PREPARATION OF GEOLOGICAL AND GEOMICROBIOLOGICAL SPECIMENS FOR TEM EXAMINATION BY EMBEDDING IN LIQUID SULFUR
We find, as do others (Joswiak, D.J. 2003), that the greatest difficulty in utilizing this technique is solidifying the sulfur block without cracking. To properly solidify the block, (a) the liquid droplet must be extremely small, (b) the embedded material must occupy a relatively small fraction of this volume, (c) the droplet must be melted to just above its 119°C melting point, and (d) solidification must proceed slowly. Another difficulty in preparing these samples is handling the solidified block. To minimize handling and contamination problems, we solidify the block directly onto a rod designed to fit into the ultramicrotome.
For microbial specimens, the technique yields good results for certain experiments. The technique is most useful, however, for carbon-bearing mineral specimens. We present TEM images of several different specimens prepared with these methods, and compare TEM carbon analyses with specimens prepared in traditional resins.
References:
Bradley, J. P., L. Keller, et al. (1993). Carbon analyses of IDPs sectioned in sulfur and supported on beryllium films. 24th lunar and planetary science conference. D. Blanchard and D. Black, Lunar and Planetary Science Conference. 24: 173-174.
Joswiak, D.J. (2003) Personal communication.