Trifluoroacetate counterion: difference between revisions
Diff·revision 11 → 12·01:08, 18 Jan 2025
Difference between revision 11 and revision 12 of Trifluoroacetate counterion. 6 lines changed; the page grew by 617 bytes.
| Revision 11 — 19:52, 1 Jan 2025 Areapercent_Ayo (talk) rm the assertion that two laboratories must agree; they need not 2,739 bytes ±0 | Revision 12 — 01:08, 18 Jan 2025 AnalyticalAnnie (talk) rm the claim that the method is stability-indicating without a forced-degradation study 3,356 bytes +617 | ||
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| 1 | {{Infobox concept | 1 | {{Infobox concept |
| 2 | | name = Trifluoroacetate counterion | 2 | | name = Trifluoroacetate counterion |
| + | 3 | | subtitle = Impurity and salt form | |
| 3 | | Abbreviation = TFA salt | 4 | | Abbreviation = TFA salt |
| 4 | | Arises from = Trifluoroacetic acid modifier in [[Reverse-phase HPLC|RP-HPLC]] | 5 | | Arises from = Trifluoroacetic acid modifier in [[Reverse-phase HPLC|RP-HPLC]] |
| ⋮ | ⋮ | ||
| 19 | 20 | ||
| 20 | Complete removal is difficult, and residual trifluoroacetate persists at low levels even after exchange. A certificate reporting an acetate salt should therefore also report residual trifluoroacetate if the exchange is to be evidenced rather than asserted.{{r|roux2008}} | 21 | Complete removal is difficult, and residual trifluoroacetate persists at low levels even after exchange. A certificate reporting an acetate salt should therefore also report residual trifluoroacetate if the exchange is to be evidenced rather than asserted.{{r|roux2008}} |
| + | 22 | ||
| + | 23 | == Determination == | |
| + | 24 | Trifluoroacetate content is determined by ion chromatography with conductivity detection, by capillary electrophoresis, or by fluorine nuclear magnetic resonance. Each gives a mass fraction of trifluoroacetate in the solid.{{r|usp1503}} | |
| + | 25 | ||
| + | 26 | It is not detected by ordinary [[Reverse-phase HPLC|reverse-phase]] purity determination — it does not absorb usefully at 214 nm and elutes near the void — so a purity figure is entirely unaffected by how much of it is present. This is the clearest single example of why purity and content are not interchangeable. | |
| 21 | 27 | ||
| 22 | == References == | 28 | == References == |