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Calculating toxicant concentration

  1. Apr 15, 2009 #1

    In my lab we're preparing a toxicity bioassay using nitrate (NO3-) as the test toxicant. The tests we're doing are range-finding tests, to help determine the lethal concentration (LC50) for that species with nitrate.

    We are following the lead of another work (http://www.sciencedirect.com/scienc...erid=10&md5=172b82c36ff657803f003c89ddaca62d") which used sodium nitrate (NaNO3) as the source of nitrate. In that article, the test concentrations used for a similar species range from 5 to 160 mg NO3-N/L. This is where my understanding of chemistry is lacking. I'll try to illustrate my doubts with an example:

    If I want to find the LC50 for a solution of 10 mg nitrate/L, what do I calculate exactly?
    a) 10 mg of NaNO3
    b) 13,71 mg of NaNO3 - corresponding to 10 mg of NO3-
    c) 60,71 mg of NaNO3 - corresponding to 10 mg of N

    My feeling is that b) is correct, but the notation NO3-N is throwing me off. Can anyone help out with this?
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Apr 16, 2009 #2


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    I thought it was b) too, lucky thing I asked a friend who's an environmental microbiologist.

    It's c). "NO3-N/l" should be read as 'Nitrate nitrogen per liter". So it's just the amount of nitrogen.
  4. Apr 16, 2009 #3
    Thank you very much alxm! You stopped my day from becoming the new season of 24.:smile:
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