SPI Supplies® Brand TEM Grids
To clean or not to clean TEM grids before use
Introduction:
For those doing TEM work, which means using TEM grids, to clean or not to clean has been
a hotly contested question for years. Some researchers routinely go through lengthy
cleaning procedures, with acetone or other solvents, in order to enhance specimen
adhesion to the grid. Others by-pass this cleaning step completely and get
completely fine results.
Most of the leading manufacturers of TEM grids made from copper, nickel, and gold,
give the grids as a final step before inspection and packaging into vials, a
passivation treatment that retards the oxidation of the metal surface. We don't
know if such a treatment has any real benefit on gold grids but for copper and
nickel, such a treatment prevents for some years the formation of the surface
oxides that tend to interfere with specimen adhesion to the grid.
On the other hand, many doing immunogold work on nickel grids tend to use an
acetone cleaning step more often than other users of TEM grids.
Now having said all of that, we have found that customers often times "discover"
vials of grids in drawers that could have been sitting in those drawers for years.
No one really knows the age of the grids in those vials. But it is not unusual
for someone to "discover" a mother lode of grids left over from some ancient
projects, the vials and the labels don't "look" thirty or thirty five years old,
so they use them and then find that they have problems with specimen adhesion.
These are either grids that were made before the passivation treatment was being
used or else, they could be grids that eventually oxidized since the effect of the
passivation treatment was never expected to last forever.
So if you have received fresh grids from SPI Supplies, since we do enjoy a rather
huge "turnover" of grids, you can always be assured of receiving "freshly made" grids.
If you are using copper, nickel, or gold grids, in general, they should not require
cleaning before use. But if you experience adhesion problems, by all means, try an
acetone cleaning treatment so determine if this makes the problem disappear.
SPI Supplies offers a variety of other grids made in other metals such as molybdenum,
tungsten, aluminum, etc. These too should not, in the general case require a washing
step prior to use. But in the event you do experience such problems, then by all means,
subject them to an acetone washing and determine if that improves adhesion.
For severe specimen adhesion problems, we recommend two possible approaches for a solution:
1. Immerse the grids in a solution of poly-L-lysine and once dried, there should be
a noticeable improvement in adhesion, or when sections are involved,
2. Use the Coat-Quick™ G Grid Coating Pen
to enhance adhesion.
We hope this information might be helpful for anyone who has been experiencing specimen adhesion problems
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Tuesday May 13, 2008
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