Why a blend report has no purity percentage — and what to read instead

Look at the independent report for Glow on our testing page and you will see three numbers: GHK-Cu 21.84 mg/ml, TB-500 3.38 mg/ml, BPC-157 3.86 mg/ml. You will not see a purity percentage. Next to a single-peptide report, where 98.86% or 99.59% sits in bold, that can look like something is missing. It is not. It is what a correct report for a mixture looks like, and the laboratory that issued it will not write a purity figure for a blend at all. Here is why, and what the three numbers tell you instead.

What purity measures, and why it needs one peak

Purity by HPLC is a ratio. The instrument separates the sample into its components, each one leaves the column at a different time and is recorded as a peak, and purity is the area of the main peak divided by the total area of all peaks. Everything that is not the main peak is, by definition, an impurity.

That definition works because a single-peptide product has one intended component. A blend has two or three. Run Glow through the column and you get a peak for GHK-Cu, a peak for TB-500, a peak for BPC-157, and small peaks for the impurities of each. Which is the "main" peak? None of them. Divide any one by the total and you get the fraction of the mixture that peptide makes up, not its purity. Divide the three together by the total and you get a number that hides whether any one of them is degraded. The ratio does not answer a question anyone is asking.

There is a further, practical problem. Three peptides in one solution can partially co-elute — leave the column at overlapping times — and where peaks overlap, the software cannot cleanly assign area to one or the other. Peak-purity assessment for co-eluting components is a known limitation of area-percent methods, addressed in the chromatography literature with additional detection techniques rather than a headline percentage. A lab that reports a single figure for a blend anyway is reporting something it cannot stand behind.

What the lab actually does with a blend

Janoshik's published price list is explicit: for blend products such as Glow-type mixtures, the analysis reports identity and amount of each component, and states that peptide purity is not included. That is not a gap in the service. It is the lab declining to invent a number.

So a blend report gives you, per peptide:

• Identity — mass spectrometry confirms each named peptide is present at its expected molecular mass.
• Quantity — the measured concentration of each, in mg/ml, against a reference standard.

For a buyer that is the more useful document. It answers "is everything the label names actually in here?" and "in the amounts claimed?", which are the two questions underdosing and substitution turn on. A single purity percentage, even if it could be calculated, would answer neither.

Reading the Glow report

Glow is labelled as 70 mg across two pens: GHK-Cu 50 mg, TB-500 10 mg, BPC-157 10 mg. The independent report on batch GL70-3.0-20260429 gives GHK-Cu at 21.84 mg/ml, TB-500 at 3.38 mg/ml and BPC-157 at 3.86 mg/ml. Read it as a recipe check:

1. Are all three present? Yes — each is identified by mass.
2. Are the proportions right? GHK-Cu should be about five times each of the other two. 21.84 against 3.38 and 3.86 is that ratio, within the method's tolerance.
3. Does the concentration times fill volume give the labelled content? That is the arithmetic the quantity article walks through for single peptides, and it applies the same way here, per component.

What you cannot read from it is the purity of each peptide within the blend, and that is the honest limit. The place that purity is established is upstream: each raw peptide is tested as a single compound before it is combined, and that is where a purity figure belongs. It is a separate document from a blend report, and a fair thing to ask a vendor for.

What a "99% pure blend" claim means

You will see it on other sites: a BPC-157 and TB-500 blend, "99% pure". One of two things is true. Either the vendor is quoting the purity of the individual raw materials before mixing, in which case the number is real but describes a stage of manufacture, not the product; or the vendor has written a purity figure because buyers expect one. Neither is a measurement of the blend. A vendor who can explain which it is has been careful; a vendor who cannot has been careless with the one thing they are asking you to trust.

How Biovanta reports blends

For Glow and for BPC-157 + TB-500, the independent report is published as the lab issues it: identity and measured content per peptide, batch, task number and verification key, with no purity percentage added by us. Purity, where it is measured, is measured on each raw peptide as a single compound before blending — a different document with a different job. Neither pretends to be the other. Products are supplied strictly for in-vitro laboratory research.