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Guides to peptide testing, COAs and lab methods from Lotmark Labs

PEPTIDE TESTING · COAs · LAB METHODS

Diagram of a peptide certificate of analysis with the lot number, HPLC purity, identity and endotoxin sections labeled

How to Read a Peptide Certificate of Analysis (COA)

A line-by-line guide to a peptide COA: lot number, HPLC purity, identity, quantity, endotoxin and heavy metals, plus the checks that make a report trustworthy.

Oct 14, 2026 · 7 min read

HPLC chromatogram with one tall main peptide peak and small impurity peaks, labeled with retention time and area percent

HPLC Purity Testing Explained: What the Percentage Really Means

How reversed-phase HPLC measures peptide purity, what the area % does and doesn't tell you, and how to read a chromatogram on a COA.

Oct 14, 2026 · 7 min read

Stacked bar showing the weight of a peptide vial split into peptide, counterions and water, next to a 99 percent purity figure

Purity vs. Net Peptide Content: Why a 99% Pure Vial Can Hold Less Peptide

HPLC purity and net peptide content measure different things. Learn how counterions, water and salts change how much peptide is really in a vial, with a worked example.

Oct 14, 2026 · 6 min read

Two panels: matching HPLC peaks for a sample and a reference standard, and a mass spectrum with the observed mass matching the expected mass

Peptide Identity Testing: HPLC Retention Time vs. LC-MS

Purity doesn't prove a vial holds the right compound. How identity is confirmed by HPLC retention time matching and by LC-MS mass, and the limits of each.

Oct 14, 2026 · 6 min read

Kinetic chromogenic LAL standard curve plotting onset time against endotoxin concentration, with a sample result marked in EU/mg

Endotoxin Testing (USP <85>): What EU/mg Results Mean

What bacterial endotoxins are, how the LAL test works under USP <85> (gel-clot, turbidimetric, chromogenic), what EU/mg means, and how limits are set.

Oct 14, 2026 · 7 min read

Element tiles for lead, cadmium, arsenic and mercury with ICP-MS results in parts per billion

Heavy Metals Testing: ICP-MS, USP <232>/<233> and ICH Q3D

How elemental impurities are tested by ICP-MS, what USP <232>, <233> and ICH Q3D cover, the Class 1 elements, and how to read a heavy metals result on a COA.

Oct 14, 2026 · 6 min read

Timeline comparing a 14-day USP 71 sterility incubation with a rapid microbial method that returns results in days

Sterility Testing: USP <71> vs. Rapid Microbial Methods

How the compendial USP <71> sterility test works, why it takes at least 14 days, how rapid methods are validated under USP <1223>, and what a sterility result can and can't prove.

Oct 14, 2026 · 6 min read

An accreditation certificate beside a scope table listing test methods, with a check mark next to HPLC purity

What ISO/IEC 17025 Accreditation Means (and How to Check a Lab's Scope)

What ISO/IEC 17025 accreditation covers, how it differs from ISO 9001 certification, and how to check a lab's certificate and scope with its accreditation body.

Oct 14, 2026 · 6 min read

A certificate of analysis with red markers on a mismatched lot number, a missing lab name and an edited purity figure

How to Spot a Fake or Altered COA: 9 Red Flags

Nine signs a certificate of analysis has been faked, edited or reused, and how to verify a COA directly with the lab that issued it.

Oct 14, 2026 · 6 min read

Flow from production lot to an independent lab to a verified certificate, compared with a supplier issuing its own certificate

Third-Party Testing vs. Supplier COAs: Why Every Lot Matters

Why independent, lot-specific testing is stronger evidence than a supplier's own COA, what chain of custody means, and how to submit samples for third-party testing.

Oct 14, 2026 · 7 min read