A Certificate of Analysis (COA) looks intimidating the first time you open one. In practice, four sections do almost all the work.
1. HPLC purity (%)
Reverse-phase HPLC separates the target peptide from related impurities — truncated sequences, deletion peptides, oxidation products. The headline number is area percent at the detection wavelength (usually 220 nm).
Research-grade release spec: ≥ 99.0%. Anything below 95% should be treated as technical-grade material.
2. Mass spectrometry
ESI-MS confirms the molecular weight matches the theoretical mass of the intended sequence. A match within ±1 Da rules out the most common synthesis failures.
3. Counterion content
Solid-phase peptides ship as TFA or acetate salts. The COA reports the net peptide content after subtracting counterion and residual water — typically 75–90%. If you're dosing by mass, this is the number you weigh against.
4. Appearance & solubility
White lyophilized powder, soluble in the listed solvent. Off-color or partially insoluble material is a red flag — request a fresh lot.
If a vendor won't share the COA for the specific lot you received, treat that as the answer. Every Nuvex lot ships with its COA on request.