Topic summary

"Greater than or equal to 99%" as a specification rather than a result

Analytics › COA interpretation reference standards documentation quality batch & lot numbers amino acid analysis Solved

This is a generated summary. It shows the 9 most-liked posts from a topic of 147, 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.

SHermansenTL2Member Solution9 Jul 2025#5

On the opening post — agreed on the reasoning, with one qualification.

Counter-ion form is crucial: peptides are isolated as salts, most often trifluoroacetate from reversed-phase purification or acetate after salt exchange. The counter-ion is part of the mass in the vial and is not part of the peptide. Two vials of the same purity, one as TFA and one as acetate, contain different amounts of peptide per milligram.

8 likes 13mo

b.fonsecaTL2 Moderator17 Aug 2025#21

Sterility testing is separate: chromatographic purity, mass spectrometry, and endotoxin testing all say nothing about whether a solution is sterile. If sterility matters, it needs to be tested and reported.

31 likes 11mo

lc_gradientTL3Analytical chemist4 Sep 2025#30

post #29 is right about the mechanism and I think understates the practical bit.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

30 likes 11mo

a.iyerTL2 Moderator14 Sep 2025 · edited#35

Reading old certificates: if a certificate is dated years ago, the lot it describes might be old. That is not automatically a problem but it is worth noting. Fresh testing on the current lot is stronger than old testing on an older lot.

33 likes 10mo

r.vukovicTL2 Moderator7 Oct 2025#48

32 likes 10mo

r.chukwuTL2 Moderator17 Nov 2025#72

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

31 likes 8mo

n.cabreraTL2 Moderator15 Dec 2025#90

This follows post #87 rather than contradicting it.

When method identifiers are missing: "reversed-phase HPLC" is less specific than "reversed-phase HPLC at 214 nm on a C18 column with a 10 to 40% acetonitrile gradient over 20 minutes". The second lets someone reproduce the analysis. The first does not.

33 likes 7mo

o.abrahamsenTL3Regular31 Jan 2026#122

stopper_shift, post #92: On post #88 — agreed on the reasoning, with one qualification. When a document puts the specification in the result column, it has told you the release criterion, not the measurement. Those are different claims and the second is weaker. Go to post

What fields matter on a certificate: lot number matching the vial, test date, the analytical method stated specifically, the measured result as a number, and the acceptance limit stated separately. A certificate missing any of these is weaker.

31 likes in reply to #92 6mo

i.amankwahTL2 Moderator23 Feb 2026#138

Endotoxin testing is separate: a certificate of purity says nothing about endotoxin. A chemically pure preparation can carry a clinically significant endotoxin load. If endotoxin matters, it needs to be tested and reported.

29 likes 5mo

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This topic was referenced in

[2026 update] A certificate with no method stated: what can you conclude?Analytics › COA interpretation · 2 replies
Counter-ion form: the field almost nobody reports — one year onAnalytics › COA interpretation · 139 replies

Promoted into the documentation commons. The content of this topic is maintained at Amino acid analysis for peptide content, with named maintainers and a review date. The promotion was discussed in doc review. Corrections are best raised against the document, which is the version that gets kept current.

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