Peptide content: difference between revisions
Diff·revision 14 → 15·21:04, 4 Apr 2025
Difference between revision 14 and revision 15 of Peptide content. 2 lines changed; the page grew by 351 bytes.
| Revision 14 — 08:51, 9 Mar 2025 GradientGus (talk) add the sample preparation, since the result depends on it 6,547 bytes +469 | Revision 15 — 21:04, 4 Apr 2025 LeanMassLars (talk) add the figure for the chromatogram and caption its axes 6,898 bytes +351 | ||
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| 44 | '''Determination by difference.''' Water, counterion and residual solvent are each measured and subtracted from unity. This is the route most certificates take when they report content at all, and it is sound provided every subtracted term was measured rather than assumed. Where the counterion figure is inferred from the synthesis route rather than determined by ion chromatography, the resulting content figure carries that assumption, and a certificate should say which was done.{{r|usp1503,iso17025}} | 44 | '''Determination by difference.''' Water, counterion and residual solvent are each measured and subtracted from unity. This is the route most certificates take when they report content at all, and it is sound provided every subtracted term was measured rather than assumed. Where the counterion figure is inferred from the synthesis route rather than determined by ion chromatography, the resulting content figure carries that assumption, and a certificate should say which was done.{{r|usp1503,iso17025}} |
| 45 | 45 | ||
| + | 46 | Neither route is affected by chromatographic purity, and purity cannot substitute for either. This is worth stating flatly because a certificate reporting only purity is sometimes described as reporting content, and the substitution is not a rounding matter — it is the difference between 99% and 83% in the worked case at [[Area percent purity]]. | |
| + | 47 | ||
| 46 | === Reconstitution arithmetic with content === | 48 | === Reconstitution arithmetic with content === |
| 47 | A vial is labelled 5 mg. Its certificate reports 99.1% [[Area percent purity|area percent]] and 82% peptide content. The purchaser adds 2 mL of [[Bacteriostatic water|bacteriostatic water]]. | 49 | A vial is labelled 5 mg. Its certificate reports 99.1% [[Area percent purity|area percent]] and 82% peptide content. The purchaser adds 2 mL of [[Bacteriostatic water|bacteriostatic water]]. |