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  • orginial dilution?

    Would the oringial dilution be:
    0.540/715 * 100/10 * 100/10 or have I missed something out as I keep getting the wrong answer.
    Last edited by Msocpharm; 29, January 2009, 10:01 PM.

  • #2
    Re: orginial dilution?

    no one

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    • #3
      Re: orginial dilution?

      Average tablet weight = 12.7592/20 = 0.63796g
      0.1733g in total 200ml - take 10ml filtrate, so would contain (8.665x10^-3)g, and make up to 100ml. Take another 10ml filtrate and make up to 100ml.
      Now you have (8.665x10^-4)g in 100ml.
      Beer lambert law: A = A(1%,1cm) x path length x conc(g/100ml)

      0.540 = 715 x 1 x conc
      Therefore conc = (7.55 x 10^-4)g/100ml.
      This is conc of paracetamol ( maybe) in 100ml, and you have powdered tablet mix conc of (8.665 x10^-4)g, so I think answer is

      (7.55x10^-4)/(8.665x10^-4) x 0.63796 = 0.555868205g = 556mg

      Again I'm not 100% on the answer but i think this is it
      http://i620.photobucket.com/albums/t...snroses2-1.jpg

      ”We are real. We are not glam sh*t or anything else. We are Guns N’ Roses.”

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      • #4
        Re: orginial dilution?

        the answer is spot on
        Last edited by Msocpharm; 29, January 2009, 10:02 PM.

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        • #5
          Re: orginial dilution?

          You might have missed out the 4x dilution factor at the beginning ? Powdered mass added to 50ml then made up to 200ml (4x dilution factor) ??
          http://i620.photobucket.com/albums/t...snroses2-1.jpg

          ”We are real. We are not glam sh*t or anything else. We are Guns N’ Roses.”

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          • #6
            Re: orginial dilution?

            similar qu but what confuses me is do you find mass in 3ml first or 50ml, if its 3ml then surely mass would remain same in 50ml.
            Last edited by Msocpharm; 29, January 2009, 10:02 PM.

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            • #7
              Re: orginial dilution?

              Originally posted by Nikolai View Post
              A
              This is conc of paracetamol ( maybe) in 100ml,
              and you have powdered tablet mix conc of (8.665 x10^-4)g, so I think answer is
              can we always use this method though, why find conc in 100ml?

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              • #8
                Re: orginial dilution?

                Originally posted by Msocpharm View Post
                Noscopine Linctus (16.9249 g) was diluted to 100 ml with 0.05M HCl and 3 ml of this solution was then diluted to 50 ml with water. A 2-cm layer of the resulting solution was found to have an absorbance of 0.561 at the maximum at 310 nm.
                The weight per ml of the linctus was 1.229 g ml-1.
                Taking 90.7 as the value of A(1%, 1cm), calculate the mass (mg) of Noscopine in a 5 ml dose of the linctus.

                similar qu but what confuses me is do you find mass in 3ml first or 50ml, if its 3ml then surely mass would remain same in 50ml.
                Yes you find mass in 3ml and yes it's the same if you make up to 50ml because you're not adding any drug. However you need to take into account the resulting dilution factor in subsequent calculations.
                http://i620.photobucket.com/albums/t...snroses2-1.jpg

                ”We are real. We are not glam sh*t or anything else. We are Guns N’ Roses.”

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                • #9
                  Re: orginial dilution?

                  Originally posted by Msocpharm View Post
                  can we always use this method though, why find conc in 100ml?
                  Yes - because the conc answer you get from Beer lambert calculations has the units of g/100ml
                  http://i620.photobucket.com/albums/t...snroses2-1.jpg

                  ”We are real. We are not glam sh*t or anything else. We are Guns N’ Roses.”

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                  • #10
                    Re: orginial dilution?

                    Originally posted by Nikolai View Post
                    Yes - because the conc answer you get from Beer lambert calculations has the units of g/100ml
                    so i should always work out the conc using beer lambert law and then divide that value by dilution value?

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                    • #11
                      Re: orginial dilution?

                      Originally posted by Msocpharm View Post
                      20 Paracetamol Tablets (total weight 12.7592 g) were crushed and powdered. 0.1733 g of the powder was added to 50 ml of 0.1M sodium hydroxide, diluted with 100 ml of water, shaken for 15 minutes and then sufficient water to produce 200 ml was added. The resulting solution was filtered and 10 ml of the filtrate was diluted to 100 ml with water. 10 ml of the resulting solution was added to 10 ml of 0.1M sodium hydroxide followed by dilution to 100 ml with water. A 1-cm layer of the resulting solution had an absorbance of 0.540 at the maximum at 257 nm. Calculate the mass (mg) of paracetamol in a tablet of average weight, taking 715 as the value of A(1%, 1cm) at the maximum at 257 nm.

                      Give the result correct to the nearest mg.

                      Would the oringial dilution be:
                      0.540/715 * 100/10 * 100/10 or have I missed something out as I keep getting the wrong answer.

                      Can I just ask, what year are you in?

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                      • #12
                        Re: orginial dilution?

                        Originally posted by Msocpharm View Post
                        so i should always work out the conc using beer lambert law and then divide that value by dilution value?
                        In general yes but regarding the paracetamol q you don't.
                        http://i620.photobucket.com/albums/t...snroses2-1.jpg

                        ”We are real. We are not glam sh*t or anything else. We are Guns N’ Roses.”

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                        • #13
                          Re: orginial dilution?

                          Originally posted by shenzys View Post
                          Can I just ask, what year are you in?
                          why?

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                          • #14
                            Re: orginial dilution?

                            Originally posted by Nikolai View Post
                            In general yes but regarding the paracetamol q you don't.
                            Last edited by Msocpharm; 29, January 2009, 10:02 PM.

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                            • #15
                              Re: orginial dilution?

                              The conc answer you get when using Beer lambert law has units of g/100ml you don't need to rearrange or calculate for any other units.

                              The Beer lambert answer was for paracetamol. The dilutions involved powdered tablet mass which included other things as well as paracetamol.

                              I'm trying my best to explain this but I don't know if I'm getting the point across .
                              http://i620.photobucket.com/albums/t...snroses2-1.jpg

                              ”We are real. We are not glam sh*t or anything else. We are Guns N’ Roses.”

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