SPEX SamplePrep 6875 Freezer/Mill Series, Руководство по эксплуатации, Страница: 22 / 42

6875 Freezer/Mill
Page 22 of 42 SPEX® SamplePrep LLC DEC 2015
6.2 Loading Samples into Freezer/Mill Vials (Cont’d)
Your own pprocedure for specific materials should be determined by trials; in practice almost no
two materials grind alike.
In practice, the optimum parameters (sample weight and size, precooling time, grinding times
and number of cycles, impactor rate, etc.) are customized to match particular samples. Your own
procedure for your own materials should be determined by trials; in practice almost no two
materials grind alike. Avoid overfilling vials as this greatly reduces grinding efficiency.
If at first the sample doesn’t grind as intended, try these strategies:

Reduce the overall weight of the sample.

Reduce the size of the individual pieces to ¼ or 1/8 inch (6 to 3 mm).

Increase the precooling time. (20 minutes of precooling is about the maximum necessary
for most samples to reach LN temperatures.)

Grind longer. (30 minutes of actual grinding time is the maximum recommended for one
run, due to the LN capacity of the tub, but you can top off the LN and repeat the run if
necessary.)
Table 1 - Typical Sample Sizes
Sample Large Vial
6801, 6803,
6871
Mid-Size Vial
6881, 6883, 6885
Small Vial
6751, 6761,
6771, 6781S
Microvial
6757
Plant tissue, bone,
muscle, etc. 20-50 g 5-20 g 2-5 g 100-300 mg
Polymer pellet 10-20 g 2-10 g 1-2 g 50-100 mg
6.2.2 Size of Sample Pieces
The size of sample pieces is important. For uniform results, most samples should be cut into
pieces smaller than ¼ inch (6 mm). Very tough samples such as fresh bone should be cut smaller,
down to ⅛ inch (3 mm). There are several reasons for this:

The more irregular the size of the sample pieces, the more difficult it is to predict the
results. Uniform procedures work better with uniform samples.

Thin fibers and films can be very difficult to cryogrind unless they are cut into small pieces
first. Wads of long fibers and crumpled balls of film take up extra room and can be elastic,
even at LN temperatures.

Tough samples in large pieces can be very difficult to grind, and in rare cases may damage
the vial. A large, wedge-shaped piece of bone or a tough polymer can act as a wedge to
push a moving impactor through the side of the polycarbonate tube.