Any ice sitting on the bottom of your tubes is therefore going to be a problem. Techniques avoiding the use of optical reading are being developed but right now they are at early stages and you can be ‘locked in’ to a specific suppliers consumables – there are no open standards. However the ‘ice problem’ is simple to resolve with some methods that are cheap and easy to implement.
There are a number of techniques that we use that have a reasonable measure of success; using a small stiff brush to scrape off excess ice, using an alcohol spray to ‘dissolve’ the ice and we have even seen a specialist instrument designed just to clear the ice away.
However, the technique we think works best just uses some simple items that you will probably find in your laboratory – a small plastic storage box, some sponges and a bottle of alcohol.
- Put a sponge into the bottom of the storage box and then add alcohol. You don’t want the sponge to be swimming in alcohol, but you do need it to be saturated.
- Then take your rack and push it into the sponge; you need to get the alcohol soaking the bottom of all the tubes.
- Then remove the rack from the storage box and gently tap it onto another dry sponge. This is to remove any excess alcohol from the rack as you don’t want it to drip onto your scanner.
- Check that there are no ice crystals remaining on the bottom of your rack and then you can put it onto your scanner.
You may need to make some variations on the above if you are using racks with any ‘special’ characteristics. For example, those of you that use cryoboxes will be aware that the tubes tend to be held relatively high in the box, this is where you need to look at the sponge ‘softness’ if the tubes are recessed you need a ‘softer’ sponge and if they are close to the base you need a ‘firmer’ sponge; in addition you will need to make sure that the sponge and storage box are large enough for your 9x9 or 10x10 containers.
This will allow you to scan your racks quickly and efficiently. We have often thought about making a product for this but it is just as easy to pop to your local store and buy a sponge and plastic box!