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Measuring the Correct Dosages in a Bottle. Mg/mL Accuracy.

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  • Measuring the Correct Dosages in a Bottle. Mg/mL Accuracy.

    How is a bottle of steroid or tablet tested for accuracy? Dr. Erik?

  • #2
    How to make a HPLC test

    First of all make an inspection of the equipment in this case the HPLC and see if is working well, if the column is in position and if the desire wavelength is set in the equipment ( the wavelength it is set depending of the active ingredients).

    Second elaborate the mobile phase, this will depend on the active ingredient. There are a lot of different mobile phases but I will give an example. A traditional and common example of a mobile phase is ( methanol / water in a proportion of 70/30 respectively).

    Third elaborate the standard solution
    Weigh 20mg of the active ingredient and dissolve it in 50ml of mobile phase, take 2ml of this solution with pipette and dissolve it in a volumetric flask of 10ml.

    Fourth preparation of the sample (Let say that we will test tablets)
    Weigh 20 tablets and take the average so you can have the weigh of one tablet, after take the equivalent of 20mg of the active ingredient, this can be made with a simple rule of proportion. Example ( if a tablet weigh 150mg and it's contains 100mg of the active ingredient and I need 20mg of the active ingredient of this tablet , I weigh 20 tablets and take the average so I can have the weigh of them after I grind them all in a mortar and take the equivalent in powder of 20mg of active ingredient) after proceed the same as the standard, take the 20mg to a 50ml volumetric flask with mobile phase wait for a few seconds so it can be well dissolved then filter the solution with a filter paper then take 2ml with a pipette and put it in a volumetric flask of 10ml.

    After having the standard solution and the sample ready, we proceed to make the injection to the equipment (HPLC).
    First we inject three times the standard solution and two times the sample after that the chromatography will give us the areas, theses areas has to be averaged, sum the tree areas of the standard and divide them and the 2 of the sample as well. After that divide standard area result / sample area result x 100 = % of purity of the sample

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    • #3
      so is the purity of the sample directly correlated to the mg per tablet? I am trying to figure out exactly how the strength of the medicine is measured. Also for the oils. So, the oils need to be evaporated to get a true measurement of the amount of active ingredient per ml? Or will the purity of the sample give the result?

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      • #4
        No, the purity doesn't have nothing to do with the ammount of mg on tablet or any drug, but the strength is correlated with amont.
        There are three concepts the we have to manage: Purity, quantity and strength.
        Purity of a active ingredient or any raw material comes from how iqual in values is this raw material to the standard
        Amount and strength are correlated because in order to be effective there is a minimum amount that have to reach the receptors.

        in order to know the amount of active ingredient in a oil, if it is a monodrug yes, you can know the amount of active ingredient by evaporating the movil or excipients, but that is not the only way to measure it.

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