[DaftScotsman]

Hoping for some knowledgeable people to help here -

What is the correct / best way for verifying ICP analysis?

Is it through calibration, or through running an Ion Balance check?

Is it possible for the ion's not to balance?

Thanks for help and responses,

DS

[DaftScotsman]

As a follow up:-

Would it be right to say if there was contamination in there, that it might not be possible to calculate an ion balance?

I thought an ICP ran a check for ions, so the solution must balance.

Would it be right to say it’s not the Analytical guys jobs to try to work out what might be “wrong” with a sample but to report what they find. Or should an ICP operator understand that ions must balance (if they should).

[Stepan]

ICP does not test for nonmetals (most anions). You can test all kind of metals plus sulfur and phosphorus. Therefore you cannot do ion balance.

If you need to verify the ICP method, you can do it through analysis of "blind samples" and compare you results against the true metal load. In professional testing there is a set of procedures to verify the performance: Sensitivity check (MDL), recovery check (LCS), precision check (range), calibration verification (ICV), calibration stability (CCV), carry over check (CCB)

In general, analyst reports whatever she/he measured without correction. Project manager reviews the results and may order the review, verification or re-test.   

[MJH]

As previous Forum Members replied, ICP-OES cannot measure things like PO4,2-; SO4,2-; CO3,2-; etc.  It means that it is not possible to perform an ion balance with ICP only.  You require Ion Chromatography (for Cl-, F-, SO4, PO4, CO3) analysis together with ICP analysis to get some kind of ion balance.

Most ICP-OES instruments will be able to measure P and S (not PO4 / SO4), and it could be converted to PO4 or SO4 using the correct factors, BUT it implies that all P and S are in the PO4 or SO4 state, which is not always true.

Some ICP-OES can measure Cl at 133 nm, but F is almost impossible.

[Pradeep]

Use spiked samples. That is the best way.

[osmium]

Hoping for some knowledgeable people to help here -

What is the correct / best way for verifying ICP analysis?

Is it through calibration, or through running an Ion Balance check?

Is it possible for the ion's not to balance?

Thanks for help and responses,

DS

There are companies that can supply "performance qualification" samples.  These will have a certificate that with have an "acceptable range" for the analytes that you are trying to determine. 

You can also spike samples with the analytes before you do any sample preparation and determine the % recovery.  This lets you know if you're losing anything during your sample prep.

-os