Peptide Testing FAQ

Purity is measured by reversed-phase HPLC (RP-HPLC), typically at 214 nm. The area percent of the main peak versus all detected peaks gives the purity value. A pharmaceutical-grade peptide is generally 98% or higher.

It means 99% of the material detected by HPLC at the assay wavelength is the target peptide, and 1% is related impurities (truncated sequences, deletion sequences, oxidations). It does not account for water, salt, or counterions, which are quantified separately.

Identity is confirmed by mass spectrometry (LC-MS or MALDI-TOF). The observed monoisotopic mass must match the theoretical mass of the target sequence within a few ppm.

HPLC separates and quantifies (how much of each species is present). Mass spec identifies (what each species actually is). A complete COA uses both.

Bacterial endotoxin (LAL), microbial bioburden, residual solvents (TFA, acetonitrile, DMF), heavy metals (USP <232>), and where relevant, sterility. Injectable peptides require endotoxin testing at a minimum.

Endotoxin (lipopolysaccharide, LPS) is a fever-inducing molecule from Gram-negative bacterial cell walls. Even at low concentrations it causes pyrogenic reactions in humans. USP limits it to strict thresholds for injectable products.

No. A 0.22 micron filter removes bacteria but endotoxin is a soluble molecule that passes through. Endotoxin removal requires affinity resins, ultrafiltration, or validated depyrogenation.

Water accelerates peptide hydrolysis, deamidation, and aggregation. Lyophilized peptides should be under about 5% residual water for good shelf life. Karl Fischer titration is the reference method.

Lyophilized (freeze-dried) peptides are shelf-stable powders with low water content. Non-lyophilized peptides are in solution or wet cake, which degrade faster and require cold-chain shipping.

Refrigerated 2 to 8°C for 7 to 28 days depending on the sequence, or aliquoted and frozen at -80°C for longer. Avoid freeze-thaw cycles. See our full storage protocol.

Stability testing places samples at defined temperature and humidity conditions (ICH Q1A) and re-tests at intervals. This establishes shelf life and storage claims.

Cost depends on the test panel. A basic HPLC purity + mass spec identity typically runs a few hundred dollars per sample. Adding endotoxin, moisture, and residual solvents increases scope.

Eligible routine testing takes 5 to 7 business days from sample receipt. Turnaround starts once the sample is logged in and payment is confirmed.

Request a quote with the peptide name, sequence if available, and the tests you need. We send a shipping label and instructions, and results are delivered as a signed PDF COA.

For any customer-facing claim, third-party testing is required to remove conflict of interest. In-house testing is only appropriate for internal process control.

ACS Laboratory is accredited by A2LA to ISO/IEC 17025:2017 within its certificate scope. Peptide HPLC and LC-MS scope coverage has not been confirmed. DEA registration is #RA0571996.

Roger Brown, President and co-founder, leads the laboratory. He has more than 35 years of experience in analytical testing and compliance.

The glossary defines terms like TFA, LAL, deamidation, retention time, and dozens more.