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<div>Hi Nadav,</div>
<div>The contaminations could be either ice or impurity of ethane, if it’s from ethane, you may heat the holder tip to –150 C to see if the particles evaporate, if not, they are ice.</div>
<div>Such nanometer granule shape of ice contamination seems to be formed in cold air first and deposited onto the cold grid, warmer holder would tend to crystallize original amorphous ice forming the ‘leopard –cubic pattern’ of contamination as Win described.
Minor vacuum leaking into microscope should generate evenly distributed ice coverage and not nucleated ice particles, because the column is at RT.</div>
<div> </div>
<div>There are two places could generate such contamination, most likely, the contamination is from the Leica EM plunger’s grid transfer chamber, the positive pressure from LN2 evaporation is not enough to keep humid air off the chamber; the second place may
be Gatan loading station, if you open the lid to mount the clip ring, wet air can sneak in to contaminate your grids. You may compare with Vitrobot and/or mount a grid with the plastic lid on all the time.</div>
<div>Good luck,</div>
<div>Dan </div>
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<span style="font-weight:bold">From: </span>3dem <<a href="mailto:3dem-bounces@ncmir.ucsd.edu">3dem-bounces@ncmir.ucsd.edu</a>> on behalf of Nadav Elad <<a href="mailto:nadav.elad@weizmann.ac.il">nadav.elad@weizmann.ac.il</a>><br>
<span style="font-weight:bold">Date: </span>Thursday, September 1, 2016 at 5:00 AM<br>
<span style="font-weight:bold">To: </span>"<a href="mailto:3dem@ncmir.ucsd.edu">3dem@ncmir.ucsd.edu</a>" <<a href="mailto:3dem@ncmir.ucsd.edu">3dem@ncmir.ucsd.edu</a>><br>
<span style="font-weight:bold">Subject: </span>[3dem] contamination in cryo samples<br>
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<p class="MsoNormal">Dear all<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We are having a serious contamination problem in our cryo preparations and would be grateful for any suggestion. Although this issue has been discussed in the past in this forum, the solutions raised do not seem to work. The attached image
shows the contamination on a bad day. I am referring mainly to the lighter, smaller particles (10-20 nm) which are the most persistent. They seem to be above or below the ice layer and are the first to evaporate under the electron beam. The concentration of
contaminants is variable. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We are using a Leica EM GP plunger for freezing, and Tecnai T12 and F20 microscopes with Gatan side entry holders. We have tried to replace the ethane cylinder and are in the process of ordering a third one, cleaning the glow discharger
machines, different cryo holders, different cryo-transferring units and grids of varying sources. There seems to be no leaks in the compustages of the microscopes.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you for your help<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Nadav<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">--<o:p></o:p></p>
<p class="MsoNormal">Nadav Elad, Ph.D<span dir="RTL"></span><span dir="RTL"></span><span lang="HE" dir="RTL" style="font-family: Arial, sans-serif;"><span dir="RTL"></span><span dir="RTL"></span>.<br>
</span>Electron Microscopy Unit<span lang="HE" dir="RTL" style="font-family: Arial, sans-serif;"><br>
</span>Weizmann Institute of Science<o:p></o:p></p>
<p class="MsoNormal">Rehovot, Israel<span lang="HE" dir="RTL" style="font-family: Arial, sans-serif;"><br>
</span>Tel: +972 (0) 8 934 2115<o:p></o:p></p>
<p class="MsoNormal">Mobile: +972 (0) 52 3909 420<o:p></o:p></p>
<p class="MsoNormal">Email: <a href="mailto:nadav.elad@weizmann.ac.il">nadav.elad@weizmann.ac.il</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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