Reading back through, this was answered upthread and I missed it. My fault.
4 likes 12mo
Topic summary
Reconciling a label claim with a content assay
This is a generated summary. It shows the 5 most-liked posts from a topic of 7, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.
Water content (residual moisture) matters: lyophilised peptide is not dry. A few percent water is normal. The difference between a TFA salt and an acetate salt can be several percent. Content calculations need the water content to be accurate.
12 likes 10mo
Purity and content are different measurements: purity tells you what proportion of the detected material is the intended species. Content tells you how much of the intended species is present in the container. A lyophilised vial can be 99% pure and contain considerably less than the label claims because the remainder is water, counter-ion and excipient.
26 likes 8mo
I read post #4 twice before replying, because I had assumed the opposite.
Amino acid analysis gives content: it hydrolyses the peptide and quantifies the residues. It measures the peptide content independent of chromatographic purity. Very few supplier certificates report it.
Stating my assumptions rather than smuggling them in.
7 likes 6mo
Purity and content are different measurements: purity tells you what proportion of the detected material is the intended species. Content tells you how much of the intended species is present in the container. A lyophilised vial can be 99% pure and contain considerably less than the label claims because the remainder is water, counter-ion and excipient.
The right answer here may simply be that it has not been measured.
18 likes 4mo
This topic was referenced in
- A certificate with no method stated: what can you conclude?Analytics › COA interpretation · 57 replies
- "Greater than or equal to 99%" as a specification rather than a resultAnalytics › COA interpretation · 146 replies
- Which fields on a certificate actually matter, rankedAnalytics › COA interpretation · 29 replies
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