago – up to latest achievements in the field of inorganic analysis.
The performance of glow discharge mass spectrometry (GD-MS) is investigated for the accurate quantification of metallic impurities and oxygen in solid samples using the fast flow source GD-MS instrument ELEMENT GD.
Different quantification approaches based on relative and absolute sensitivity factors are evaluated for the determination of metallic impurities using three sample matrixes (Al, Cu and Zn). The effect of the discharge conditions (voltage, current, discharge gas pressure/flow) on the sensitivity is investigated and the parameters are optimized to favour matrix independent calibrations. Improved standard relative sensitivity factors (StdRSFs) are calculated under optimal conditions based on multi-matrix calibrations. The sputtering rate corrected calibration is also presented as a multi-matrix calibration approach.
The capabilities of GD-MS for oxygen determination are also investigated using a set of new conductive samples containing oxygen with mass fractions in the percent range in three different matrices (Al, Mg and Cu) produced by a sintering process. Poor limits of detection (in the order of g/kg) were obtained as consequence of the reduced sensitivity of oxygen in GD-MS and high oxygen background signal intensity as well as its variations. The absolute sensitivity procedure is shown as a matrix-independent approach, which provides quantitative values consistent with those obtained by carrier gas hot extraction (CGHE).