Concretely: MKM · survodutide.
I have the document in front of me and I can read the numbers. What I cannot do is interpret them.
I am reasonably comfortable with statistics and completely uncomfortable with chromatography, or vice versa.
Which parts of this are informative and which are decoration?
Acetate is generally preferred to trifluoroacetate for biological work, which is why the exchange is done at all.
Peptides purified by reverse-phase chromatography with a trifluoroacetic acid mobile phase are isolated as trifluoroacetate salts. The trifluoroacetate content depends on the number of basic residues and can run from a few per cent to well over ten by mass on a heavily basic sequence.
| Component | Typical share | Counted in purity? | Counted in content? |
|---|---|---|---|
| Target peptide | 88–94 % | Yes, as main peak | Yes |
| Related impurities | 1–3 % | Yes, as other peaks | No |
| Counter-ion (TFA or acetate) | 2–8 % | No | No |
| Residual water | 2–6 % | No | No |
| Bulking agent, if present | 0–40 % | No | No |
Acetate salts are produced by a deliberate ion exchange after purification. The exchange costs a processing step and is the reason acetate-form material is more expensive.
Ion chromatography and fluorine NMR are the accepted quantitative methods for trifluoroacetate, and neither is a chromatographic purity method.
Ask for net peptide content. It folds water and counter-ion into one usable number.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemThe honest answer is that most certificates are silent on it and that the number can be large enough to matter.
Quantification differs by ion: trifluoroacetate by ion chromatography or by fluorine nuclear magnetic resonance, acetate by ion chromatography or by capillary electrophoresis. Neither shows up on a UV chromatogram.
Worth being precise here: net peptide content — the fraction of gross mass that is the peptide itself — is the figure that folds water and counter-ion together and is what you should ask for if you ask for anything.
The caveat is that a purity figure is completely blind to counter-ion content, and the two are routinely conflated.
Trifluoroacetate unless a deliberate exchange was done. Ask which.
The relevant arithmetic is that gross mass equals peptide plus counter-ion plus water, and the certificate usually reports only the first indirectly.
Trifluoroacetate has documented biological effects at higher concentrations in cell culture, which is the technical reason acetate exchange exists rather than a marketing one.
On the detail: a supplier who reports both water and counter-ion has given you everything needed to reconcile the vial, and on this site that is a very short list.
Trifluoroacetate effects in cell culture are documented and are the technical basis for salt exchange to acetate.
Count the basic residues and you can estimate the counter-ion load.
edited 21 Jan 2025 by priya_menon — removed a claim I could not source
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.