Loading Samples Into Freezer/Mill Vials - Cole Parmer Freezer/Mill CG-400 Operation Manual

6.1 Adding Liquid Nitrogen Coolant (Cont'd)
If the Freezer/Mill tub is empty, pour liquid nitrogen (LN) into the tub until it is approximately on
third full. Initially LN will boil off vigorously, but as the tub cools the boiling will subside. Add
more LN gradually, to avoid splashing and boiling over, until the LN level is approximately
2 inches below the rim of the tub. When boiling is subdued, push the lid down gently until the
bottom of the latch can be engaged. Pause if splashing becomes excessive. When the vapor
stream has subsided, open the lid again and top off the liquid nitrogen in the tub, filling it to the
mark on the inside wall of the tub. Insert a loaded vial or vials into the coil (if this has not already
been done), and tighten and lock the coil gate.
Press the Freezer/Mill lid closed and latch it. Caution: When the lid is closed and latched,
nitrogen vapor which vents from the Freezer/Mill can displace the oxygen in a closed room and
cause asphyxiation. A grinding program can now be run, as outlined in Section 5.2.

6.2 Loading Samples into Freezer/Mill Vials

6.2.1 Introduction and General Recommendations
Start by choosing a sample that is typical of those to be ground on a regular basis. As a rule of
thumb, the sample pieces should be small enough to circulate inside the vial as the impactor
moves back and forth, and should take up no more than ⅓ to ½ the volume of the vial, with the
impactor in the vial. Typical sample sizes for the different sizes of Freezer/Mill vials are shown
below in Table 1.
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 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. (15 minutes of precooling is about the maximum necessary
for most samples to reach LN temperatures.)
• Grind longer. (20 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.)
1300-87051-1M, REV 6
Cole-Parmer®
CG-400/CG-450 Freezer/Mill
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