Hi
we are currently tranfering a method from another site. first I have to specified that we do not change anything except the ratio of mobile phase to optimse the peak separation. All the rest is the same.
The fist analyst did 6 analysis on one lot containing the three components and obtain a good rsd for all of them (less than 2.0%).
He reanalyse the same lot
3times on a different day and the rsd remains low.
When the other analyst try to make 6 analysis of the same lot only one component in one preparation gave anormal result (114%)instead of 105%. this gave a rsd on 6 of 3.4%.
We can not suspected the analyst since he make 6 analysis on another lot in the same run and every thing was fine.
The product is prepare by weihting the lotion directly into the flask and then complete whith diluent.
what can we suspected first.
all the standard are good and the chromatography shows no evidence of new peaks.
thanks

Since it is only one component which is giving you trouble, I would suggest that there was possibly a problem with the weighing of that component for the standard.

I would repeat the analysis of those same sample preparations (assuming they are stable) with a freshly prepared standard.