I have used ordinary "kitchen" model microwaves to do complete
decompositions in microwave transparent Parr bombs. I have even used
ordinary Pyrex glassware for the container. Naturally these machines
were not designed to be used in corrosive atmospheres but they only
cost about $100 US which is a small fraction of what commercial lab
units cost. I got about 6 months for moderate use (10-20 samples per
week). The wiring started to corrode so we disposed it and bought a
new one (using petty cash). If you try this approach obtain a full
power unit with a carousel. If you get serious about using these I
have thought that spray painting the internal components with an epoxy
based paint may extend the life of the unit but I am not sure of this.
The bombs are expensive . I remember them to cost about $500 each
from Parr. I do not think there is anything special about commercial
oven type units except for there durability and programmability
(which is special to some) but for this you pay dearly. If you have
the time to develop a slower (one at a time) method you are limited to
the size of the ordinary microwave oven.
Another unit I particulary liked was the Prolabo. (I think it is sold
and distributed under other names as well). The unit I tried focused
the microwaves on the sample rather that bounce them around a cabinet.
I do not mean to leave other manufacturers out but this is my personal
experience. I am sure the commercial closed vessel ovens work great
on some samples but I had my "challenges" with early versions on
polymeric samples. It can get messy and dangerous in closed vessel
Finally, I have done hundreds-thousands of sulfuric acid digestions
in the Tecator block digestor (about $6000) US and found it to compete
well with microwave for polymeric samples. Load up about 24 samples
and forget about it for a day or so. You can also use quite a bit
more sample material than you can with closed vessel bombs and you
don't have to compromise on replicates and blanks because of time.
The long tubes act as condensers when a capped with a glass funnel.
These are commonly used for Kjeldahl digestions.
Yes, I am aware of analyte loss in open vessel digestions so we know
to use internal standards for critical elements.
______________________________ Reply Separator
Subject: Microwaving very large Samples
Author: "Friedhelm vonBlanckenburg" <SMTP:[log in to unmask]> at chicago1
Date: 11/15/1999 8:03 AM
Does anybody know of a microwave system that is capable to take very large
reaction vessels; that is to decompose tens of grams of silicate with
further tens of grams or more of HF ?
Friedhelm v. Blanckenburg
University of Berne