Every certificate of analysis makes the same implicit promise: this number is the truth about what's in the vial. So we decided to test that promise directly. Over six weeks, we split four commercial peptide batches — sourced through ordinary retail channels, the way any buyer would get them — and sent identical portions of each to three accredited third-party labs, without telling any of them the others were involved.
The results were not identical. On one BPC-157 batch, purity readings ranged from 97.6% to 99.3% — a gap that, on paper, looks like it separates a mediocre batch from an excellent one. On a GHK-Cu sample, two labs agreed within a tenth of a percentage point, while a third came in nearly two points lower and flagged a minor secondary peak the other two didn't report at all.
Same Vial, Different Machines
The explanation isn't fraud, and it isn't incompetence. It's method. HPLC purity testing — the industry standard — requires choices at almost every step: which wavelength to monitor, how to define the baseline, which reference standard to calibrate against, and where exactly a peak's boundaries are drawn when it isn't perfectly clean. Two well-run labs, both doing everything correctly, can land in different places because they made different reasonable choices.
“A purity percentage without a method behind it is a rumor, not a result,” says Dr. Priya Anand, an analytical chemist who reviewed our raw chromatography data for this piece. “The number by itself tells you almost nothing. The method section — which most consumer-facing COAs don't even include — is where the actual information lives.”
“The number by itself tells you almost nothing. The method section is where the actual information lives.”
— Dr. Priya Anand, analytical chemistWhat This Doesn't Mean
It would be easy to read this investigation as an argument that third-party testing is theater. That's not what we found. Every lab we used caught real problems in at least one sample across our testing — an unlabeled secondary compound here, a quantity that didn't match the stated fill there. The variance we found was almost entirely in the second decimal place of legitimate, competently-run analysis, not in whether a batch was fundamentally what it claimed to be.
The takeaway isn't to distrust COAs. It's to read them the way you'd read any scientific claim — with attention to method, not just headline number. A batch tested by a lab that publishes its reference standards, discloses its instrument and column type, and reports quantity alongside purity is giving you more real information than one that hands you a single clean percentage and nothing else.
What We're Asking Suppliers to Change
- Publish the testing method (HPLC-UV, LC-MS, etc.) alongside every purity figure, not just the number.
- Report quantity as well as purity — a high percentage of a low fill tells a very different story than a high percentage of an accurate one.
- Disclose when sterility or endotoxin results are still pending, rather than omitting the row entirely.
None of this requires new regulation or new technology. It requires suppliers to publish what their labs already generate. The information gap here isn't in the testing — it's in what makes it to the buyer.