Lab handling library

Guides to handling research peptides in the lab: storage, solution preparation by concentration, and reading certificates of analysis.

• How to read a peptide certificate of analysisRead a peptide certificate of analysis field by field: confirm the lot matches your vial, find which laboratory ran the analysis, check whether purity is a measured HPLC area percentage or a floor, and see whether identity was confirmed by mass spectrometry. Then check what else was tested, against what limits, and whether the laboratory can verify the document.
• HPLC vs mass spec: what each test provesHPLC with UV detection measures chromatographic purity: the main peak's share of the detected peak area. Mass spectrometry measures molecular mass, which confirms identity. Each answers a different question. HPLC cannot say what the main peak is, and MS cannot say how much of the sample it is. Neither measures peptide content, counter-ions, water or endotoxin.
• Peptide purity: 98% vs 99% in practiceA peptide's purity figure is the main peak's share of HPLC peak area at one wavelength, for one lot. The remaining 1–2% is usually related peptides: deletion or truncated sequences, oxidized, deamidated or racemized forms. Whether one point matters depends on the experiment, and purity says nothing about net peptide content.