Filtern
Dokumenttyp
Sprache
- Englisch (3)
Referierte Publikation
- ja (3)
Schlagworte
- EDX (3)
- EPMA (3)
- WDX (3)
- CCQM (2)
- Cu-Au alloy (1)
- Interlaboratory comparison (1)
- K-values (1)
- Metrology (1)
- Pilot study (1)
- Quantification (1)
CCQM (Consultative Committee for Amount of Substance - Metrology in Chemistry) is an international body of the Meter Convention (BIPM) established as a framework of National Metrology Institutes running inter-laboratory of comparisons to demonstrate the international comparability of chemical measurements, with traceability to international or national reference standards. In 2003 the surface analysis working group (SAWG) was established at CCQM and since then several inter-laboratory comparisons in the field of EPMA have been carried out. In many cases the EPMA results deviated significantly from each other and the expanded uncertainties were greater than expected. Both methods EDS and WDS were employed. However, light elements such as carbon and nitrogen were the major elements analyzed and it is known that the corresponding lowenergy characteristic X-ray lines are more challenging to quantify by EPMA than the higher energy lines of elements with higher atomic numbers. Moreover, the standards selected and their qualities were variable, the quantification models were different, and the acquisition parameters were not specified sufficiently in the analysis instructions.
An inter-laboratory comparison organized as a pilot study (PS) has been performed under the umbrella of the Consultative Committee for Amount of Substance – Metrology in Chemistry (CCQM) / Surface Analysis Working Group (SAWG) with the objective to compare k-values measured with Electron Probe X-ray Microanalysis (EPMA) for copper-gold alloys. The k-value, defined as the ratio of the Xray photon intensity of an X-ray characteristic line of the unknown sample to the corresponding one in the reference material, is a rough estimate of the mass fraction of the respective element. Basically, the mass fractions can be calculated from the k-values after applying a matrix correction procedure, which includes empirical approaches, so that traceability gets lost. Due to its physical, measurable nature, the k-value has been selected in the present PS as the primary measurand. The mass fraction has been set as the secondary (derived) measurand. Both EDX and WDX have been employed. The WDX results and the overall comparability between the k-values obtained by EDX and WDX are still in progress.
Standardization and metrology are two terms which are used rather rarely at major conferences as well as in scientific publications in the field of microbeam analysis. For laboratories operating under an accreditation scheme the operator of the microscope/microprobe must have available internal, national or international written standards which should be applicable to any quantitative analysis. Hence, requirements, specifications, guidelines or characteristics of methods, instruments or samples are provided with the final goal that these can be used consistently. In this way it is ensured that microbeam analyses results are reliable and meet quality-management requirements.