Trifluoroacetate counterion: difference between revisions
Diff·revision 21 → 22·20:18, 23 Jul 2025
Difference between revision 21 and revision 22 of Trifluoroacetate counterion. 6 lines changed; the page grew by 947 bytes.
| Revision 21 — 13:16, 3 Jul 2025 GastroparesisGwen (talk) add category for method validation 3,918 bytes ±0 | Revision 22 — 20:18, 23 Jul 2025 RetatrutideRuben (talk) ce, tighten prose 4,865 bytes +947 | ||
|---|---|---|---|
| 28 | Nor is it a [[Residual solvent|residual solvent]] in the analytical sense: it is present as a salt rather than as free volatile acid, and a headspace gas-chromatographic method will find little of it. A certificate that reports residual solvents but not counterion has not accounted for this mass.{{r|usp467}} | 28 | Nor is it a [[Residual solvent|residual solvent]] in the analytical sense: it is present as a salt rather than as free volatile acid, and a headspace gas-chromatographic method will find little of it. A certificate that reports residual solvents but not counterion has not accounted for this mass.{{r|usp467}} |
| 29 | 29 | ||
| + | 30 | == Practical consequences == | |
| + | 31 | For content arithmetic, trifluoroacetate joins water and residual solvent as a non-peptide fraction to be subtracted. A material at 99% chromatographic purity, 15% counterion and 6% water is roughly 78% peptide by mass, and the difference between the two figures is the difference between what a purity determination measures and what a purchaser is buying.{{r|usp1503}} The water term in that arithmetic must come from a water-specific determination rather than from a total volatiles figure.{{r|usp921}} | |
| + | 32 | ||
| + | 33 | For laboratory use, trifluoroacetate is not inert. It is reported to interfere with some cell-based assays at concentrations achievable when a peptide is dissolved directly, which is why acetate salts are sometimes specified for such work. That is a research consideration and nothing here is medical advice. | |
| + | 34 | ||
| 30 | == References == | 35 | == References == |
| 31 | {{reflist}} | 36 | {{reflist}} |
| ⋮ | ⋮ | ||
| 33 | <ref name="roux2008">Roux S, Zékri E, Rousseau B, et al. "Elimination and exchange of trifluoroacetate counter-ion from cationic peptides: a critical evaluation of different approaches." ''Journal of Peptide Science'' 14(3):354–359 (2008). PMID 17994590.</ref> | 38 | <ref name="roux2008">Roux S, Zékri E, Rousseau B, et al. "Elimination and exchange of trifluoroacetate counter-ion from cationic peptides: a critical evaluation of different approaches." ''Journal of Peptide Science'' 14(3):354–359 (2008). PMID 17994590.</ref> |
| 34 | <ref name="usp467">United States Pharmacopeia, General Chapter <467>, ''Residual Solvents''.</ref> | 39 | <ref name="usp467">United States Pharmacopeia, General Chapter <467>, ''Residual Solvents''.</ref> |
| + | 40 | <ref name="usp921">United States Pharmacopeia, General Chapter <921>, ''Water Determination''.</ref> | |
| 35 | 41 | ||
| 36 | == See also == | 42 | == See also == |