Osmolarity
Definition
The total concentration of dissolved particles in a solution. Preparations used on living cells are matched to physiological osmolarity, because a hypotonic or hypertonic medium stresses the cells independently of whatever is being tested.
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
Lyophilization
Freeze-drying: the solution is frozen and the water removed by sublimation under vacuum, leaving a dry cake whose chemistry is far more stable than the solution it came from. Properly stored lyophilised peptide keeps for years at -20C.
Lyophilized
Freeze-dried. Research peptides ship in this form because a dry powder survives transport and storage that a solution does not, and it has to be reconstituted before any work can be done with it.
Aseptic Technique
The handling practices that keep a preparation from being contaminated: disinfecting a stopper before it is pierced, using a fresh needle, and not touching the parts of the equipment that meet the solution. It governs contamination, not sterility, which a container either had or did not.
Vial
The sealed glass or plastic container a peptide is supplied in, closed with an elastomeric stopper under an aluminium crimp. A single-dose vial carries no preservative and is intended to be entered once; a multi-dose vial carries one so it can be entered repeatedly.
Vial Adapter
A fitting that pierces a stopper once and presents a luer connection, so a syringe can be attached without a needle passing through the closure again. It reduces coring of the stopper on repeated entries.
Aliquot
A measured portion divided out of a larger volume. Splitting a reconstituted solution into single-use aliquots is how repeated freeze-thaw of the whole stock is avoided, and it is the standard answer to a material that degrades on repeated freeze-thaw.
Working Stock
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.
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.