Brackating standards

Hi everyone
Suppose my hplc sequence is as follow
Std. 6
Brakating standerd 1
Sample 2
Brackating standard 2
Then how to calculate %RSD for second bracketing standards whether it is 6+1+2 or 6+2
Also need referance guideline

Generally Bracketing standard is placed only after all the samples are put in sequence, unless there are many samples to be injected. May be after 5 to 6 samples.
% RSD of the Braketing standard should be calculated considering 5 or 6 standard injections plus the Bracketing standard. This %RSD limit is usually 1% more than the % RSD limit of 5 or 6 standard injections.
There should be an internal SOP to include the above aspects.

Thanks sir for your reply
So from your reply i understood that we need to be define it in our internal SOP. There is no any referance available.

Please refer WHO Guideline on Good Chromatography Practice (Annex-4, WHO- 54th report of the year 2020) which is enclosed here for reference.

Acceptance criteria should be set for the SST, bracketing standards, deviation from relative retention and any other aspect that may be deemed necessary for the chromatographic analysis. This includes
acceptability of peak shapes.

Bracketing standards (standard solution injections) should be included in the sample set, at defined intervals, where appropriate. The number of bracketing standards included in a sample set should be defined. Compliance with the defined acceptance criteria should be verified.

WHO TRS 1025-annex 4_Good Chromatography Practice.pdf (121.3 KB)

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