May be the degree for dried the fruit or nut, missed or smashing the aflatoxin in the fruit or nut.

So, you can dried it under vacuum, before determination the aflatoxin.

We use proficiency test FAPAS. You can check on internet.

Thanks, I need a proficiency test like fapas, but i couldn't find before 15 july 2014. Date is important for me.

you could try with "test veritas - progetto Trieste"

Thank you for your help. There is a avaible test for me, but order deadline has passed. I couldn't order it.

You can use immuno strip test is fast test give you result with 3-5 min

Or if you have standard you can go through TLC method it's semi quantitative methods

have a look at http://fapas.com/proficiency-testing-schemes/

or you try this one: http://www.aokin.com/images/stories/pdf/pf-program2014-en.pdf

and why is the date so critical? if you explain maybe some other solution is possible.

Thanks for your helps. I solved the problem.