I am about to order some new Kel-F sheets to make the septa used to seal 
the Wheaton 1mL vials used on our Micromass multiprep, for doing 
carbonates and oxygen in water. 

In this setup the needle is pushed through the blue silicone septum and 
the Kel-F disc.  I am concerned about the number of times the needle, 
instead of punching a neat hole through the Kel-F, actually punches a 
wad into the vial.  When I take the cap off the vial there is an annulus 
of Kel-F between the rim of the vial and the silicone septa and a disc 
of Kel-F inside the vial.  (I hope that makes sense.)  This used to 
happen occassionally with carbonates, where the needle is large and 
pretty blunt, but now it is even happening with the smaller water needle.

We have been using sheets 0.005" thick.  I'm wondering whether this is a 
dud batch of Kel-F or is the Kel-F too thin.  What thichness do other 
labs use?  I'm also interested in which suppliers are the best.  Post 
comments about suppliers off-list if you prefer.



David Wheeler

Professional Officer
Geochemistry Laboratory					
School of Earth and Environmental Sciences        			
University of Wollongong,               
Wollongong, 2522, NSW          		

Phone   02 4221 4586 (office)
	02 4226 5903 (lab)
Fax 	02 4221 4250 

E-mail	[log in to unmask]

'These days, if a scientist can't get
 an answer by isotope analysis, he ain't hep'

                       - Isaac Asimov, 1959