Loss on drying: difference between revisions
Diff·revision 4 → 5·08:51, 21 Sep 2024
Difference between revision 4 and revision 5 of Loss on drying. 3 lines changed; the page grew by 472 bytes.
| Revision 4 — 08:20, 7 Sep 2024 SigFigSindri (talk) British spelling per PP:MOS 1,765 bytes +534 | Revision 5 — 08:51, 21 Sep 2024 LOD_Lorcan (talk) consistent en dashes in ranges 2,237 bytes +472 | ||
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| 11 | It is not a water determination. The mass lost comprises water and any other volatile component — residual acetonitrile, acetic acid, ammonia from a salt-exchange step — so a loss-on-drying figure is an upper bound on water content rather than a measurement of it. [[Karl Fischer titration|Karl Fischer titration]] measures water specifically and will generally give a lower number on the same material.{{r|usp921}} | 11 | It is not a water determination. The mass lost comprises water and any other volatile component — residual acetonitrile, acetic acid, ammonia from a salt-exchange step — so a loss-on-drying figure is an upper bound on water content rather than a measurement of it. [[Karl Fischer titration|Karl Fischer titration]] measures water specifically and will generally give a lower number on the same material.{{r|usp921}} |
| 12 | 12 | ||
| + | 13 | For peptides the two are frequently confused, and a certificate reporting "water: 6.2% (LOD)" is reporting something other than water. The distinction matters because water is subtracted in calculating [[Peptide content|peptide content]], and using a loss-on-drying figure for that subtraction understates the peptide.{{r|usp1503}} | |
| + | 14 | ||
| 13 | == Method == | 15 | == Method == |
| 14 | A weighed sample is dried to constant mass under stated conditions — an oven at a specified temperature, or a desiccator over a specified desiccant, or under vacuum — and the mass difference expressed as a percentage of the starting mass.{{r|usp731}} | 16 | A weighed sample is dried to constant mass under stated conditions — an oven at a specified temperature, or a desiccator over a specified desiccant, or under vacuum — and the mass difference expressed as a percentage of the starting mass.{{r|usp731}} |
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| 20 | <ref name="usp731">United States Pharmacopeia, General Chapter <731>, ''Loss on Drying''.</ref> | 22 | <ref name="usp731">United States Pharmacopeia, General Chapter <731>, ''Loss on Drying''.</ref> |
| 21 | <ref name="usp921">United States Pharmacopeia, General Chapter <921>, ''Water Determination''.</ref> | 23 | <ref name="usp921">United States Pharmacopeia, General Chapter <921>, ''Water Determination''.</ref> |
| + | 24 | <ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, ''Quality Attributes of Synthetic Peptide Drug Substances''.</ref> | |
| 22 | 25 | ||
| 23 | {{DEFAULTSORT:Loss on drying}} | 26 | {{DEFAULTSORT:Loss on drying}} |