Reading a chromatogram someone posted without axes — setting out what I have, and where I think it stops being reliable.
Posting a small dataset on reading a chromatogram. It is mine, it is uncontrolled, and the method is stated so it can be discounted appropriately.
What I would like is not agreement but a second dataset collected by someone with no stake in mine. If one exists I would rather read it than argue for this one.
Confirming post #7 from a second method, which matters more than confirming it from a second person.
System suitability testing: injections run before and during the sample run to establish whether the instrument, column and method were performing when the sample was analysed. If suitability did not pass, the sample results from that run are uninterpretable.
Following this. I have the same question and no better information than the first post.
Injection volume matters because column overload distorts peak shape, and an overloaded main peak can swallow a small neighbour. A certificate without injection volume is missing something load-bearing.
Right — I had this wrong and I am glad to have read it before it mattered.
Picking up post #46: that is the part I would want checked first.
Gradient delay volume differs between instruments and shifts the whole chromatogram. It is why a transferred method rarely reproduces retention times exactly on a different system.
My understanding of reading a chromatogram is a few years old and may have been superseded. If it has been, I would genuinely like to know rather than keep repeating it.
Gradient slope is the single biggest driver of apparent purity differences. A shallower gradient over a longer run resolves more impurities and gives a higher purity figure. A steep gradient produces a tidier-looking chromatogram with fewer visible peaks and gives a lower purity figure. Both are legitimate methods and they will not produce the same number.
The number is defensible. The precision I gave it is not.
Read the full topic (56 posts)
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Why I ask for the gradient before I discuss the number
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Coming back to: Column chemistry choices for a 40-residue peptide
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Column chemistry choices for a 40-residue peptide
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What a reversed-phase purity number actually is — the long version
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Area percent versus weight percent: the confusion that causes most arguments
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Follow-up: Attributing a new peak: degradation product or excipient?
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+15 | 19 | 671 | 17mo |
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Injection volume, overload, and peak distortion — one year on
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