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PLASMACHEM-L  July 2012

PLASMACHEM-L July 2012

Subject:

Re: MICROWAVE DIGESTION

From:

HERRMANN Otto <[log in to unmask]>

Reply-To:

PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's).

Date:

Fri, 13 Jul 2012 17:31:34 +0000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (109 lines)

You need a high pressure system to do this reliably. Milestone Ultraclave or Ultrawave are most suited for large samples but OK with any system if use 1500 psi vessels. You will have to play with the digestion mixture somewhat. The use of HNO3/HCl will result in pressure generation from the acids themselves, not to mention the H2O2. Try to digest with nitric alone as optimal and if that does not work, first add 1ml H2O2 and 0.5ml HCl and go from there. Depends on the materials in question.

Dr. Otto Herrmann, Ph.D., C.Chem.
Manager, Analytical and Waste Services Dept.,
Kinectrics Inc.,
800 Kipling Ave., Unit 2, KJ135
Toronto, Ontario, Canada 
M8Z 5G5
Phone: 416-207-6262
Fax: 416-207-5550
e-mail: [log in to unmask]


-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Greg Sparrow
Sent: Friday, July 13, 2012 1:06 PM
To: [log in to unmask]
Subject: Re: MICROWAVE DIGESTION

I'd like to use our microwave for our Tissue and Vegetation digestions, but
we need 5g wet (1g dry) of sample in order to achieve our detection limit
requirements.  Most microwave methods I have seen recommend using < 1g wet of
sample.

We tried a few samples and even after a cold digestion overnight, we have
some tube failures and venting.

We currently use 7.5 mL of HNO3, 2.5 mL of H2O2 in a HotBlock for 2 hours,
cool the samples and digest with 2.5 mL of HCl for another hour.

We usually perform a 5 times dilution after digestion before analysis, so the
final concentrations of acid are 3% HNO3/1% HCl.

Regards,

GREG SPARROW, B.Sc.
Trace Metals Supervisor
MAXXAM Analytics
4606 Canada Way
Burnaby, BC
V5G 1K5
 
Office 604 734 7276, ext. Office 8408 or Lab 2157  

Maxxam Analytics - Success Through Science® maxxam.ca

-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's).
[mailto:[log in to unmask]] On Behalf Of Ed McCurdy
Sent: July-13-12 2:42 AM
To: [log in to unmask]
Subject: Re: On line internal standard addition

Hi Craig

Not wishing to scupper your justification for new instrumentation, but for
total levels of those elements, ICP-MS analysis after microwave digestion
should be perfectly straightforward, I think.  Steer clear of hot block if
you want to recover the volatile elements.  Usually organic samples don't
pose much of a problem in terms of dissolved solids, as most of the carbon is
removed during digestion.  So if you work on the basis of a 500x dilution
from the dry sample weight (0.2g digested and then diluted to a final volume
of 100ml), you will be far below the standard 0.2% TDS limit quoted for
ICP-MS.  In fact you should be able to go with much lower dilution than this
(say 200x), if you are pushed on detection limits.

The spectral interferences also shouldn't be too problematic, despite the
fact that you will probably want to add HCl as part of the digestion mix (to
give a level of about 0.5% HCl in the final solution you run).  The HCl will
help a lot with the Hg stability and recovery.  The ArCl and CaCl on As will
be removed effectively in He mode on the cell, and the other potential
interference (such as MoO on Cd) should also be reduced (this will of course
depend on the relative concentrations of Mo and Cd in your seaweed). 

If there is carbon left in your sample digests, you might want to add some
extra carbon to all the samples and standards as well, to equalize the
ionization enhancement effect on As.  Usually adding 2% of some solvent like
IPA, methanol or ethanol gives a consistent effect for all samples.

Best regards

Ed

________________________________________________________________
Ed McCurdy
ICP-MS Product Marketing
Agilent Technologies UK Limited
Phone: +44 (0)1270 878126
VoiceMail: +44 (0)118 927 5373
Fax: +44 (0)161 492 7171
TelNet: 317 5373 (voicemail only)
E-mail: [mailto:[log in to unmask]] Agilent Technologies UK Limited,
Registered Office: 610 Wharfedale Road, IQ Winnersh, Wokingham, Berkshire,
RG41 5TP - Registered No. 03809903 P SAVE PAPER - Please do not print this
e-mail unless absolutely necessary
________________________________________________________________



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This transmission contains information which may be confidential and which may also be privileged.  It is intended for the named addressee only.  Unless you are the named addressee, or authorized to receive it on behalf of the addressee, you may not copy, use, or disclose it to anyone else.  If you have received this transmission in error, please contact the sender.  Thank you for your cooperation. 
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Kinectrics Inc.  800 Kipling Avenue, Unit 2  Toronto, Ontario, Canada  M8Z 5G5

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