Accepted answer
Nobody has published a cycle count, and at 5 mg/mL the concentration tells you what a wrong guess costs: a 0.1 mL aliquot holds 0.5 mg and every microlitre is 5 µg. Damage from freezing is not gradual attrition — it is concentrated at the phase transitions, where ice excludes solute and the unfrozen fraction climbs well above 5 mg/mL for as long as the transition lasts. Two slow cycles can therefore do more than four fast ones, which is why a cycle count is the wrong unit in the first place. The way to make the number one is to make it one: split at reconstitution into single-draw aliquots, label each with 5 mg/mL and the date, and never thaw a container you will refreeze.
The relevant physics is ice-front concentration: as water crystallises, everything dissolved is concentrated into the shrinking liquid phase, including buffer salts.
Buffer salts crystallise at different points during freezing. Sodium phosphate is the classic example: the dibasic form crystallises first and the pH of the residual liquid falls by several units. That pH excursion is the real damage in many cases.
Reported and extrapolated stability by condition
| State | Condition | Usable window | Basis |
|---|
| Lyophilised solid | −20 °C, sealed, dry | 24–36 months | Supplier guidance |
| Lyophilised solid | 2–8 °C, sealed | 12–24 months | Supplier guidance |
| Lyophilised solid | 25 °C, sealed | 4–8 weeks | Extrapolated (Arrhenius) |
| Lyophilised solid | 40 °C, sealed | 1–2 weeks | Extrapolated |
| Solution, preserved | 2–8 °C | 28 days | USP microbiological convention |
| Solution, preserved | 25 °C | 3–7 days | Extrapolated |
| Solution, unpreserved | 2–8 °C | 24 hours | USP microbiological convention |
Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.
Thaw slowly at room temperature or in the refrigerator rather than in warm water. Rapid warming creates local thermal and concentration gradients that promote aggregation.
Condensation onto cold lyophilised material on opening is a recognised handling error and is the basis for the equilibrate-before-opening rule.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Let a frozen vial reach room temperature before opening, or you condense water into it.
Adding a vote because this deserves more of them. – kwn_analytical 37 days ago Adding for future readers: the domestic leg after delivery is the part you control. – Dr_Lena_Ostrowska 3 months ago add a comment