Chromatography Forum

Hello!

Feel free to tell me to remove the post as it relates to ICP-MS, but I was curious if anyone had a good document or source on isotope ratio measurements? I've been asked to collaborate on a project doing these types of measurements and never have before. We're looking to analyze water and wood samples for carbon isotopes.

I found this article that uses our instrument, a Perkin Elmer NexION2000 with Syngistix software.
https://resources.perkinelmer.com/lab-s ... ratios.pdf

I've done some research and know that you need to use isotopically certified standards, and that quad ICP-MS systems don't have as good of precision as MC-ICP-MS, but that's as far as I've gotten. The screen of our software's isotope ratio method editor is below (differs from the boron paper just for demonstration):



I guess I'm just confused on what the reference mass is (maybe from the isotopically certified standard) and the corrections? I know about mass bias from reading but not actual experience. Also, would I just select the other isotope I'm interested in and use the same reference mass and corrections?

The whole project only came about because word got around that I repaired our mass spec (LC-MS, QQQ and posted about in here actually) - we historically have never had one here, and then received the ICP-MS as a non-recurring budget request.

Thank you to anyone who can take the time to help!

Corrections on ICP-MS are usually used to correct for other metals that produce interfering masses. Such as if you have a target with a mass that is exactly 16 different from another target, if the plasma produces an oxide then it can interfere with the first target, but if you know how much of the second is present you can subtract that amount from the first signal and compensate for it.

It has been a while since I ran our ICP-MS but Agilent hands out a periodic table type chart that has all the possible masses of each element listed in rows of 16 mass wide, so that if you have a target mass you are looking for you can look directly above it and see if there is an element that will interfere as an oxide. You can also have interference of Argides, Nitrides, Chlorides, other Halides, and some doubly charged masses, such as if you have an element with a mass of 82, if it becomes doubly charged it will appear as 41 and if you have an element with mass 41, it would interfere with that one.

Your software should have some help files describing how this works in your specific system. Also EPA methods 6020 and 200.8 have some discussion on these correction factors.

Hello,
I don't think that your post does relate so much to ICP-MS. If I was asked to measure the carbon isotopes of wood, I would assume that the desired precision would specify Isotope Ratio Mass Spectrometry (IRMS). There are a number of labs dotted around the world who can provide this service, usually using a combustion analyzer to convert solids to CO2. Same with the "Carbon isotopes of water" by which I would assume is meant the carbon isotope ratio of dissolved inorganic carbon. This is measured by acid evolution of CO2 into a helium headspace. CO2 is then measured in a triple collector MS for 12CO2, 13CO2 and 12CO18O has a specialised preparation system for the task. the oxygen isotope ratio of the water itself is accessed by a very similar method. If "carbon (of water)" refers to dissolved organic phases then it's a little trickier, preferably using specialised preparation equipment, but again is provided as a service from a small number of labs around the world.
I could provide suggestions for contract labs if required.
I hope this is of some help

Hello!

Feel free to tell me to remove the post as it relates to ICP-MS, but I was curious if anyone had a good document or source on isotope ratio measurements? I've been asked to collaborate on a project doing these types of measurements and never have before. We're looking to analyze water and wood samples for carbon isotopes.

I found this article that uses our instrument, a Perkin Elmer NexION2000 with Syngistix software.
https://resources.perkinelmer.com/lab-s ... ratios.pdf

I've done some research and know that you need to use isotopically certified standards, and that quad ICP-MS systems don't have as good of precision as MC-ICP-MS, but that's as far as I've gotten. The screen of our software's isotope ratio method editor is below (differs from the boron paper just for demonstration):



I guess I'm just confused on what the reference mass is (maybe from the isotopically certified standard) and the corrections? I know about mass bias from reading but not actual experience. Also, would I just select the other isotope I'm interested in and use the same reference mass and corrections?

The whole project only came about because word got around that I repaired our mass spec (LC-MS, QQQ and posted about in here actually) - we historically have never had one here, and then received the ICP-MS as a non-recurring budget request.

Thank you to anyone who can take the time to help!

Hello,
I don't think that your post does relate so much to ICP-MS. If I was asked to measure the carbon isotopes of wood, I would assume that the desired precision would specify Isotope Ratio Mass Spectrometry (IRMS). There are a number of labs dotted around the world who can provide this service, usually using a combustion analyzer to convert solids to CO2. Same with the "Carbon isotopes of water" by which I would assume is meant the carbon isotope ratio of dissolved inorganic carbon. This is measured by acid evolution of CO2 into a helium headspace. CO2 is then measured in a triple collector MS for 12CO2, 13CO2 and 12CO18O has a specialised preparation system for the task. the oxygen isotope ratio of the water itself is accessed by a very similar method. If "carbon (of water)" refers to dissolved organic phases then it's a little trickier, preferably using specialised preparation equipment, but again is provided as a service from a small number of labs around the world.
I could provide suggestions for contract labs if required.
I hope this is of some help

Hello!

Feel free to tell me to remove the post as it relates to ICP-MS, but I was curious if anyone had a good document or source on isotope ratio measurements? I've been asked to collaborate on a project doing these types of measurements and never have before. We're looking to analyze water and wood samples for carbon isotopes.

I found this article that uses our instrument, a Perkin Elmer NexION2000 with Syngistix software.
https://resources.perkinelmer.com/lab-s ... ratios.pdf

I've done some research and know that you need to use isotopically certified standards, and that quad ICP-MS systems don't have as good of precision as MC-ICP-MS, but that's as far as I've gotten. The screen of our software's isotope ratio method editor is below (differs from the boron paper just for demonstration):



I guess I'm just confused on what the reference mass is (maybe from the isotopically certified standard) and the corrections? I know about mass bias from reading but not actual experience. Also, would I just select the other isotope I'm interested in and use the same reference mass and corrections?

The whole project only came about because word got around that I repaired our mass spec (LC-MS, QQQ and posted about in here actually) - we historically have never had one here, and then received the ICP-MS as a non-recurring budget request.

Thank you to anyone who can take the time to help!

Very helpful indeed!

What you are being asked to do sounds like carbon dating - that is a specialist application best left to the specialists.