Proficiency tests

[Ryklys]

Hello, coleagues,

reasenty I came up to a problem I can't solve myself. Our lab participated in the PT (benzo(a)pyrene in smoked food). Just when the test arrive I did a sertificated material test (made by the same company, that provided the PT). The results complied with the serticicate. But my PT result was 2.2 time higher than it should be. The sample matrixes were quite similar — smoked fish and smoked meat. I din't notice any mishappenings during sample preparation. Preparation reactives were all the same from the same batch actually.

Questions:

1 Anyone ever had any doubts about Proficiency test results?
2 Any issues with FAPAS ever?
3 Any thoughts what could have happened?

Thank you in advance.

[richiekichi]

Was this the final result issued by FAPAS or just the interim report? Wait till you get the final report. The assigned value is based on all the results from all participating laboratories around the world.

If you have any of the PT material, try testing it again. If you always fail this PT then you have problems but if you get an outlier once in awhile it could just be down to a preparation error. Standards past their best, pipettes or balances having a bad day. The possible causes are endless.

[Ryklys]

Thank you richiekichi,

thing is I used almost all material — did a follow up assey. (So not mutch left really.) And got really simillar result. As for standarts. We use two different standarts solutions prepared from two different stocks in one assey. (Produced by different suplyers.) Just to be sure.
We have the final report. And I noticed strange dispersion of the results. Kind of groups with quite simillar results from the labs with quite simillar bib numbers. I kind of wanted to know if rubish happens to the PT supplyers as well or it is just our end always...