Can someone who is familiar with Millenium 32 and PDA detector and FDA inspections of that, give me some advice how to explain in details the results of peak purity in this software.

We know that numbers for purity angle should be below threshold angle and that the curve of purity angle should be below th curve of the threshold +solvent.
But how to explain if the numbers are O.K.,(very close, but below) but the curve of purity angle in sometimes cuts the threshold+solvent curve?

Could we just minimize the injestion volume(the concentration)because the peak if the interest is about 1,0AU ? and say that this is because of the unlinearity of detector?

To define the threshold of the method, do you inject 6 parallel of pure standard once, or you just injected 6 times one solution of standard?

We ask our representatives about all but they don't have enough practice how to explain all details. Waters hadn't answered yet.

Do you have any practice with FDA about the examinations of peak purity?

Defining the right 'noise interval' is the key to getting meaningful peak purity results out of Millennium 32. The Millennium on-line help is actually quite helpful here (for a change).

As I understand it, the 'noise interval' you choose should be the noisiest region of baseline where peaks do not elute. The software uses this information to calculate a realistic solvent threshold.

If your noise interval is not set correctly, noise under a peak will make the peak look impure when it is actually pure. It sounds like this is the problem you are having.

The best way to find your noise interval is to make a few blank injections and get a Maxplot report of your chromatogram. Find the noisiest 1-2 minute interval where peaks do not usually elute, and enter this region in your PDA processing method.

You should also get a Maxplot of your sample and standard chromatograms, and make sure that the peaks are no higher than 1 AU. If they are, reduce your injection volume.

Hope this helps.

In contary to Phill's recommendation, we choose the less noisy baseline in the blank injection.

Please help me. I want to know how we can conclude that a peak of GC chromatogram is pure (contains only one substance)? What is the simply way to check / test the peak purity? I have ever read that we can change the detector, column, temperature and rate flow of carrier gas. But what can we do if we have no other detectors and colums to changed?
Thank you for answer my question.