Sensitivity drop through time in LA-ICPMS

It would be best to remove the introduction from the laser and set it up with the liquid sample introduction.  Change the setting in the software (Tools, Settings, Sample introduction) to use peri-pump instead of laser.

Run it through all of the startup tasks:  Torch Axis, EM setting, Plasma correction, Standard lens tune, Resolution and Axis, and the performance report.  If you are not performing any of these since install, then yes, the EM voltages, torch axis setting, and resolution/axis being off will reduce sensitivity.  Plasma correction and Standard lens tune are only for the performance report.  

Running the 1 ug/L Agilent Tuning solution, the sensitivity varies based on your model.

          The base model                                  #100 (x-lens)                           #200 (s-lens)

Li7        >3800 counts                                >5000 counts                           >20000 counts

Y89      >14000 counts                               >19000 counts                        >120000 counts

Tl 205   >5300 counts                                >7000 counts                          >45000 counts

These are installation specifications.  As long as you are close then it's not the instrument.  It could be the batch settings.  Do you regularly optimize the lens voltages in your batch?  Although you have cleaned them, they are not in the same condition as when new and could require some adjustment to get best signal, and 7-89-205 ratio.  Omega lens and Omega bias will inversely change low and high mass.  So, if you increase Li7 counts with those lenses, Tl205 signal will drop.

Hi Tom Herzog. Thanks very much for the answer.

I run that tunning in liquid mode every week (been told it's unnecesary to do it that often).

It presents enormous variations from one week to another. Bust most of our problems are with mass 7. Sometimes counts are less than 200. We have x-lenses. Masses 89 and 205 are always fine.

For example, mass 7 is, from july till today:

2645 -> 7045 -> 655 -> 7301 -> 251 -> 893 -> 227 -> 190

One thing I have noticed is that lowering "Q1 exit" to a more negative value than the one from the tunning, rises the counts automatically (when working in Laser mode... I never had to try it in solution mode). For example after tunning it, it gives -1, and going to -3 or -4 manually rises all cps. But honestly I don't like doing it because I don't know what that means.

Also extract 1 in -10 gives more cps than in 0.

Thank you for the update.  Extract 1 with x-lens should be zero. In changing Q1 Exit and Ext 1 voltages, you will want to check the background as increasing counts in the standards may also be increasing background counts.

That is a very large variation for Li7.  Are you changing something manually that increases or decreases the counts?  Do you know what was different from the runs where Li7 was near 7000 counts?  If you call up the report it should list the hardware settings, see what is different from that last run with only 190 counts.

Each week are you tuning in the batch, or using the Startup Configuration?  This should be the Startup Configuration that is run every so often.  Torch Axis, EM setting, and Resolution and Axis are global settings that need to be run.  The batch tune will show the torch position H and V values, the EM voltages, and the Resolution/Axis information, but it doesn't optimize them.  These are either optimized with Startup or by manually running them through the Hardware, Dashboard, and some of those Icons that show in the middle of the Dashboard.

If you leave it with Laser as the sample introduction, do you self-aspirate with the nebulizer?  I've not run it this way, does the peristaltic pump run if left in Laser sample intro?  

With the plasma off, run the lens shortage test.  Go to Hardware, Dashboard.  Select the icon in the middle that states Ion Lenses and select Maintenance.  Just above the table on the left, select Shortage Test.  Do they all pass?

Hi Tom. Thanks again for the answer.

Shortage test is OK. everything passes.

That numbers I showed are from the start up tuning, indeed. I run it every week, standard 1 ppb Agilent solution 7 89 205.

Today they are awful, worst than ever. 15 counts of mass 7, and the others also didn't perform well.  I'm going to clean cones and lenses.

Anyway, after that, we run specific batches auto tunings with the same solution plus 1 ppb 208 232 238 (or masses of interest).

I'm going to check from variations from tune to tune, but I don't particulary changed anything between those tunings.

When using the laser, the nebulizer is completely unused. Just a tubing from the ICP with an Ar flow that goes right to the torch.

When all the masses are low, check the nebulizer.  As you don't run it often, it's possible something dried out in it and either soaking it or running dilute nitric/hydrochloric acid mixture will dissolve it.  On the User Tune configuration tab, Click Set Acq Parameters for Sensitivity, scroll down to the first open Numerator cell and enter 12, then next down, 56, and the next down 80.  Start signal monitor.  Those should read 500k to 1 million counts.  If 80 is way over 1 million, this typically is due to little or no solution making it to the plasma so it runs a bit hotter and we see more Ar40Ar40.  If you have one, try a new nebulizer and soak the current one.

Thanks a lot Tom. I tried it slightly different, just as the "sensitivity troubleshootting guide" of Agilent says. (From the queue menu, and aspiring ultrapure water).

12 is 4500 counts and going down, 56 is 70 000 and going down, 80 is 330 000 and going down. Guide just asks if they're "zero" or not.

Problem is next step of the guide. It asks me to run only Resolution/Axis with those masses (12 56 80) and it won't finish successfully.