I have worked with microwaves before and if you use a closed vessel
microwave then you will not have to worry about anything blowing up. CEM
out of North Carolina has a closed vessel microwave unit call the MES 1000
or 200 with has safety devices on it that cuts the machine off when the
pressure becomes to great for the vessel to handle. In addition to this it
can hold 10-12 vessels at a time and each vessels can hold ten grams or
more. Just wanted to put that out there for consideration.
At 10:30 AM 11/15/99 -0500, Scott W. McGeorge wrote:
>This is very dangerous advice. Big samples can blow up big time. Despite
>monitoring the degradation of the oven, the real issue is the built-in
>safety mechanisms of laboratory systems.
>Very best regards,
>Scott W. McGeorge
>Transition Technologies Inc.
>3044 Bloor Street West, Suite 605
>Toronto, ON, M8X 2Y8, Canada
>[log in to unmask]
>Transition Technologies is the Canadian Distributor for:
> Transgenomic Inc. molecular biology workstations
> CETAC Technologies elemental analysis instruments
>----- Original Message -----
>From: Bondarowicz, John <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: 15-Nov-99 9:56
>Subject: Re: Microwaving very large Samples
>> Dear Friedholm,
>> 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
>> based paint may extend the life of the unit but I am not sure of
>> 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
>> 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
>> I do not mean to leave other manufacturers out but this is my
>> 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
>> 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.
>> John Bondarowicz
>> ______________________________ 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