Problems with Sulfur at Agilent 5110

I had to measure sodium and sulfur in smbs today.
At a dilution of 1:10,000, I had the correct reading of about 24% for sodium, but sulfur was incredibly high!
Theoretically, I would have found 500 % sulfur.
I measure sulfur at 181.972 nm radial and calibrate at 10 and 100 mg/l.
The calibration looks really fine. The "boost" rinse is on.
Does anyone have an explanation for this?
Could it have to do with the composition of the smbs?

Thanks for help, Gaby

  • Hi Gaby, I think maybe I know what is happening here. Just googled SMBS = Sodium Metabisulphite, and you are getting a very high and impossible result for sulphur. If the sulphur is forming a gas in the spray chamber i.e. it is a volatile form, then it makes gas and you get 100% transfer of S to the plasma, whereas if the sulphur is in a non-volatile form such as SO4 then it aspirates like other elements and roughly 5% goes to the plasma and 95% down the drain. In this way it is possible to get a result way too high for sulphur. I have seen this with volcano water which was yellow and smelly, the ICP found over 100% sulphur in the sample. I think the only solution is to oxidise it and turn it to SO4, with nitric acid taking care not to lose the sulphur as gas. This would be sample pre-treatment of course, I'll be interested to hear how you get on with this.

  • Hi, thank you for your fast response.

    What you say sounds logical.
    We don't normally work with volatile substances, so we haven't had that problem yet.

    Since this was a one-time sample, we used a different method for sulphur determination.
    We titrated with sodium hydroxide solution.

    Thanks a lot for your help.

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