Variation in the retention timein different day analysis

[sanjivsharma]

Can any one suggest me how much variation in retention time is acceptable between different day analysis? Suppose today we have analyzed a product and main peak elutes at 10 minute. So when we analyze this product on different day say after one month, how much variation in retention time is acceptable? If there is any guideline then please inform.

Thanks

[tom jupille]

In principle, any time window is OK so long as you meet specificity requirements (i.e., no other compounds eluting within that time window).

[sksharma]

As a general rule we are using a criteria of +/- 10%, from the retention time specified in the respective STP, if the retention time window is not specified in the STP.