ICP-OES Intensity Loss

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RyanATC
RyanATC's picture
ICP-OES Intensity Loss

We have been seeing a persistant problem with our intensities dropping as runs progress. We have seen as much as 25% drop in intensity during the run (measured by difference in QC and CCV readings, as well as from one calibration to the next). Our instrument details are as follows:

Varian 715-ES ICP-OES (now owned by Agilent)
Radial torch
Sturman-Masters spray chamber
V-groove nebulizer

So far, we have tried changing out torches, spray chambers, nebulizers, and tubing without any success. The instrument is recalibrated every 40 samples, with a QC and CCV after each calibration and before the next recalibration. We have run check samples in various spots throughout the runs, and it appears that the drop is gradual and constant through the entire run. We recently began using an internal standard (Y), which is compensating for the loss, but the loss is still there.

Agilent has been unable to help us, and we would like to avoid a service call if possible. Has anyone else seen this problem? Any suggestions to hellp minimize the effects?

BenjaminWWT
BenjaminWWT's picture
We are also having the same

We are also having the same problem.
 
Using the Optima 8000 ICP-OES (PerkinElmer)
Radial Torch
Quartz Spray Chamber
PFA-ST Nebulizer

We have also have changed out all parts thinking that something could be malfuntioning,
from tubing to torch. We even have switched to a Scott Spray Chamber.
Still having problems...

Ths is set in a Waste water treatment facility, the main elements we are testing for are,
Cr,Cu, and Ni. Standard solution is Yttrium 1ppm in a 2% Nitric.
Though your lucky enough to only have to recalibrate every 40 samples, I've been having to recalibrate some times as offen as every 6 samples. Y intensity often starts out at 1.8M in the morning but will sometimes fall as low as 300K in the evening.

Though again, I think it might have to do more so with our torch, within hours of replacing the torch with a new clean one, the torch will have a white build-up on the end. I have yet to find of way to clean it off completly. Even had one explode on me earlyer this week and another last night brake on the bottom end. Service persons don't seem to understand why this is happening ether.

Jesus Murillo
Jesus Murillo's picture
ICP

Are you running waste water directly ?

RobertoBresciani
RobertoBresciani's picture
Optima 8000 ICP-OES

Optima 8000 ICP-OES (PerkinElmer)
axial view
 
We are experimenting the same problem.
We also noticed a "chronic" intensity loss during the whole year: we bought that ICP OES a year ago, and at the end of the first torch alignment the maximum intensity was 13M using a 1 ppb Mn solution. Now we hardly get 8M, so we lost 40% of the intensity in just one year. It seems that the problem got worse during last month.

While the machine initilizes optics, we get a message from the instrument (that we couldn't find in the operation manuals) reporting that "temp/adjustment ratio too high", or we get large values at the end of this process.

We could not fix the problem neither cleaning carefully and changing nebulizer, chamber and torch, nor checking the gas flow.

Does anybody have noticed the same problem or have an idea how to fix it?

LabRatOne32350
LabRatOne32350's picture
We sometimes get the "temp

We sometimes get the "temp/adjustment" also. There is an adjustment that, as far as I know, has to be made by a service person. If the counts go over 100 or less than -100 you will get the error, It is the number of "clicks" that are needed to reset something (prism, grating - not sure what it is) in the optics

LabRatOne32350
LabRatOne32350's picture
The white build up is

The white build up is probably due to devitrification. There is no way to remove it. What are your gas flows? We are finding out that our 8000 isn't able to properly operate at the advertised Plasma flow rate.

Nuke girl
Nuke girl's picture
ICP-OES 8300

We are losing alignment intensities and getting a FIN Temp alarm. I think it is the tub thermistors. But what could be causing the intensity losses on alignments. The Hg align is independent of the torch assembly technically and it has decreased greater than 50%. We replaced the Hg lamp but it is still declining. We also changed the torch assembly consumables just to be sure it wasn't affecting the Mn radial and axial alignments.Does anyone know what could cause the intensity losses like this?  

BlackMetal Chem
BlackMetal Chem's picture
ICP-OES

I have a Prodigy XP ICP from teledyne but I would assume that other systems have the same basic components. When I see intensities start to drop I start with the windows to the optics box. On my instrument the radial window looks like a small glass cylider and the axial is a purge tube with tubing coming off the bottom just after the air knife.  It sounds like you are running a dual view instrument.  Mine is dual view with the torch in in an axial configuration and a small mirror to view the radial spectra.  This mirror is the second place I look.  Both the windows and this mirror can become coated over time and can greatly reduce the intensities if coated or smudged.  Given you are seeing a drop in the Hg I would definatley check the windows and see if that is the problem.  If it is the mirror the peak shapes (radial) when you peak the plasma will look kinda jagged. The mirror can also have a fine coating that you cannot see just by looking so when in doubt I swap it out to see if it helps, and if not keep the old one because it is still fine to use. Just make sure you do not touch the surface and leave finger prints on any of these things and mind where they are positioned before you take them out so that you place the new parts back in the same position (I take pictures before taking anything apart but that is just me) . I hope that helps!