How to accurately quantify Boron in ultra-pure water?

[joelyue]

I am looking for methods to quantify trace Boron levels in ultra-pure water using ICP-MS. Can anyone point me in the correct direction?

[sassman]

Should be relatively straightforward in ultra pure water matrix. Make some standards and go. Do you have experience with ICP? My table of polyatomic interferences shows Carbon-12 as an interference for boron, but I wouldn't think that would be much of a problem in ultra pure water. I have never actually tried it though, maybe someone has more practical experience?

[H2Oh]

I run boron on an ICP OES and can usually get pretty consistent results down around 50 PPB using a Mod Lichte neb. Sometimes I'll see extremely high results but was told it was related to using borosilicate glassware. I only use plastic volumetric flasks etc to keep consistent standards.

It's pretty straight forward as OES at least.

[jerole]

Boron has two isotopes with the masses 10 and 11. B11 is the most abundant and you should use that mass for quantification by ICP-MS. Therefore, Carbon-12 can't be an interference neither isobaric nor polyatomic.

You should be aware that Boron has a huge memory effect, you will have to rinse long time after your last standard before running the samples, especially at high concentration levels.

[joelyue]

Thank for your input guys. What is this memory effect of Boron? How will it affect my standards when i do calibration on ICP-MS? How will it affect my sample results?
Also how would i know if i have eliminated this memory effect before i run my samples?

[sassman]

Boron has two isotopes with the masses 10 and 11. B11 is the most abundant and you should use that mass for quantification by ICP-MS. Therefore, Carbon-12 can't be an interference neither isobaric nor polyatomic.

I realize that we would not expect C12 to interfere with B11; however, I am looking at a table of polyatomic interferences that lists C12 as an interference for B11. Next to C12 it says "spread". Not sure exactly what that means, but a ref is given (Clin. Chem. 1991, 37, 210-215) if you are interested.

[joelyue]

C12 interference is not an issue to me because i am not expecting any contamination that is organic in nature.

[jerole]

I realize that we would not expect C12 to interfere with B11; however, I am looking at a table of polyatomic interferences that lists C12 as an interference for B11. Next to C12 it says "spread". Not sure exactly what that means, but a ref is given (Clin. Chem. 1991, 37, 210-215) if you are interested.

I had a look at the paper, I guess they meant that the instrument had poor resolution, this is not an issue with the instruments nowadays.

Concerning the memory effect, Boron tends to volatilize as boric acid from the sample solution layer that covers the inside surface of the spray chamber. If you rinse with an alkaline solution you can reduce that memory effect. If you write me at the email below I can send you a paper about Boron determination with ICP-MS where they use a special mixture to eliminate the memory effect.

[joelyue]

Thanks Jerole. Please send it to joelyue@asiamail.com