Linearity of imps in the presence of main peak - rationale?

[Rob Burgess]

One of our SOP's states that it should be done this way. I'm not sure I understand the rationale for this - the impurity peak is very well separated from the main peak so why do in the presence of it?

I presume it might have consequnces for extraction issues - am I on the right lines here? Even so I figure the risk would be negligible in most cases.

[Peter Apps]

At a guess I would say that it is order to validate the method under conditions as close to actual practise as possible - there are lots of analyses that look lovely with nice clean standards, and very ugly with real samples.

Peter