Medutest (revision 4)

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]

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]