Ooi,
Somehow you are getting moisture/water mixed in with the MMA
solution(s). I only remember visiting the IMCB facility, so if this is
not your facility then I am not sure of your laboratory environment
(air temperature/humidity). The best thing I can tell you at this
point is to try and find ways to reduce the chance for moisture
accumulation.
I am pretty sure that at a minimum you are storing your catalyst and
monomer (MMA) at 4C and your softner (DBP) at room temp. Maybe you
should take extra steps to ensure your chemicals are at room temp
before any use. Lastly, your polymerization is taking too long for
your small 20mL vials. My specimens of similar size require only 3-5
days to completely polymerize. Now, I dont remember your concentration
of catalyst, but if it is around 2.5g/1L embedding solution, try
skipping the 4C step and use room temp (<23C) until the specimens are
polymerized. Then finish them off in the oven when they are tacky or
mostly hard on top. The 4C step is mostly to slow the polymerization
for larger specimens requiring a larger volume of solution and/or when
the lab temp cannot be controlled routinely at or below 23C. The water
bath then also helps to regulate the temperature of the polymerization
in the case where the lab environment is too cool (<20C) and retarding
the rate of polymerzation.
The main thing to keep in mind is that the lab environment pretty much
controls the process and is probably the main variable that will
contrast labs that perform the exact same method.
Jack
On Apr 21, 2009, at 12:33 AM, ooi.ting.h...@nhc.com.sg wrote:
Hi,
I am trying very hard to get a clear MMA embedded block. I am
appreciate
if there is any advice on doing it. I am using 100% MMA (liquid) and
0.5%
Perkadox 16 (powder) to do the embedding. I have tried to embed the
sample
in different conditions. However, it seems to be extremely hard to
get a
clear embedded block.
Below are the methods that I have tried.
1. Before embedding, bring the MMA and perkadox 16 to room
temperature.
After a few mix it by invertion, I aliquot the solution to the glass
vials
that contain samples or simply glass vials that without sample. I
put the
glass vials (both with and without sample) in 4 degree, room
temperature
and even 37degree oven.
2. Mix the MMA and perkadox when it is cold, invert it a few times.
Aliquot it to glass vials that contain sample or without sample. Put
in
4degree, room temperature and 37degree oven.
I have also tried to speed up the polymerization process by using
vacumm
for a few samples...
Throughout all the sample that I have, I only manage to get a clear
empty
glass vial which I put in the 4degree for one month and a clear
embedded
sample which I put in 4 degree overnight and bring it out to room
temperature. The rest of the glass vials (with or without sample) are
cloudy.
I have repeated the methods that I used to get a clear embedded
block, I
did not get any clear block (for both with and without sample).
I am glad if there is any expert advice or guidance. We need a clear
embedded sample. Thank you very much!
Regards,
Ooi
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