Chromatography Forum

Hello, I have questions about IPA, NH4OH analysis using ICP/MS.
We have agilent model(7900 model) in our laboratory.

During analysis of IPA and NH4OH with intersection sequence, I found serious sensitivity reduction and data unstable for various metals.
Especially, when I analyze NH4OH sample, next IPA data is not good.
I think NH4OH may affect IPA analysis due to different matrix.

Can anybody recommend good comments to solve these problem for me?
Also recommend good devices for sample pre-treatment.

I'm looking forward to hearing from anybody~~~~~.
Best regards.

Lee

Hello Lee,

What is the concentration/% of IPA and NH4OH in the samples that you measure? What is the matrix of your calibration standards and do you use internal standards (online addition?)?

Most likely you will have quite different transportation effects and nebulization efficiencies for samples and calibration standards, besides the usual matrix effects.

J

Hi, Jerole,

Thanks for your reply for my questions.

Here are my answers.
IPA is undiluted solution and NH4OH is 31%.
Calibration standard is 0.5% HNO3 base.

Do you have any reommendations for pre-treatment?

I'm looking forward to hearing from you.

Lee

You're running 31% dissolved solids through an ICP-MS? Really bad idea; dilute your sample and take advantage of the sensitivity of the instrument. In general ICP-MS should be limited to <2% dissolved solids if possible.

Straight IPA is going to give you problems in your torch; you'll need to set up torch conditions specific to an oxygenated solvent and then calibrate in IPA. Your torch conditions absolutely are not the same for IPA as for dilute ammonium hydroxide.

I'm assuming you are neutralizing the NH4OH? Not a great idea to run relatively strong base through your nebulizer and then follow it with organic solvent! Of course, it WILL be nice and squeaky clean.

An ICP-MS is NOT an AA; you have to match matrices, you have to watch your blanks and solvents, sample pHs need to match, etc.

As Mark said, for ICPMS you have to match matrix of standards and samples. When we have as standard in 1% HNO3 and a sample in 2% HNO3 we will see differences in the response of the internal standards, so they are very sensitive to that.

The Agilent 7900 is capable of running very high dissolved solids if you are using the matrix elimination settings on the torch, but you would still need to have those samples diluted into HNO3 for best results.

For the IPA I would evaporate the IPA then wash the vessel with HNO3 of the same concentration as your standards and run that as the sample. The only element that should give you problems would be Mercury because of its volatility.

We also run samples of NH4OH, but we dilute into water then acidify and digest the samples before running them. This way we have them in the same matrix as the standards which are in HNO3.