We currently analyse plasma protein products for molecular weight profile by GPC. As with all our other assays we use a product (IgG or Albumin) as a control and assign limits to the amount of one or more of the eluted peaks. As the column 'ages' the values (% area) of these peaks continually rises or falls dependant on which we use, and, therefore does not meet the 'classic' variation around the mean.
It has been suggested that we use one of these products to set limits using the plate count and asymmetry measurements of one of the peaks. (The largest peak in one of our products (IgG) does not exhibit baseline resolution.)
Can anyone give me some clues as to the best way to set a limit this way esp. to meet FDA regs? Our other chromatography assays are relatively easy thanks to baseline resolution, it's just this one.

Apologies for the long post
John Preece