I would dry them, grind them, digest them in a sealed bomb (Parr bomb) in HNO3 and then analyze them. Iodine has limited sensitivity by ICP, and you need to avoid the use of other halogenated acids (HF, HCl) due to the presence of trace levels of iodine in them.
Thank you Mark!
We did the analysis on the past using microwave extraction of freeze dried samples with HCL: HNO3 (3:1), it was OK. Iodine level in was quite high, so the sensitivity was not a problem.
Also the main reason of using the acid mix instead of just HNO3 (or HNO3:H2O2, or TMAH) is because we are interested in other elements (mostly heavy metals) as well, so using one digestion for several purposes.
Another question. In your procedure you used dry seaweeds. How did you dry the samples? Did you use dry seaweeds to boost the iodine level? Did you also try to digest wet (as received) samples?
Freeze drying is probably better - we don't have a freeze dryer, so we dried them at 60C. If the iodine is high enough then the use of mineral acids is obviously preferred. We've done work in the past on vegetation where the iodine levels are relatively low, and it has been challenging.
Oh, I see. People use GC-MS for low levels. Freeze drying become not available (for free). In literature mentioned that iodine is highly unstable. So, I think may be with drying we might loose some. I am thinking of using 1 g of the sample as received (well macerated and contained 95 % moisture). Iodine is unstable in acidic media, as well, so might need to stabilise digests with NH4OH raising pH to 9-11. Thanks again for your comments.
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