Cleaning a mortar/pestel

Jim Kami jakami at
Wed May 3 15:18:31 EST 2000

    How clean you need to be depends upon the final use of the DNA. For
RFLP work, we normally grind 5-10 gms of leaves and just wipe the mortar
out with a dry cloth (wet cloth will freeze to the mortar) between
samples. Because we get 50-100 ug of DNA at the end of the procedure, any
contaminating DNA will be so small in relation to the desired sample it's
considered negligible. Also, since we often have to do several hundred
samples at a time, it's the only practical method.
    For PCR based work however, we do use clean mortars for each sample,
since even minuscule contamination might be amplified. (Over the years we
have acquired about 50 mortars so this is still somewhat practical, albeit
a bit slower).
    Two tips: 1) to clean the mortars we wait for them to warm up to room
temp. and then scrub them out with a ScotchBrite pad and 0.1% SDS, rinse
well with DI H2O and dry. Don't autoclave or use a commercial glasswasher.
We have split an awful lot of mortars that way. The thick ceramic can't
handle the temp changes for some reason.
2) If you pre-chill the mortar and pestle in a -80C freezer for an hour or
two, you don't have to keep adding LN2 to keep the tissue cold. Makes a
lot less mess when the ground tissue boils out with the LN2.

Jim Kami                              email: jakami at
Department of Agronomy                Tel: (530) 752-9982
Hunt Hall Rm 272                      Fax: (530) 752-4361
University of California
1 Shields Avenue
Davis, CA 95616-8515 USA

      "Why does Common Sense always seem to be the least common sense ?!?"

Lawrence R Hale wrote:

> I am going to try to work with plant DNA for the first time. I will be
> doing a mortar/pestel grind of leaf tissue under liquid nitrogen, as
> specified by the protocol I am following.
> My question concerns the mortar and pestel. What is the correct way to
> clean the mortar and pestel between grinds so that I don't contaminate
> one sample with tissue from another?
> Thanks,
> Larry Hale, Univ. of PEI
> lhale at
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