Purity claim inflation: difference between revisions
Diff·revision 11 → 12·20:03, 6 Feb 2025
Difference between revision 11 and revision 12 of Purity claim inflation. 6 lines changed; the page grew by 536 bytes.
| Revision 11 — 15:22, 26 Jan 2025 ExenatideEzra (talk) add the second-opinion point: two services, one lot, is a stronger record 3,067 bytes ±0 | Revision 12 — 20:03, 6 Feb 2025 LOD_Lorcan (talk) add the laboratory accreditation status, or say plainly that it is not stated 3,603 bytes +536 | ||
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| 1 | {{Infobox concept | 1 | {{Infobox concept |
| 2 | | name = Purity claim inflation | 2 | | name = Purity claim inflation |
| + | 3 | | subtitle = Quality failure | |
| 3 | | image = purity-hist.svg | 4 | | image = purity-hist.svg |
| 4 | | caption = The same material can be described by several defensible numbers, and the largest is usually chosen. | 5 | | caption = The same material can be described by several defensible numbers, and the largest is usually chosen. |
| ⋮ | ⋮ | ||
| 26 | 27 | ||
| 27 | The detection-wavelength point is the least appreciated. Peptide purity is usually determined at 214 nm, where the amide bond absorbs, so response is roughly proportional to the number of bonds and impurities are detected reasonably. A determination at 280 nm, where aromatic side chains absorb, will systematically under-detect impurities lacking those residues. Both are legitimate methods; they do not answer the same question. | 28 | The detection-wavelength point is the least appreciated. Peptide purity is usually determined at 214 nm, where the amide bond absorbs, so response is roughly proportional to the number of bonds and impurities are detected reasonably. A determination at 280 nm, where aromatic side chains absorb, will systematically under-detect impurities lacking those residues. Both are legitimate methods; they do not answer the same question. |
| + | 29 | ||
| + | 30 | == What a purity figure does establish == | |
| + | 31 | An area percent purity figure establishes that, of the material detected by that detector under those conditions, the stated proportion eluted as the main peak. That is a real and useful fact and this article should not be read as dismissing it.{{r|usp1503}} | |
| + | 32 | ||
| + | 33 | What it does not establish: how much peptide is in the vial; that the main peak is the intended molecule; that undetected species are absent; that the figure would be reproduced on a different method. | |
| 28 | 34 | ||
| 29 | == References == | 35 | == References == |