Peptide content: difference between revisions

Diff·revision 12 → 13·19:27, 21 Feb 2025

Difference between revision 12 and revision 13 of Peptide content. 9 lines changed; the page grew by 1,146 bytes.

Revision 12 — 08:36, 30 Jan 2025 ImportRecordIna (talk) expand §Why it is so often absent 4,932 bytes +122	Revision 13 — 19:27, 21 Feb 2025 DiluentDiya (talk) add the equilibration time to the gradient description 6,078 bytes +1,146
42	'''Direct determination.''' Amino acid analysis hydrolyses the peptide and quantifies the released residues against a calibrated standard, giving the peptide mass directly. It is the reference approach and it is slow and comparatively expensive. Quantitative nitrogen determination is a faster direct route and is less specific, because any nitrogen-containing impurity contributes.	42	'''Direct determination.''' Amino acid analysis hydrolyses the peptide and quantifies the released residues against a calibrated standard, giving the peptide mass directly. It is the reference approach and it is slow and comparatively expensive. Quantitative nitrogen determination is a faster direct route and is less specific, because any nitrogen-containing impurity contributes.
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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}}
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+		46	=== 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]].
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+		49	The peptide mass present is 5 mg × 0.82 = 4.1 mg. The concentration is therefore 4.1 mg ÷ 2 mL = 2.05 mg/mL, not the 2.5 mg/mL that the nominal label alone would give — a difference of 18%.
+		50
44	== References ==	51	== References ==
45	{{reflist}}	52	{{reflist}}
46	<ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, "Quality Attributes of Synthetic Peptide Drug Substances" (informational). USP–NF, current revision. Sets out peptide content as an attribute distinct from chromatographic purity.</ref>	53	<ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, "Quality Attributes of Synthetic Peptide Drug Substances" (informational). USP–NF, current revision. Sets out peptide content as an attribute distinct from chromatographic purity.</ref>
+		54	<ref name="iso17025">ISO/IEC 17025:2017, ''General requirements for the competence of testing and calibration laboratories''. International Organization for Standardization.</ref>
47	<ref name="ichq3c">International Council for Harmonisation, ''Q3C: Impurities — Guideline for Residual Solvents''. Classifies solvents by toxicity and sets concentration limits; the acetonitrile used in preparative purification falls in the second class.</ref>	55	<ref name="ichq3c">International Council for Harmonisation, ''Q3C: Impurities — Guideline for Residual Solvents''. Classifies solvents by toxicity and sets concentration limits; the acetonitrile used in preparative purification falls in the second class.</ref>
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52	* [[Certificate of analysis]]	60	* [[Certificate of analysis]]
53	* [[Lyophilisation]]	61	* [[Lyophilisation]]
+		62	* [[Reference standard]]
54		63
55	{{DEFAULTSORT:Peptide content}}	64	{{DEFAULTSORT:Peptide content}}