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Topic: Why usually six replicates?  (Read 3626 times)

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Offline rasl

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Why usually six replicates?
« on: November 22, 2010, 09:25:57 AM »
Hi ,
I wonder why "six" is the most usual number of replicates in analytical chemistry, to linear calibration or to get the repeatability Why not just five, for example?
Thanks for your answers.

Offline Stepan

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Re: Why usually six replicates?
« Reply #1 on: November 22, 2010, 09:59:37 AM »
It is likely depends on industry. EPA likes "7 replicates to measure MDL", NIOSH wants "5 point calibration", "2 points for recovery", and "2 blanks".

Offline rasl

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Re: Why usually six replicates?
« Reply #2 on: November 22, 2010, 10:11:21 AM »
Thanks for your answer.

Yes, you are right. depending on the Protocol a number of replicates should be selected (IUPAC, ISO, etc). But in some cases, such as in some in-house validation, or just to check repeatability, in some papers I saw several times this "six replicates" without any reference to a protocol. Maybe it is just a habit? Or maybe is just inherent and they dont explain it.

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