Dear Vemparala,

Vial breakage has a number of potential causes:

1. it could be a "bad" batch of vials, even if the OD of the vials is a little high, the internal pressure in the tray band will be higher, the vials will be forced together. The glass could be thinner, or just more variable.

2. the upstream process could be damaging the glass - scratches, chips all sever to weaken the glass

3. inconsistent freezing - gives you heterogeneous samples that perform in a different way, homogenious freezing has been shown many times to reduce vial breakage - so look for a process like ControLyo to help eliminate this.

4. Mannitol! Mannitol is the devil for vial breakage, eliminate it! This is because it may, during an annealling step, partially melt and refreeze making very large crystals that swell the cake, giving an internal pressure in the vial.

Hope this provides some places to look.

Kind regards,

Rob

Dear Rob Darrington,

Thanks for your answer; it gave me starting leads to work on. I just wanted to know if you can expand a bit on your points 1 and 3.

1. What is the OD of a vial?

1. And what is a tray band? Is it the railing that surrounds the tray?

3. What kind of heterogeneity are you pointing to? Spatial heterogeneity over the tray/across the trays?

Thanks a lot,

Bharadwaj Vemparala.

Dear Vemparala,

OD = outer diameter of the vial. Note, this may vary up the height of the vial, it is often bigger where the base of the vial joins the side, there may be a bulge.

Tray band = ring surrounding the tray of vials. This has a fixed size. If you have a full tray and need "force" the vials to fit in the band, not uncommon, it is ideal to have a tight pack of vials, just not "too" tight. However much "too" tight is!

Heterogenity = unless you control ice nucleation, all the vials will freeze at a different time. You will then have different ice crystal structures in each vial. The vial that cools more before freezing will have small ice crystals and the vial that cools less will have larger ice crystals ... you then do not have the same condition across your vials, they are different.

A full webinar on freezing from a true expert can be viewed here:

https://www.spscientific.com/Webinars/Archives/

Look for the 2018 webinar by Dr Margit Giesler;

The Freezing Stage in Freeze Drying: Fundamental Concepts 2.0

You will have to register to view, but there is no charge.

Kind regards

Rob