Acceptable / typical background levels
Posted: Mon Apr 29, 2019 1:45 pm
Hi all,
Just for fun (and since I'm still learning the instrument), I ran a solution of 18.2 M Ohm dH20 with EVERY channel / parameter enabled to see what it looked like. The results are below:
Those are dual counts in solution mode.
Things I've learned from this (and other reading / learning):
1) The Ar dimers are a natural "byproduct" of the plasma.
2) We always seem to have some iodine and lead in our system.
3) Xe is present in Argon tanks and tends to increase towards the end of a tank.
4) The instrument cannot distinguish between isotopes of the same mass.
5) The method to make a best guess of which isotope is responsible for a signal is to look at the abundance of both the isotope and the element.
For example, the Ba/Xe 132 signal is most likely Xe because:
a) There are other "pure" signals from Xe.
b) 132 is one of the common isotopes of Xe.
c) Ba mostly exists as 138 and a 132 signal would therefore only be a result of Ba if also accompanied by a VERY high Ba 138 signal.
d) The La/Ce/Ba 138 signal is almost certainly Ba because it's the most common isotope for Ba. Ba is also more common on earth than La and Ce (in addition to La and Ce being very rare in 138 form).
So I guess my questions are:
1) Given this is the "cleanest" signal I'm likely to see, what's an acceptable level of background from other contaminants when running samples?
2) If there is a high level of some isotope, but it's not enabled, is it still contributing to detector aging?
3) How much of a concern is detector aging?
Just for fun (and since I'm still learning the instrument), I ran a solution of 18.2 M Ohm dH20 with EVERY channel / parameter enabled to see what it looked like. The results are below:
Those are dual counts in solution mode.
Things I've learned from this (and other reading / learning):
1) The Ar dimers are a natural "byproduct" of the plasma.
2) We always seem to have some iodine and lead in our system.
3) Xe is present in Argon tanks and tends to increase towards the end of a tank.
4) The instrument cannot distinguish between isotopes of the same mass.
5) The method to make a best guess of which isotope is responsible for a signal is to look at the abundance of both the isotope and the element.
For example, the Ba/Xe 132 signal is most likely Xe because:
a) There are other "pure" signals from Xe.
b) 132 is one of the common isotopes of Xe.
c) Ba mostly exists as 138 and a 132 signal would therefore only be a result of Ba if also accompanied by a VERY high Ba 138 signal.
d) The La/Ce/Ba 138 signal is almost certainly Ba because it's the most common isotope for Ba. Ba is also more common on earth than La and Ce (in addition to La and Ce being very rare in 138 form).
So I guess my questions are:
1) Given this is the "cleanest" signal I'm likely to see, what's an acceptable level of background from other contaminants when running samples?
2) If there is a high level of some isotope, but it's not enabled, is it still contributing to detector aging?
3) How much of a concern is detector aging?