[batteryshill]

Hello, I would post this in the graduate/professional subforum but that doesn't seem to get much in the way of posts.

I do vacuum filtration through gooch crucibles as part of my work. We pick up graphite and teflon particles on the filtering medium, which we then need to quantify. So we then pass the crucibles in a muffle furnace at 900C, which burns off the teflon and leaves the graphite, so we can get these values gravimetrically.

We have run out of the fiber frax/aluminosilicate fibers used as the filtration medium. The only place I can this material for sale is here (http://www.sigmaaldrich.com/catalog/ProductDetail.do?N4=06416|FLUKA&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC&lang=en_US#) but it is backordered until early March, and we need something before then. The last order of these filtering fibers was from 1995, by someone who is long retired. Is there a suitable replacement that can be muffled, or another supplier that has these? The glass filter disks burn off at 500C.
We also analyze the filtrate for trace metals so we cannot use anything metal based as a filter.

[Stepan]

Why wouldn't you use quartz filters? I have a few packs of them in stock. Diameter 37 mm, nominal pore size 1 micron. They are actually used to elemental carbon analysis. 

[batteryshill]

Hmm, these may work. I need 21 mm. Do you have any? Who are you with?

[Stepan]

I am a distributor of this media in Canada:

http://www.lcsairtest.com/sampling-media/particulates/filter-membranes.html

Quarts is not there, because it is not very common. I will add it to the list later. For my clients: 37 and 25 mm are the standard sizes. I may be able to find 21 mm. Do you want to buy 37mm to try?

[Stepan]

Why wouldn't you use PVC or similar membranes instead of alumosilicate. They are ashless (<50ug of ash).
http://www.lcsairtest.com/sampling-media/particulates/filter-membranes/pvc-membrane-37mm-100.html

As you burn PTFE off your sample, PVC will be burnt as well. In result you have a pure graphite sample, and can test it for metal content. Affordable and no trouble with bulky equipment.