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Onex Peptides, Canadian research peptide supplier

Quality

Testing Methodology

Two instruments answer two different questions, and a certificate that only reports one of them is only half an answer.

Identity: mass spectrometry

Mass spectrometry ionises the sample and measures the mass-to-charge ratio of what comes off. For a peptide, the result is compared against the theoretical molecular weight of the declared sequence. If the observed mass does not match the expected mass within tolerance, the vial does not contain the compound on the label — and that is not a purity problem, it is a different substance.

Identity is checked first and separately for that reason. A lot that is 99.6% pure something else passes a purity assay and fails the only test that matters.

Purity: reverse-phase HPLC

High-performance liquid chromatography pushes the dissolved sample through a column packed with a hydrophobic stationary phase. Components separate by how strongly they interact with that phase and come off at different times, and a detector — typically UV at 214 nm, where the peptide bond absorbs — records what passes.

The output is a chromatogram: a trace with a large peak for the target compound and smaller peaks for everything else. Purity is reported as the area of the target peak as a percentage of total peak area. Our release specification is >99% (HPLC), which means a lot is not sold unless the target peak accounts for more than 99% of the integrated area.

How to read a chromatogram

The number is the summary; the trace is the evidence. Four things are worth looking at on any chromatogram you are given:

  • Is there one dominant peak? A single tall, narrow peak with a flat baseline either side is what a clean lot looks like.
  • Is the main peak symmetrical?A peak that trails off to the right — “tailing” — can indicate a column problem or a co-eluting impurity sitting under the shoulder.
  • What are the small peaks? Trace peaks are normal. One large secondary peak at 0.8% is a different situation from eight peaks at 0.1%, even though both integrate to 99.2%.
  • Is the baseline flat? A drifting or noisy baseline makes the integration — and therefore the percentage — less reliable than it looks.

What a purity figure does not tell you

This is the part most buyers do not get told. A UV-area purity figure describes the proportion of UV-absorbing material, and several things a vial can contain do not absorb at 214 nm well or at all:

  • Water. A lyophilised cake retains residual moisture, and it is invisible to this assay. Peptide content by weight is almost always lower than the purity percentage suggests.
  • Counter-ions. Peptides are usually supplied as a salt — trifluoroacetate is common after purification — and the counter-ion is part of the mass in the vial.
  • Residual solvent and salts from synthesis and purification, which likewise do not show as peaks.

None of that makes the figure useless. It makes it one measurement of one property, and a supplier presenting it as a complete description of what is in the vial is overstating it. Peptide content by amino acid analysis is the assay that answers the weight question, and it is not routinely run on catalogue material anywhere in this category, including here.

What this site does not claim

No accreditation, no named third-party laboratory and no stated detection limit appear on this page or on any certificate link from it. Those are claims about arrangements that have to be verifiable before they are published. Everything above describes methods and what they measure, which is a thing that can be checked against any analytical chemistry reference.

See the certificate archive for how to match a certificate to the lot you received.