Choose the solvent to match the study
The solvent or buffer should be selected for the assay design, not by convention. Most research peptides dissolve readily in sterile laboratory-grade water or phosphate-buffered saline (PBS, pH 7.4); the choice depends on downstream cell culture or biochemical requirements.
This guidance covers laboratory preparation of working solutions only, for in vitro use.
Concentration from vial content, not gross fill
A vial's stated content is the amount of active peptide, reported separately from any non-peptide material. Calculate concentration from the reported peptide content, not from the gross mass of the vial contents, or your working solution will be off.
- Use reported peptide content for concentration calculations.
- Record the exact volume added and the resulting concentration.
- Account for the salt form where the COA reports one.
Aliquoting and freeze-thaw
Prepare a single working solution and aliquot it into single-use fractions before freezing. This avoids repeated freeze-thaw of the master stock, which is the most common cause of avoidable degradation in prepared material.
Documenting for reproducibility
Record the solvent, the reported peptide content, the volume added, the final concentration, and the aliquot date. An assay is only reproducible if the person reading it later — including future you — can reconstruct exactly how the material was prepared.