7 min read · updated 2026-08-21
Metered Solution Formats: Formulation and Stability
How a prepared solution format differs from lyophilised material, and what that means for stability, preservative content, and analytical records.
What a metered format is
A metered format supplies compound already dissolved at a defined concentration in a container that dispenses a fixed volume per actuation. This is a formulation decision made before the material reaches the purchaser, in contrast to a lyophilised vial, where the purchaser selects the solvent and determines the concentration at the point of reconstitution. The practical difference is that a metered format removes a variable and fixes it: the concentration is set by the preparation rather than chosen by the work.
Solution and lyophilised material are not equivalent
Most peptide degradation pathways require water. Oxidation, deamidation, and hydrolysis all proceed substantially faster in solution than in the dry state, which is why lyophilisation is the standard storage form for material intended to be held. A prepared solution format has therefore already begun the clock on those pathways at the point of preparation. This is not a defect of the format but it is a real constraint: a solution preparation cannot have the shelf stability of the equivalent lyophilised material, and best-by dating for the two should not be expected to match.
Why preservative content is required
A container accessed repeatedly over time admits air and, potentially, microorganisms. A prepared solution intended for multiple accesses therefore requires an antimicrobial preservative, most commonly benzyl alcohol, for the same reason bacteriostatic water carries one. The preservative addresses microbial growth only. It has no effect on chemical degradation, so its presence does not extend the chemical stability of the compound in solution — a distinction routinely conflated and worth stating explicitly.
Concentration as a formulation parameter
In a lyophilised vial, concentration is derived: mass divided by whatever solvent volume is added. In a prepared solution, concentration is stated by the formulation and the dispensed volume per actuation is fixed by the container. Both are calculable quantities but they are established at different points and by different parties. For any work requiring a specific concentration, a lyophilised vial affords control that a prepared format does not, since the prepared format can be diluted but not concentrated.
What the lot certificate covers
A certificate reports measurements performed on the material analysed. Where a published lot record exists for a format, it describes that lot of that format. Certificate coverage is not uniform across formats in this catalogue: vial and nasal preparations carry published lot records, and oral spray and capsule preparations do not currently have published lots. A certificate for one format is not a certificate for another, and the absence of a published record for a given format should be read as absence rather than inferred from records published for a different one.
Storage of prepared solutions
Because the material is already in solution, the handling guidance for reconstituted stock applies from receipt rather than from the point of reconstitution. Refrigerated storage slows chemical degradation but does not stop it; light protection matters for sequences containing aromatic residues; and freeze-thaw cycling should be avoided for the same aggregation reasons that apply to any peptide solution. Unlike a lyophilised vial, a prepared format cannot be returned to the dry state, so the storage decisions available are narrower.
Frequently asked
How does a prepared solution format differ from a lyophilised vial?
The material is already dissolved at a set concentration rather than supplied dry. This fixes the concentration at preparation instead of at reconstitution, and means the solution-phase degradation pathways have already begun.
Why do prepared solution formats contain a preservative?
A container accessed repeatedly requires an antimicrobial preservative, commonly benzyl alcohol. It suppresses microbial growth only and has no effect on oxidation, deamidation, or hydrolysis.
Do all formats have published lot certificates?
No. Vial and nasal preparations carry published lot records. Oral spray and capsule preparations do not currently have published lots. A certificate for one format does not describe another.
Is a prepared solution as stable as a lyophilised vial?
No. Most degradation pathways require water, so material held in solution degrades faster than the same compound held dry. Best-by dating for the two should not be expected to match.
See the practice, not just the principle
Every lot we release is published in full — assay, method, and measured result — and the record stays online after the lot sells out.
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