Guidelines for Cryogenic Grinding of Bone in the Freezer/Mill®

Application: Grinding Bone

Introduction

Any plant or animal tissue can be ground in a Cole-Parmer Freezer/Mill, and this includes all bone; fresh or aged, wet or dry. Freezer/Mill grinding vials are immersed in liquid nitrogen (LN) before and during grinding, first to make the sample brittle enough to grind, and then to keep it brittle during the actual grinding. The actual grinding is done by a rod-shaped steel impactor that is magnetically shuttled back and forth between two steel end plugs.

The quantity of sample per load and the size of the sample pieces can heavily affect the grinding efficiency of the mill, particularly with bone, which can be very tough. A simple test is to load the vial, then shake it back and forth to make sure the impactor can move from end to end of the vial. If the sample pieces are too large or there is too much sample in the vial, the impactor can jam or not move far enough to grind effectively. In extreme cases, if the impactor is deflected sideways or wedged against the polycarbonate cylinder by a large piece of bone, the cylinder can crack or break.

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