Working Stock
Definition
A diluted solution prepared from a concentrated one for day-to-day use, so the concentrated stock is disturbed as rarely as possible. The dilution factor and the date belong on the label, because a working stock is the thing most likely to be misidentified later.
What this means for research sourcing
Getting this right matters when preparing lyophilized research peptides for in vitro work. Volta ships compounds as lyophilized powder for reconstitution.
Related Terms in Preparation
Excipient
Anything in a formulation other than the active substance: bulking agents, buffers, preservatives, stabilisers. Excipients decide how a cake looks and how well it redissolves, and they appear on an approved label alongside the active.
Mannitol
A sugar alcohol used as a bulking agent and cryoprotectant in freeze-dried formulations. It gives the cake its visible structure and shields the peptide during drying, so a vial that looks empty often simply has no mannitol in it.
Peptide Blend
One vial holding two or more compounds pre-mixed at a fixed ratio by the supplier, as against a stack, where each compound has its own vial. A blend's certificate reports each component separately and states no single purity for the vial.
Enteric Coating
A polymer film on a capsule or tablet that holds together in stomach acid and dissolves at the higher pH of the small intestine. Oral peptide formulations use it to get past gastric proteases, with limited success for anything but short sequences.
Cold Chain
The unbroken temperature-controlled path a material travels from manufacture to storage. Lyophilised peptide is typically held at -20C and solutions at 2 to 8C, and a break in the chain is not visible in the vial afterwards, which is why shipping records matter.
Sonication
Applying ultrasound to a liquid to speed dissolution or disperse aggregates. It appears in laboratory sample-preparation procedures, and prolonged or vigorous application can itself degrade a sensitive peptide.
Sterile Water
Water that has been sterilised and contains no preservative. Nothing in it inhibits growth once the container is opened, which is the single difference from a preserved solvent and the reason the two are not interchangeable.
Water for Injection
A pharmacopoeial grade of water held to published limits on endotoxin and conductivity, supplied preservative-free. The grade describes the water, not the container, and preparations made from it carry no preservative of their own.