Karl Fischer Titration
Definition
The standard volumetric assay for water content in a dry solid, using an iodine reaction specific to water. On a lyophilised peptide it reports residual moisture, which is a stability predictor, and it shares only its name with dose titration.
In more detail
Karl Fischer titration measures water content specifically, through a reaction that consumes water, rather than inferring it from mass lost on drying. For a lyophilised peptide that specificity matters, because loss on drying also drives off residual solvent and counts it as water.
The result is what allows a purity figure to be converted between an as-received and an anhydrous basis. Without it the two cannot be related, and a certificate quoting an anhydrous figure with no water determination behind it has made an assumption rather than a measurement.
The name is also a useful reminder that vocabulary is context-dependent: titration here is a volumetric assay, and has nothing to do with the clinical sense of the same word.
Terms used in this definition
Other entries this definition refers to.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
Purity
The proportion of a sample that is the intended peptide rather than related impurities, measured chromatographically and quoted as a percentage. It says nothing about identity, sterility or endotoxin content, each of which is a separate test. Volta releases every batch against a >99% HPLC specification.
Endotoxin
Lipopolysaccharide from the outer membrane of Gram-negative bacteria. It survives ordinary sterilisation and is not removed by filtration alone, and it provokes a febrile inflammatory response, which is why it is assayed separately from sterility.
LAL Test (Limulus Amebocyte Lysate)
The endotoxin assay, which uses a clotting cascade from horseshoe crab blood that endotoxin triggers. A result on a certificate is a quantity against a limit, not a yes or no.
Sterility Testing
Incubation of a sample in growth media to confirm no viable microorganism is present. Sterility is a property of a validated process and its container and is independent of chemical purity: a very pure material can be non-sterile and often is.
Sterility
The absence of viable microorganisms in a preparation. It is conferred by a process and preserved by a closure, so it is lost the moment either is compromised and nothing about the appearance of a vial reports that.
Assay
Any procedure that measures whether something is present, how much of it there is, or how active it is. Analytical assays report composition; functional assays report activity, and a material can pass one and fail the other.
Quality Control (QC)
The testing a batch passes through before release, typically identity by mass spectrometry, purity by HPLC, content and, where relevant, water, sterility and endotoxin. QC is the set of tests; the certificate is the report of their results.
Degradation Product
A compound formed as a peptide breaks down, through oxidation, deamidation, hydrolysis or aggregation. Certificates report these as impurity peaks, and their pattern says more about how a batch was handled than the headline purity figure does.