COA education

The baseline. Every other test on the COA is only meaningful if the molecule was identified correctly first. Without identification testing, there is no objective check that the vial matches the label.

Most commonly LC-MS (liquid chromatography combined with mass spectrometry). The sample is ionized and fragmented; the instrument records mass-to-charge ratios. The pattern is compared to the expected pattern for the labeled compound. A match supports correct identity. A mismatch points to mislabeling, substitution, or a synthesis error.

Look for an Identification line with 'Conforms' or 'Pass' and a specified method (LC-MS, MS, or similar). Bonus signal: the COA shows the actual mass match, not just a pass/fail.

Vial labels often state total mass, but peptides are typically supplied as salts (TFA, acetate, etc) — and the counterion has weight. Net content tells you how much active peptide is present versus how much is salt + filler. Affects how your dose math actually works.

HPLC (high-performance liquid chromatography) with quantitative comparison to a certified reference standard of known concentration. The sample is separated on a column; the target peptide produces a peak; peak response is compared to the reference to estimate the actual amount.

Look for 'Net Content', 'Assay', or 'Peptide Content' as a percentage of label claim. Industry-acceptable bands are commonly cited around 95-105% of claim. Far outside that range deserves scrutiny.

Identification confirms which compound is present. Purity tells you what fraction of the material is the target peptide versus impurities — truncated sequences from incomplete coupling, deletion sequences, oxidized residues, aggregates, residual reagents. Some impurities are biologically active. Some are inert. None of them are what you paid for.

HPLC chromatogram with peak integration. Purity is calculated as the main peak area divided by the sum of all peak areas. UV detection at 214 nm is common because it picks up peptide bonds across all residues.

'Purity' or 'Net Purity' as a percent with method specified (RP-HPLC most commonly). For research peptides, 98%+ is a widely cited expectation. Below 98% on a research-grade label is a red flag worth investigating.

Endotoxins are toxic outer-wall components of Gram-negative bacteria — most commonly lipopolysaccharide (LPS). They are released when bacterial cells break apart and persist after the organisms themselves are killed or filtered. Sterile filtration (0.22 micrometer) removes intact bacteria but does not remove endotoxin molecules, which are far smaller. A 'sterile' product can carry meaningful endotoxin load. The immune system reacts strongly to LPS.

LAL (Limulus Amebocyte Lysate) is the long-standing standard, sensitive to LPS, reported in endotoxin units per mg or per mL. Some labs use rFC (recombinant Factor C) as an alternative that targets the same biology with a different reagent source.

An 'Endotoxins' or 'Bacterial Endotoxins' line with a numeric result and an acceptance limit. Method (LAL or rFC) should be specified. If a vendor says 'sterile' but never tests endotoxins, you have an information gap.

Sterility testing checks for viable bacteria (aerobic and anaerobic), yeasts, and molds in a portion of the lot. Distinct from endotoxin testing — sterility addresses living organisms; endotoxin addresses their leftover toxic components.

Direct inoculation: sample (or extract) is added to growth media and incubated under aerobic and anaerobic conditions. Membrane filtration: sample is filtered, the filter is transferred to media. Typical incubation periods run 14 days for classical methods (USP <71> or equivalent).

'Sterility' with 'Pass' or 'No growth' and a cited method (USP <71> is the common reference). Note: sterility tests a sample, not the entire batch — one passing COA does not guarantee every unit. Most informative alongside endotoxin data and disclosed manufacturing controls.

Elemental contaminants — lead, arsenic, cadmium, mercury, and sometimes catalyst residues like palladium — can enter peptide manufacturing through reagents, solvents, equipment leaching, or amino-acid raw materials with poor trace-metal backgrounds. A peptide can pass every microbial test and still fail elemental limits.

ICP-MS (inductively coupled plasma mass spectrometry) is the standard. The matrix is atomized in a plasma; masses are separated and quantified at parts-per-billion levels. ICP-OES (optical emission) is an alternative.

'Heavy metals' or 'Elemental impurities' with per-element results in ppm or ppb. Limits are commonly referenced against frameworks like USP <232> and ICH Q3D in regulated contexts. The COA should state which limits apply.

All the tests above are typically run on one representative sample from a lot. That proves that one sample passed at that time. It does not catch uneven filling, partial contamination, or vial-to-vial variation. Conformity testing pulls multiple vials from the same lot and re-runs identification, content, and purity to check consistency.

Multiple sample pulls from the same lot, each tested for identification, net content, and net purity. Results are reported alongside or in addition to the primary COA.

Multiple data points for the same lot — either an extended report with several sample IDs or a separate conformity summary. Vendors that disclose conformity testing are signaling investment in batch-level QC, not just spot-check QC.