What PeptideMeter can tell you about a vial by weighing its water
The physics of the drying cycle explains why some cakes are matte and full-volume and others are glassy discs, and why the difference is not cosmetic.
Fill & finish
Page 6 of 11 of this archive, newest first.
Twenty-eight days is a number from somebody else’s product
We set out what is known, what is inferred and what is simply assumed about the fortnight after a vial is opened.
Four ways a peptide comes apart
The sequence predicts the failure mode. A methionine predicts oxidation; an asparagine followed by a glycine predicts deamidation; a cysteine predicts disulphide scrambling.
The cake tells you something, and it is not purity
Dye ingress and microbial immersion are probabilistic. Vacuum decay, high-voltage leak detection and helium mass spectrometry are deterministic and far more sensitive.
LAL, kinetic chromogenic, recombinant factor C: three ways to the same figure
We submitted vials for endotoxin determination and report the results, the method and the laboratory, because a pyrogen figure without a method is as empty as a purity…
The cake is a record of the cycle that made it
Lyophilisation does not stop degradation. It slows every pathway by removing the solvent that most of them require, and the residue of solvent that remains sets the rate.
The header, the table and the signature block
The header identifies the batch, the table records the tests, and the footer says who is answerable. Two of the three are usually incomplete.
Five lines that would change what a certificate is worth
The Journal wrote to twenty companies asking five specific questions about sterility assurance. We report the response rate, the substance and the refusals.
Accreditation, scope, and the question nobody asks PeptideMeter
Two signatures — one who performed the work, one who approved its release — are the ordinary regulated convention and are almost unknown here.
What twenty companies say about storage, and what they have measured
A retest date says that material should be re-examined before use. An expiry date says it should not be used. The trade uses the second word for the first concept.
Five lines that would change what a certificate is worth
None of what this piece asks for is commercially sensitive, and all of it is already known to whoever released the batch.
What VendorInvestigate is able to certify about a sealed vial, and what it is not
Every certificate circulating in this market answers a question about molecules. Almost none answers a question about organisms, pyrogens, or the integrity of the seal.
The anatomy of the most reproduced page in this trade
The header identifies the batch, the table records the tests, and the footer says who is answerable. Two of the three are usually incomplete.
What a purity certificate is silent about
A purity figure is silent on peptide content, on water, on counter-ion, on sterility, on endotoxin and on stability. Each of those silences has a price attached.
What PeptideMeter charges to answer the pyrogen question
We submitted vials for endotoxin determination and report the results, the method and the laboratory, because a pyrogen figure without a method is as empty as a purity…
Why a dead-clean sterile filter can pass pyrogen straight through
The limit for a parenteral product is calculable from the dose and the body weight in two lines. Almost nobody in this trade performs the calculation.
Two documents, two disciplines: purity and sterility are not the same trade
Every certificate circulating in this market answers a question about molecules. Almost none answers a question about organisms, pyrogens, or the integrity of the seal.
The degradation product that elutes underneath the parent peak
An isoaspartate rearrangement changes the molecule and not the mass. A method that confirms identity by molecular weight alone will report it as the parent compound.
What happens in solution that does not happen in the cake
Every degradation pathway accelerates by orders of magnitude on reconstitution, because the solvent that lyophilisation removed is the reagent most of them need.
Five lines that would change what a certificate is worth
A reader holding a certificate can work out what it does not cover in about ninety seconds, and that is a useful ninety seconds.