Aliquoting peptide stock solutions
Why aliquot, how to size aliquots, which tubes to use, how to label and thaw, and why batch numbers belong on every tube.
Aliquoting is the habit that separates laboratories that get consistent results from a peptide stock over months from those that see drift after a fortnight. It takes five minutes at reconstitution and removes freeze-thaw damage, cross-contamination and most of the guesswork about shelf life. This note is the practical routine: how to size aliquots, which tubes to use, how to label, and how to thaw. All Alphex products are for laboratory and in-vitro research only.
Why aliquot
- Each aliquot is thawed once, so freeze-thaw damage stops being a variable.
- The bulk stock is never repeatedly opened, so contamination and evaporation stop being variables.
- Every experiment draws from an identical, dated unit, so results across weeks are comparable.
- If one aliquot is compromised, the rest are not.
Sizing
Work backwards from the assay. If a session uses 40 µL of stock, aliquot 50 µL: enough for the session plus pipetting loss, small enough that nothing significant is discarded. If sessions vary, make two sizes. Avoid volumes under 20 µL in standard tubes, where evaporation and adsorption become proportionally large; if you need tiny amounts, aliquot a larger volume of a more dilute intermediate instead.
Tubes
- Low-protein-binding polypropylene, 0.5 mL or 1.5 mL, screw-cap or snap-cap. Peptides adsorb to ordinary plastic; see low-binding tubes and adsorption.
- Amber for light-sensitive compounds, GHK-Cu above all, or store clear tubes in a closed box.
- Sterile, from a fresh bag, handled with gloves.
The routine
- Reconstitute as in the step-by-step method and let the solution stand until completely clear.
- Label the tubes before filling: compound, concentration, diluent, date, batch number, initials. Freezer-proof labels or a solvent-resistant marker.
- Dispense with a calibrated pipette, low-binding tips, one tip per aliquot if sterility matters. Cap each tube immediately.
- Place in a labelled freezer box; write the number of aliquots and the batch on the box lid.
- Freeze at -20 C. Do not use the freezer door.
- Record it in the lab book or inventory: how many, where, from which vial and batch.
Using an aliquot
Thaw at room temperature or in the hand, invert gently to mix, spin briefly, use. Discard the remainder; do not return it to the freezer. If a partially used aliquot must be kept, refrigerate at 2-8 C and use within days, and note that it has been thawed.
Batch tracking
Every Alphex vial carries a batch number that matches its Certificate of Analysis. Carrying that number onto every aliquot label and every lab-book entry means any result can be traced back to a specific chromatogram and mass spectrum. It costs a few characters per label and it is what makes a laboratory's peptide work auditable. See why COA batch matching matters.
Frequently asked questions
How long do aliquots last?
Months at -20 C for the short peptides in the catalogue when thawed once; see how long reconstituted peptides last.
Can I aliquot the lyophilised powder instead?
Not accurately; freeze-dried peptide is a low-mass, hygroscopic solid. Reconstitute the vial and aliquot by volume.
Is it worth aliquoting a 5 mg vial?
Yes. The value of the vial is in the reproducibility of what you do with it, not the mass.
Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.
Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.
Published 7 August 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.