LISTSERV mailing list manager LISTSERV 16.5

Help for PLASMACHEM-L Archives


PLASMACHEM-L Archives

PLASMACHEM-L Archives


PLASMACHEM-L@LISTSERV.SYR.EDU


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

PLASMACHEM-L Home

PLASMACHEM-L Home

PLASMACHEM-L  September 2011

PLASMACHEM-L September 2011

Subject:

Re: Drift in Pb signal

From:

"Chisholm, William (CDC/NIOSH/HELD)" <[log in to unmask]>

Reply-To:

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

Date:

Thu, 22 Sep 2011 13:58:12 +0000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (93 lines)

Hello Ed,

That's a good point about the relative abundances of the Pb isotopes.  And your suggestion about skipping the rinse cycle also is good.  Unfortunately, we're nearly out of argon and out of money until the new fiscal year starts up in October,  but as soon as we get enough argon we'll give these a try.

Many thanks,  - Bill

-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Ed McCurdy
Sent: Thursday, September 22, 2011 9:45 AM
To: [log in to unmask]
Subject: Re: Drift in Pb signal

Hi Bill

A simple test to see if it's sample intro would be to sit the probe in one of the problem samples and then measure the same sample several times using your current method (with 6 replicates for each sample measurement) but without the probe actually moving to the rinse between measurements.  If the problem is due to a chemical effect in the sample intro, the signal should not recover between sample measurements.  If it's caused by the detector, the signal should come back to around the same starting point for each replicate #1 - i.e. the time delay for the rinse and uptake between samples gives the system time to recover to the original sensitivity (which seems to be the case if you see the same signal drift regardless of what the preceding sample was).  Lead is not typically problematic from a chemical stability point of view, but it would still be worth looking at some other elements in the same sort of mass range (Tl, Bi...).

Did you happen to notice (or can you find out) if 80ppb is the point at which the detector changes mode (pulse count to analog)?  If all is well up to 80ppb but the signal drifts when it is above 80ppb, it could be that there's a problem specific to the analog mode.

It's interesting that you see the same effect for all the Pb isotopes.  At 80ppb total Pb, you have about 40ppb equivalent 208, and 20ppb each of 206 and 207 (assuming it's natural Pb).  At half the Pb concentration (40ppb total, at which concentration it sounds as though you don't see the problem) the Pb208 would be equivalent to about 20ppb, so from a detector point of view its signal should behave the same as the 206/207 signals in the higher concentration sample.

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
________________________________________________________________



-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Chisholm, William (CDC/NIOSH/HELD)
Sent: 22 September 2011 13:45
To: [log in to unmask]
Subject: Re: Drift in Pb signal

Karen,  Thank you for the note.   We've been using the auto-tune and default settings, and until we get more familiar with the system we're reluctant to change them, especially since the system works well at lower concentrations for Pb and other elements.



 I'm thinking that the next step is to determine if the issue is chemical or instrumental.  We'll look at some other elements, maybe as chloride salts rather than as nitrates, in the 80 - 100 ppb range and see if they mimic the Pb behavior.  If they do, I would suspect it's a detector problem.  If not, I would suspect a chemical interaction in the sample introduction system.

Anyway,  I do appreciate everyone's comments and suggestions.

- Bill

-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Karen Spaleta
Sent: Wednesday, September 21, 2011 4:38 PM
To: [log in to unmask]
Subject: Re: Drift in Pb signal

could that be a P/A tuning issue with the detector?

Karen J. Spaleta
ICP-MS Research Professional
Advanced Instrumentation Laboratory
University of Alaska Fairbanks
PO Box 755780
Fairbanks, AK 99775-5780
ph: 907-474-5452
fax: 907-474-5163
e: [log in to unmask]



On Wed, Sep 21, 2011 at 11:48 AM, Chisholm, William (CDC/NIOSH/HELD) <[log in to unmask]> wrote:
> We have a new Nexion 300D ICP-MS that we use for analyzing lead and other elements.  Whenever we try to run a sample or standard with more than about 80 ppb lead we get a large drift in the lead signal.  We use the Nexion software to set up a routine that flushes the system and then takes 6 replicate measurements, one right after another.  All six replicates are finished in a few seconds.  For Pb concentrations above 80 ppb, the Pb signal (raw counts) falls with each replicate till the sixth (last) replicate, which is typically half or two-thirds the value of the first.
>
> We see this behavior for all lead isotopes.  The drift is always towards lower counts, and we see it no matter what sample we ran previously, pure water, acid blank, or 100 ppb Pb standard, 5 ppb Pb standard.  But for concentrations much below 80 ppb the signal from replicate to replicate is constant within a percent or less.  We see the drift with ultra-pure Pb standards diluted with ultra-pure HNO3 in 18.2 megohm-cm water, and we see it in complex geological samples with multiple elements in HNO3.
>
> I assume this behavior is not normal;  Does anyone have any idea what's causing this?
>
> Many thanks,  - Bill
>
> William P. Chisholm
> Research Physical Scientist
> NIOSH    m/s L-3030
> 1095 Willowdale Road
> Morgantown WV 26505
> 304-285-5977
> [log in to unmask]<mailto:[log in to unmask]>
>

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003
December 2002
November 2002
October 2002
September 2002
August 2002
July 2002
June 2002
May 2002
April 2002
March 2002
February 2002
January 2002
December 2001
November 2001
October 2001
September 2001
August 2001
July 2001
June 2001
May 2001
April 2001
March 2001
February 2001
January 2001
December 2000
November 2000
October 2000
September 2000
August 2000
July 2000
June 2000
May 2000
April 2000
March 2000
February 2000
January 2000
December 1999
November 1999
October 1999
September 1999
August 1999
July 1999
June 1999
May 1999
April 1999
March 1999
February 1999
January 1999
December 1998
November 1998
October 1998
September 1998
August 1998
July 1998
June 1998
May 1998
April 1998
March 1998
February 1998
January 1998
December 1997
November 1997
October 1997
September 1997
August 1997
July 1997
June 1997
May 1997
April 1997
March 1997
February 1997
January 1997
December 1996
November 1996
October 1996
September 1996
August 1996
July 1996
June 1996
May 1996
April 1996
March 1996
February 1996
January 1996
December 1995

ATOM RSS1 RSS2



LISTSERV.SYR.EDU

Secured by F-Secure Anti-Virus CataList Email List Search Powered by the LISTSERV Email List Manager