Varying Peak Heights and Areas

[Cindy]

We have been experiencing some variability in peak height and area for dissolution samples over the last few weeks. When samples are re-injected the next day, the values return to expected range (i.e. 100%). We are investigating whether the issue may be related to the dissolution apparatus or sampling technique, but we have not ruled out HPLC issues. either. Is there any possibility that the variability may be caused by electrical surges - we have had reduced power usage in this area over the last couple of weeks and were grasping at straws thinking it may be the issue. The variability has been seen with several methods, in a couple of labs on a variety of HPLCs.

Any thoughts?

[tom jupille]

If your chromatograms have more than one peak, try looking at the ratios of peak areas (or heights) for a couple of peaks. If there is less variability (%RSD) in the ratios than in the individual values, that suggests that the problem occurred when the peaks were still together (i.e., sampling, dissolution, or injection).

While I suppose it's not impossible, I find it hard to visualize a mechanism whereby peak sizes would be more variable if the line voltage drops a bit.