6875 Freezer/Mill
Page 26 of 42
SPEX® SamplePrep LLC
DEC 2015
6.5 Opening, Emptying, and Cleaning Freezer/Mill Vials
(Cont’d)
The plastic center cylinders for all vials, and the Poly-Vial end plugs and impactor capsules, are
made of polycarbonate.
While this polymer is very tough at low temperatures, it is sensitive to
alcohol, acetone, and other organic solvents, and should be cleaned only with soap and water.
A mild bleach solution will control organic contamination. Polycarbonate can be autoclaved, but
this will weaken it.
Before re-using polycarbonate cylinders,
always
inspect them for cracks or other damage. They
may last for dozens or hundreds of samples, but as soon as they begin to crack they should be
discarded. Liquid nitrogen can enter through cracks and vaporize when vial is removed from
Freezer/Mill. As the vial warms vaporized LN will build pressure and an end plug can pop out
with force so the sample may be lost.
If sample adheres to the steel end plugs and impactor, they can be cleaned with water and soap
or detergent, or with organic solvents. If they must be disinfected or cleaned of any organic
residue, they can be washed with bleach or chemical cleaners or autoclaved, but should always
be dried immediately after use. The steel parts in the 6751, 6801, and 6881 vials are made from
440C Stainless Steel, a magnetic stainless steel, which is corrosion-resistant but may rust to some
extent if left in contact with water for too long. All stainless steel parts should be dried after
washing.
The steel parts of the chromium-free 6771, 6871, and 6883 vials can also be washed, disinfected,
or autoclaved.
Do Not wash with bleach or chemical cleaners.
Chromium-free steel is not rust-
resistant and must always be dried immediately after washing. Store Cr-Free Vial parts in a
sealed bag with a desiccant.
Rust on steel Freezer/Mill parts can be removed by scrubbing them with steel wool or an abrasive
cleanser. If rusting persists, store the parts in a sealed bag with a desiccant.
6.6 Checking the Liquid Nitrogen Level
The LN should be topped off when needed as a matter of routine. If the programmed grinding
cycle includes more than twenty or thirty minutes of actual grinding time, the nitrogen level
should be visually checked at about that point and more added if needed. A cumulative grinding
time of more than thirty minutes per run is not recommended, as after that much grinding the LN
level is close to the point where the LN sensor will shut down the mill. However, if the mill must
be run for an extended time, and the LN sensor stops the grinding program, the mill can be
refilled with LN and the grinding program resumed where it stopped.
The 6875 Freezer/Mill can be refilled automatically with the 6820 Auto-Fill System, which adds LN
to the tub when the LN level is low. The 6820 Auto-Fill System must be installed and calibrated at
our factory. A 6875 Freezer/Mill that was not ordered with an Auto-Fill System must be returned
to SPEX SamplePrep LLC if installation is desired.