ICP-MS method for sulfur

I've been asked to develop an IPC-MS method for sulfur content in a pharmaceutical drug substance. We have an Agilent 7800 G8421A system. Based on my preliminary literature search it appears development for such a method may be difficult . Would appreciate suggestions. regards,

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  • Hi Kurt. I analyse sulphur all the time. However, in my case in oleochemicals.

    Typically I will digest 0.5 g of my sample with nitric acid in a microwave. Afterwards diluting in milliQ to 50 mL. Keep in mind that some sulphur compounds in your ample may be volatile!

    I use the same ICP as you. I analyze sulphur at mass 32 or 34. Sometimes small amounts are more accurate at mass 34. Sc is the internal standard, and I also use Xe as a collisiongas to remove O2 interference. (Xe is required, without it you can't measure S). Maybe instead of Xe you can add O2 to your plasma gas so that SO ifs formed. And then you can analyse mass 48. But if your samples contain significant amount of Ca and/or Ti this mass can be problematic.

    Like this I can measure approx 20 ppb in solution. Because I am stuck with a dilution factor for the samples of 100, my LOQ is approx 2 ppm S in the sample.

    For very low amounts of S (in my case 2- 10 ppm) I will also add a significant amount of IPA to my ISTD solution. This will slightly elevate the S signal and so decrease detection limits.

    Hope this helps. Good luck!

  • carwogill,

    Thank you for the prompt reply.   This is very encouraging especially the LOQ level you've obtained as I was hoping just to detect down to 25 ppm.

    From your comments, it appears if I switch out the He collision gas for Xenon on our system I should be able detect S and hopefully develop an acceptable method.

    Do you know if switching to Xe is as simple as changing the tank?    Will the gas flow need to be adjusted for Xe to optimized S detection?

    Greatly appreciate your help.    thanks again    

  • Please confirm if your system has the H2 cell upgrade which allows you to use Xe

    thanks,

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  • We have an ICP system (7800) with a heliumline, a H2 line and a third line for an optional gas, which in my case is Xenon.

    I don't remember if a third gasline was standard or optional for the 7800 ICPMS. And I don't know if it is possible to attach a Xenon cylinder to the fixed He and H2 lines. For that you should probably contact an Agilent engineer

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