Accepted answer
Nobody has published a cycle count, and at 20 mg/mL the concentration tells you what a wrong guess costs: a 0.1 mL aliquot holds 2 mg and every microlitre is 20 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 20 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 20 mg/mL and the date, and never thaw a container you will refreeze.
Start with how many cycles are actually planned, because one or two are immaterial and ten are not.
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.
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.
Count cycles, not degrees. The cycle is the damaging event.
5Two lots stored differently, reassayed at a year — the difference was smaller than I expected. – sian_llewellyn 4 months ago 4Confirming that opening a cold vial in a humid room is a genuinely bad idea. – m_haraldsen 3 months ago add a comment