[Histonet] Cloudy MMA embedded block

[Jack Ratliff]

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.huay <@t> 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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