Advice Sought: Plant Nutrient Analysis

Warren Gold warreng at u.washington.edu
Mon Jan 24 14:58:10 EST 1994


SEEKING ADVICE ON DIGESTION PROCEDURE FOR DETERMINING
TOTAL N AND P IN NON-VASCULAR PLANT TISSUES

We are using a wet oxidation procedure for digesting samples
of a cryptobiotic soil crust prior to colorometric analysis for total N & P.
These samples are a mixture of mosses, lichens, fungi, and
cyanobacteria.  The procedure we are using is a lithium
sulfate / hydrogen peroxide / sulfuric acid digest solution
with selenium added as a catalyst (Parkinson and Allen 1975;
Comm Soil Sci Plant Anal 6:1-11).  This procedure has worked
fine for samples of vascular plant tissues and even soils
but we are having difficulties with our crust samples.  We
find that when temperature is increased during digestion, at
a certain threshold, the solution will foam vigorously and
we lose some of the solution/sample out of the tubes.  We
have tried using ethanol drops (and air) to break up the
foaming and a more gradual temperature increase.  All of
this helps, but not much - the procedure is stretching out
for many many days.

Does anyone have some advice for us on this problem and/or
experience with this wet oxidation procedure?  Many thanks
in advance. Please e-mail me (Warren Gold) at:
warreng at u.washington.edu



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