Every lot Chrome Labs releases is analysed before it reaches a bench. This guide explains what those analyses measure, how to read the numbers on a Certificate of Analysis (COA), and why batch traceability matters more than a headline purity percentage.
What HPLC actually measures
High-Performance Liquid Chromatography separates a sample into its component species by pushing it through a packed column under pressure. Each species elutes at a characteristic retention time and registers as a peak on the chromatogram. Purity is reported as the area of the target peak divided by the total area of all peaks — so "99.1% by HPLC" means the target compound accounts for 99.1% of the UV-absorbing material detected, not that the vial is 99.1% peptide by mass.
Reversed-phase HPLC (RP-HPLC) with a C18 column and a water/acetonitrile gradient containing 0.1% trifluoroacetic acid is the standard method for peptides. A clean chromatogram shows one dominant, symmetrical peak with a flat baseline; shoulders, tailing, or a cluster of early-eluting peaks usually indicate truncated sequences, deletion products, or residual synthesis reagents.
Why mass spectrometry is run alongside it
HPLC tells you how much of one thing there is; it does not confirm the thing is what the label says. Mass spectrometry (typically ESI-MS or MALDI-TOF for peptides) measures the molecular weight of the eluted species and confirms identity against the theoretical mass of the sequence. A lot that passes HPLC but fails MS identity is the classic failure mode behind mislabelled material.
Read the two together: HPLC for purity, MS for identity. A COA presenting only one of them is incomplete.
Reading a Certificate of Analysis
A usable COA is specific to a single production lot and states, at minimum: the compound name and sequence, the lot or batch number, the test date, the analytical method and instrument conditions, the measured purity with its chromatogram, the observed versus theoretical mass, and the name of the testing laboratory. Generic "typical results" documents with no lot number are marketing material, not analytical data.
Peptide content (net peptide by weight, often determined by nitrogen analysis or amino-acid analysis) is a separate figure from chromatographic purity. Lyophilised peptides carry counter-ions and residual water, so net peptide content is commonly 70–85% even when HPLC purity exceeds 98%. Both numbers matter when calculating working concentrations.
Batch traceability
Analytical data is only meaningful if it belongs to the vial in your hand. Chrome Labs links every COA to the specific lot it was drawn from, so the document you receive corresponds to the material shipped rather than to an earlier, unrelated production run. That linkage is what makes results reproducible across repeat orders and what lets you retire a suspect lot without discarding an entire inventory.
Third-party testing
In-house QC is a first pass, not independent verification. Third-party analysis by an unaffiliated laboratory removes the commercial incentive from the result. When evaluating any supplier, check whether the testing laboratory is named on the COA and whether it is separate from the seller.
Practical handling notes
Purity degrades with poor handling regardless of how the lot was released. Lyophilised peptides are generally stored at −20 °C or colder, protected from light and moisture; reconstituted solutions are far less stable and are typically held at 2–8 °C for short-term use. Repeated freeze–thaw cycles and exposure to ambient humidity are the two most common causes of a compound that no longer matches its release data.
Compliance
All Chrome Labs products are supplied strictly for in-vitro laboratory research by qualified professionals. They are not drugs, supplements, or medical devices, and are not for human or animal consumption. See the research use disclaimer for the full terms, or browse the catalog to see per-lot documentation.