competent cells: CaCl2 autoclave vs filter sterilisation - (Oct/08/2012 )

I'm preparing to make competent cells. Is there a reason why some people pefer to fliter sterilise CaCl2 over autoclave? Can CaCl2 be autoclaved?

Thank you

I do filter sterilization.
You might want to look @
http://www.protocol-online.org/biology-forums/posts/18679.html

Thank you. Also, to make 0.1M CaCl2, is it necessary to make the dilution from 1m CaCl2 or can I directly make 0.1m CaCl2? I read somewhere that CaCle concentartions must be prepafed from 1M stock solution.

I just simply prepared 0.1M CaCl2 by dissolving 3.67g CaCl2 (dihydrate, FW 147.02) in 250ml water.

SF_HK on Mon Oct 8 14:51:27 2012 said:

Thats fine.

But how you will make last 0.1M Cacl2 with 15% Glycerol for storing @ - 80^oC?

Its quiety handy to make 1M cacl2 , filter it and store @ 4^oC. For making 0.1 M Cacl2 just dilute it 10 times by adding to autoclaved distill water.

i did both types of sterilization and both also works good.
but usually i did filter sterilization because it saves time

to make 50ml 0.1M Cacl2 with 15% glycerol, I would add 42.5 ml (0.1M Cacl2), 7.5ml 100% glycerol. This is OK?

SF_HK on Tue Oct 9 03:41:55 2012 said:

Not ok.

If you add any solution to 0.1 M it will decrease its concentration. You can consider adding cacl2 to 7.5ml 100% glycerol to make it 0.1M cacl2 with 100% glycerol and add 42.5 ml (0.1M Cacl2). But filtering 100% glycerol then for sterilization will be difficult task for u.

Better make 1M cacl2. then dilute accordingly.

Ok,

Lets say I make 1M Cacl2 (filter sterilise).

to make 200ml 0.1M Cacl2 (+15 glycerol)
- 20ml 1M CaCl2 (filter sterilised)
-30ml autoclaved 100% glycerol
-170ml autoclaved water

Right.

Thank you. I'm just horrible at mathematics.