In article <5d759n$kn6 at mserv1.dl.ac.uk>, RUTH MCMAHON
<RMCMAHON at ollamh.ucd.ie> wrote:
> I was doing an RNA prep, and instead of spinning down
> the precipitated RNA I dried it in the speedivac.
> I am now left with a massive salt pellet.
> Could anyone suggest how to clean this up.
Sodium acetate is quite soluble in 70-80%(v/v) ethanol; RNA (unless it is
extremely salt free) is not. Wash the pellet (and the inside surface of the
tube) with 80% ethanol - cap the tube, vortex vigorously until the pellet does
not seem to be getting smaller, give the tube a 5-10 minute spin (the longer
time for smaller quantities of RNA), and discard the supernatant. Repeat this
process until the sodium acetate is gone. This is effective for sodium chloride
(but to a lesser extent), potassium chloride, and is very effective for cesium
chloride (among others). It is essentially useless for phosphates or sulphates.
This obviously is applicable for DNA pellets, where residual salt can be a real
problem when trying to redissolve DNA. And an additional note, ammonium acetate
is not terribly volatile (as was implied by one poster) and does not lyophilize
easily; it is of course very ethanol soluble and so can be eliminated quite
readily with even 95% ethanol washes.