[neal_mcg]

Hi everyone,

Hoping I can get some advice, in the current setup I am are running (ELAN 9000) I have noticed that the Blank before calibration has a high amount of Iron present, an intensity of almost 120000. This stood out to me so I looked back at our blanks for the past 3 weeks and they have gradually increased from an intensity of 60000(the blank value at our validation, which remained steady for almost 5 years).

I have changed the cones, tested blank water from various deionised water sources and also tested with different manufacturers of the nitric acid I spike all my samples with. The internal standard is consistent throughout so it isn't as a result of this. My worry is that if it continues to increase is will affect my LOD and therefore my reporting limit may be compromised.

Any help offered would be greatly appreciated.

Thanks

[Corribus]

Have you tried an optima grade water, or another source that has a certified low iron content?

[neal_mcg]

Hi,

Thanks for the reply, the deionised water we use is certified to have low level iron, as is the other source of deionised water we tested, the water we normally use has been fine for the past 5 years but since the 23rd of October the iron content has gradually begun increasing.

[Corribus]

Is the iron level increasing in all your samples, or just some of them?
Have you swapped out all your glassware (nebulizer, torch, etc.) and tubing?
What is your blank in which you are seeing iron increase - just water?

It is also possible you have some sort of environmental contamination. Iron is a very common element. Have there been any other changes in the lab recently? (Construction nearby, new instruments installed, etc.)

[neal_mcg]

Hi,
Sorry for taking a while to reply.

The Iron has increased in the Blank but doesn't seem to have increased in our Standards or samples. I have changed all the tubing, replaced the oil, cleaned the cones and filters. I haven't changed the glassware yet, but this may be the next step we take. I was thinking it could be outside contamination as we are across the road from an active dock and some of the freighters transport scrap metal, this activity has increased in the past few months so it may interfering.
My blank is deionised water and nitric acid to form a 1% HNO3 solution, however having checked with various lot numbers of this acid and various water sources I have ruled out the acid and water as the source of the issue.

I think my next step will be to clean the glassware so thank you for your advice to do so!!

[Corribus]

If the iron level has increased in the blank but not in your standards, I don't see how it could have anything to do with your tubing or other instrumental components (sample introduction side). On the other hand you say you ruled out the water source, so what else is there? It's got to be one or the other. Have you tried a validated water source as a blank (like, optima grade water).

I know how troublesome it can be to locate contamination of common elements. For a while I was trying to do ICP-AES analysis of silicon and we were getting a persistent background. We tried everything to get rid of it, even bought an expensive Telfon spray chamber and torch. Nothing worked. Eventually (after a year of banging our heads against a wall) we just gave up and outsourced the analysis to someone else.

[stdacet]

It can be possible that the glassware that is used to store or that comes in contact with blank may be the source as exposure to nitric acid can lead to metallic leaching after long exposures.