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Dilution in digest sample

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  • Dilution in digest sample

    I need to make a 0.1% dilution in a sample that need to be digested before I can run metals. I'm not sure if I can digested and then make the dilution or if I can make the dilution first and then digested. Anybody can help me in this?? Thanks!!

  • #2
    Originally posted by Paloma View Post
    I need to make a 0.1% dilution in a sample that need to be digested before I can run metals. I'm not sure if I can digested and then make the dilution or if I can make the dilution first and then digested. Anybody can help me in this?? Thanks!!
    I'm not sure I understand what you are trying to so. Is this any more than a 1000:1 dilution by using 1 L of solvent to dissolve the soluble salts in a 1 g powdered solid sample such as soil?

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    • #3
      Yes, it's. But I use small amounts like 50 ml to make my digested sample. And I work only with liquids.
      My question is if I have to make that dilution before I digested the sample or it's ok make it after digesting it. Do I get the same result? Thanks.

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      • #4
        Kindly help me with converting my percentage glucose concentration to uM concentration. My percentages range from 0.2 to 20%. Glucose molar mass is 198.17g/l. Thank you

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        • #5
          Originally posted by Vincy View Post
          Kindly help me with converting my percentage glucose concentration to uM concentration. My percentages range from 0.2 to 20%. Glucose molar mass is 198.17g/l. Thank you
          What kind of percent, w/w or w/v? Ie., is 10% glucose 100 g/kg or 100 g/L? Why isn't the molar mass of your glucose 180.1559 g/mol, or approximately 180 g/mol?

          If your percentage is w/v, express it as grams per liter, ie, 10% is 100 g/L. Divide by the molar mass, this would be 0.555 mol/L or 0.555 M.

          That high a percentage should be expressed as micromolar, but would be 555 000 M. It would be better as millimolar, 555 mM just based on sensible numbers.

          If your percentage is w/w, you will have to consult a table of concentrative properties to convert to w/v. For glucose, there is a table in the Handbook of Chemistry & Physics.

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          • #6
            Yeah pretty high numbers, this glucose we use as standard to extract plant glucose. I was suppose to use the concentration range of 1 μM, 10 μM, 50 μM, 100 μM, 150 μM, 200 μM, 300 μM, 5 ml for each concentration of glucose solution. For this I did it 3 times and the results were negative then I opted for percentages for my standards. I don't know maybe my calculations were wrong, I made 400uM stock solution in 500ml by adding 0.0396g glucose (198.17g/mol). Then my dilutions were as follows; 12.5ul; 125ul; 625ul; 1250ul; 1875ul; 2500ul; 3750ul, respectively. All these were negative did not yield the expected colour change after the reaction. Your help is much appreciated.

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