Regarding Spex mills: Spex mills are optimal for grinding biological
samples because the grinding occurs in liquid nitrogen, so that minimal
degradation of the sample occurs. We have used one for several years, and
in my mind they are excellent for grinding biological materials including
bones. There are down sides however. You must have a clean source of liquid
nitrogen. The units are not particularly rugged (wires often become
disconnected), and the grinding containers are a pain in the neck to clean
out. We use them primarily when sample homogeneity is absolutely critical
or with fossil material that otherwise might be friable.

You can't go wrong with one of these, but don't expect high throughput. Not
even the most dogged technician could manage more then a few samples a day
before they were completely bored. We have used the stainless steel tubes.

Marilyn Fogel

Dr. Marilyn L. Fogel, Senior Scientist
Carnegie Institution of Washington
Geophysical Laboratory
5251 Broad Branch Rd., NW
Washington, DC 20015
USA
202-686-2410 ext 2480
FAX 202-686-2419