Ruth and Hasan,
I see the "dirty" autolens often enough. Usually our enviro samples have
little effect on the system but every so often clients slip in a
particularly nasty batch which will have similar effects to those
described. I think somebody put a similar question to the list a few
months ago only they incorrectly described it as an electronic drift
problem. Some samples will have a "bad" effect on the lens requiring the
lens voltage to be raised to achieve expected counts on optimisation.
This can last for a couple of days until the offending material is
desorbed (long term drift may be evident but 2-3 hr runs should okay).
My instrument logs show clearly when these samples are put through the
system via the lens voltage kicks. I don't see this as a problem for
routine ppb analysis as long as your int stds are doing their job. Read
a new calibration and drive on. I think my ELAN's are fairly tolerant of
this type of rough treatment and is not a cause to stop production, just
keep it in consideration if there are any "funnies" You may want to
rerun some of the subsequent samples a few days later to reassure
yourself. Of course if you want to run several hundred of this type of
sample at a time then you will want to consider a FIAS to reduce the
loading of the sample (matrix) on the MS.
ICPMS Supervising Chemist
From: Ruth Wolf [mailto:[log in to unmask]]
Sent: Tuesday, 30 November 1999 8:12
To: [log in to unmask]
Subject: Re: Insensitive ELAN 6000 , any ideas ??...
I believe you misinterpreted my response. After sometime running dirty
any lens "system" will become dirty and the
lens voltages will need to be reoptimized. As I'm sure you know there
optimum lens setting for each mass. The ELAN 6000/6100
instruments have the unique ability to dynamically scan the lens voltage
the mass, so the lens is always at the optimum voltage (called
As the lens becomes dirty, the AutoLens calibration must periodically be
re-adjusted to optimize the voltage scan range used on the lens.
The symptoms described were typical (in my several years of running the
instrument) of an ELAN needing an AutoLens calibration.
On a side note, AutoLens does have some ability to actually reduce the
suppression caused by space charge effects as reported in
"Determination of Trace Elements in Uranium: Practical Benefits of a
Lens System" by Denoyer, Jacques, Debrah, and Tanner,
Atomic Spectroscopy, Volume 16, No. 1, Jan/Feb 1995.