EtBr Safety / CsCl disposal / recycling

[Ed Rybicki]

> To:            methods-and-reagents at net.bio.net
> From:          metzler at sara.cc.utu.fi

>....... and dump the decontaminated buffer
> or CsCl solution down the sink.


> ...whether it is OK to dump CsCl down the drain.....

YOU DUMP CsCl DOWN THE DRAIN???!!  WHAT SORT OF ECO-CRIMINAL ARE YOU!!!

Seriously, though, CsCl is not exactly environmentally beneficient- and is
EXPENSIVE, at least in this part of the world.

So we RECYCLE it - and it is not particularly difficult, can be done in
bulk, and provides material of sufficient purity for run-of-the-mill
plasmid purifications.  It also postpones the problem of disposal a
while...!

Here from our Departmental Handbook:


             CLEANING-UP CAESIUM CHLORIDE FOR RE-USE;

  Author: Eric O'Neill, Dept. Microbiology, Univ. Cape Town

  The success of this method is dependent on your collecting all
  the CsCl used for density gradient purification of plasmids/
  whatever: to make it worthwhile you need a minimum of +1 litre
  waste, collected in sealed bottles.

  1.   Stir in Merck decolorising charcoal powder (about 3g/litre)
       into CsCl waste: this step removes DNA, RNA and ethidium
       bromide.
  2.   Pass through Whatman's No. 4 filter paper.
  3.   Boil down until CsCl starts to crystallise (USE BOILING
       BEADS!! - IT WILL BEGIN TO BUMP AT THIS STAGE)
  4.   Cool down to room temperature for full re-crystallisation.
  5.   Pour off mother liquor (this is brownish due to
       caramelisation of Tris/whatever).
  6.   Redissolve in de-ionised water, repeat re-crstallisation
       steps 1-5.
  7.   Dry crystals: under vacuum if possible.

  THIS IS NOW READY FOR USE AS PLASMID-GRADE CsCl: crystals may
       need grinding to reduce their size for easier handling

  8.   Return mother liquor to next batch of waste CsCl.



  ____________________________________________________________________
 | Ed Rybicki, PhD             |       "Lord, won't you buy me        |
 | (ed at micro.uct.ac.za)        |                                      |
 | Dept Microbiology           |         A Mer-ce-des Benz..."        |
 | University of Cape Town     |                                      |
 | Private Bag, Rondebosch     |                                      |
 | 7700, South Africa          |           - Janis Joplin             |
 | fax: 27-21-650 4023         |                                      |
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