An example of IS response. Need your helps. [Bioanalytics]

posted by Sukalpa Biswas – India, 2020-05-26 13:49 (761 d 02:28 ago) – Posting: # 21471
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(edited by Sukalpa Biswas on 2020-05-26 14:05)

» [image]

Clearly from that graph the instrument response has been increased gradually over a period of time. I think the acceptance criteria is +/- 25% of the IS response of the average of accepted CC and QC. The criteria fulfilled because the response of IS in CC and QC increased along with study samples, as per SOP.
There might be many reasons behind the enhancement of the response of IS,
  1. System may not stabilized while submitting the batch.
  2. May be column is not saturated enough.
  3. May be the category of the molecule require more stability runs to stabilize. etc.
But there is always a possibility to investigate the reason of the enhancement of the response of IS. The particular batch can be repeated under investigation with proper documentation.
But personally speaking, I have come across this type of scenarios in the past. But possibilities of the change in concentrations are less, because we determine concentrations based on the area ratio. Looking at the data, I think the response of IS and analyte increased proportionally as the QC samples are passed resulting a successful analytical run.

Edit: Full quote removed. Please delete everything from the text of the original poster which is not necessary in understanding your answer; see also this post #5[Helmut]

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