Medutest (revision 27)

Medutest is an independent testing service that analyses peptide samples submitted by purchasers and reports the results to the submitter. It is one of the four testing and review services referred to throughout this wiki, alongside Janoshik Analytical, PeptideMeter and VendorInvestigate.^[1]

Like any third-party analysis, a Medutest report is evidence about the material that reached the laboratory. Whether it can be extended to the lot from which that material came depends on how the sample was drawn, and whether it can be extended to a supplier depends on the number of lots examined and the period over which they were sampled.^[1]

Reports referenced on this wiki are those submitted by contributors. They are a self-selected sample and are not a survey of the market.

The determinations most often present in reports submitted to this wiki are chromatographic purity by area percent and, where commissioned, identity confirmation by mass. Some submissions include a peptide content figure; most do not.^[2]

The distinction matters more than it is usually given credit for. Purity is an area-normalised figure describing the composition of what was injected; content is a mass figure describing how much peptide is present. A material can be 99% pure and 60% peptide by mass, the balance being water, counterion and residual solvent — see Trifluoroacetate counterion and Loss on drying. Those two figures answer different questions and neither substitutes for the other.

Where a report and a supplier certificate both exist for a lot, comparison is only meaningful if the methods are comparable. Two purity figures obtained on different gradients are not directly comparable, and a difference of a few tenths of a percentage point is within ordinary method repeatability.^[2][3]

This wiki records what submitted documents state. It does not commission testing, does not hold samples, and does not verify that a submitted document is genuine beyond ordinary editorial scrutiny — a limitation described at Test report forgery.^[1]

Community submissions are aggregated in a tally that is explicitly labelled as self-reported. The tally counts submissions, not lots and not purchases, and a supplier with more submissions is not thereby better characterised in any statistical sense: it may simply have more customers who report.

Where a submission is used to support a statement in an article, the statement is attributed to the submission rather than presented as an established fact about the supplier. This is a requirement of the sourcing guidelines rather than a courtesy.

Results from different testing services are not automatically comparable. Two laboratories analysing splits of the same sample can return figures differing by several tenths of a percentage point through ordinary method differences, and larger differences arise when the methods differ in specificity rather than only in conditions.^[4]

The last row is the one that matters. A method that does not resolve a close-eluting impurity will report it as part of the main peak, and the resulting figure will be higher than that from a method that does resolve it — not because the material differs but because the question asked differs. See Analytical method validation.^[2]

• Third-party testing
• Janoshik Analytical
• PeptideMeter
• VendorInvestigate
• Peptide content
• Analytical method validation