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- Proficiency testing (PT) (2)
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- Reference materials (RM) (2)
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Eingeladener Vortrag
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Abstract The use of proficiency testing schemes (PTS) by laboratories as an integral part of their quality
system has been increasing in recent years. Accreditation bodies, regulators and the laboratories customers
are increasingly using results from PTS in their relationship with laboratories. There are many PTS available in
Europe in analytical chemistry; EPTIS indicates over 400. The comparability of these PTS is now a real issue,
as many organisers of PTS move into new markets. The COEPT project has systematically demonstrated (in four
technical sectors water, soil, food and occupational hygiene), that there are many similarities between PTS in
each sector. For example, nearly all use the z-score as a performance index. One significant difference between
many PTS is the value used for the term s in the z-score equation, and this gives a range of evaluations for the
same data point. Despite this, the agreement between PTS in the same sector for the evaluation of data is
approximately 85%. COEPT has given us a basis for establishing the comparability of PTS and showing us where
further harmonisation could occur.
Recently, the International Measurement Evaluation Programme (IMEP) organized an interlaboratory comparison on total concentrations of eight polycyclic aromatic hydrocarbons (PAHs) in natural inland waters. It was carried out in support to the European Union Water Framework Directive (EU-WFD) that lists these eight as priority substances.
As sample matrix, we used groundwater spiked with humic acid as a model for the colloidal substances that are present in natural inland waters. Humic substances can adsorb PAHs, but we found that some laboratories did not apply analytical procedures that sufficiently accounted for this. One of these laboratories was involved in establishing the reference values. We show how this impacted on the reliability of their measurements.
Many participants accepted our invitation to report their measurement uncertainties. We assessed their results against our reference values and uncertainties, and provided z and zeta scores. Although the overall measurement capability appears satisfactory, there is room for improvement of analytical procedures as regards the use of measurement standards.
The International Measurement Evaluation Program (IMEP) organized the IMEP-24 interlaboratory comparison after reports in the media about high levels of lead in toys. The aim of this comparison was to verify the laboratories' capacity to evaluate trace-element levels in a possible toy-like material according to the European Standard EN 71-3:1994. As test material, it used a former certified reference material containing levels of antimony, arsenic, barium, cadmium, chromium, mercury, lead and selenium around the limits set in the standard.
Four expert laboratories confirmed the reference values (Xref) for all elements but Hg, and established a reference value for Hg. The scatter of the results reported by the participants was large, as expected, but showed a close to normal distribution around the reference values for five of the eight trace elements. The spread of results was mainly attributed to sampling and sample preparation.
One major issue observed in this exercise was the lack of legislative rules about how to report the result, or, more specifically, the use of the analytical correction, which was introduced in EN 71-3:1994 to achieve consistent interpretation of results and which is to be applied when values are equal to or above the maximum limits set in the standard. Its application by the participants was very inconsistent and led to problems in their evaluation. There is clearly a need for clarification and for more formal regulations with regard to result reporting in order to minimize the risk of confusion.
Participants were also asked to give their opinion with regard to the acceptability of the test material for the market. The majority correctly considered the material as non-compliant. However, almost one-third incorrectly assessed the material as compliant.
EPTIS update
(2003)
EPTIS for Latin America
(2004)
DIN EN ISO/IEC 17043:2010 Konformitätsbewertung - Allgemeine Anforderungen an Eigungsprüfungen
(2012)
EPTIS
(2013)
EPTIS
(2015)
Im Vortag werden die aktuellen Arbeiten und Ergebnisse zum PT-Projekt "PAH in toys rubber" vorgestellt. Der PT, organisiert und ausgerichtet von BAM-1.7, erfolgt im Rahmen der deutsch-chinesischen Arbeitsgruppe "Produktsicherheit" (BMWi/AQSIQ). Ziel des PT ist es, die Messfähigkeiten deutscher und chinesischer Laboratorien bzgl. PAK in Spielzeugprodukten zu bewerten. Hintergrund sind neue PAK-Grenzwerte für Verbraucherprodukte und Spielzeug seit 27.12.2015 (EU-Verordnung 1272/2013). Neben der Herstellung und Charakterisierung des "PAK in Gummi" Referenzmaterials werden im Vortrag die Labor-Ergebnisse vorgestellt, die statistische Auswertung präsentiert und eine erste Bewertung der verwendeten Analysenverfahren vorgenommen.
Current developments in PT
(2021)
COMAR, where do you go?
(2018)
Currently BAM is making efforts to recode COMAR, the database for CRMs and reshape its profile as a database intended for qualitatively top-of-the-market CRMs. These efforts are highlighted and placed into the broad perspective of the international RM markets. A link to EPTIS, the database for PT schemes as a blueprint for the recoding is provided.