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Laboratory practice session 03

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    THERMAL ANALYSIS IN LEADING PHARMACOPOEIAS. MELTING POINT DETERMINATION OF API

    I. Questions and tasks for discussion:

    1. What is Thermal Analysis? What types of thermal analysis are described in the pharmacopoeias: Ph. Eur., JP, USP?

    2. What quality levels of drug products can be examined by means of these methods?

    3. What is the difference between the common and differential type of thermal analysis? Describe the main advantages and disadvantages.

    4. Figure the general view of the thermoanalytical curve.

    5. Characterize DSC method. How does DSC differ from the DTA?

    6. Comment the use of TGA for determination «loss on drying», «loss on ignition», «water content», «residue on ignition ». Figure thermoanalytical curves corresponding to each of them.

    II. Analytical work with pharmacopoeial general chapters «Melting point» (as an indicator of the quality of API).

    Examine the proposed Eur. Ph., JP, Int. Pharmacopoeial general chapters – «Melting point determination». Complete the table.

    JP Ph. Eur. Int. Ph.
    1. Capillary method is applied for easily dispersible crystalline substances… 1. Capillary method 1. Capillary method
    2. Open capillary method (both ends of the capillary are open) is applied to substances such as fats, fatty acids... 2. Open capillary method 2. Open capillary method
    3. Drop point 3. Instantaneous method -
    - 4. Drop point -

    III. Lab practice:

    Determine the melting point of one of the proposed APIs. According to the results of the test fill in the form:

    Melting point determination of API by capillary method:

    Normative document (ND)

    2.2.14. MELTING POINT – CAPILLARY METHOD __________

    Testing sample __________________________________________

    Batch/Lot ______________________________________________

    Manufacturer ___________________________________________

    Limits _________________________________________________

    Apparatus and materials:

    1. Instrument ___________________________________________
    2. Capillaries ___________________________________________
    3. Sample bottle _________________________________________
    4. Desiccator with desiccant _______________________________
    5. Glass tubes ___________________________________________
    6. Mortar and pestle ______________________________________

    Procedure description:

    Find in Eur. Ph.

    2.2.14. MELTING POINT – CAPILLARY METHOD
    Test results
    № capillary with sample Tmeas., °С [T bar] , °С Δ = Tmeas – Tcert.,°С
    1      
    2  
    3  

    Δ – temperature measurement error in the heater unit, °C;

    Tcert.. – certified reference standard melting point specified in the enclosed certificate, °C.

    Conclusion: ____________________________________

    IV. Self-test:

    1. In accordance with JP melting point is the temperature at which ...
      1. liquid and solid phase of a substance are in an equilibrium.
      2. a solid sample is completely melted, ie transferred to the liquid phase.
      3. there is a sharp jump in enthalpy ΔH in ΔH – T curve.
    2. The melting point determination is used in drugs quality control for ...
      1. API identification tests.
      2. evaluation of purity of API (impurities limit tests).
      3. evidence of chiral purity of drug substance.
    3. In accordance with JP there are methods to determine the melting point for …
      1. substances those purity is comparably high, which can be pulverized and soluble in water.
      2. substances are insoluble in water and hardly dispersible – fats, fatty acids, waxes, waxes.
      3. paraffin and petroleum.
      4. the nature of the substance does not matter.
    4. JP Method 1 for melting point determination ...
      1. is applied for those substances of which the purity is comparably high and which can be pulverized, soluble in water.
      2. involves the use of thermometer with an immersion line.
      3. involves the use calibration high-purity substances: acetanilide, aсetofenitidine, caffeine, sulfanilamide, sulfapyridine, vaniline.
      4. involves the use of thermometers with different temperature ranges: 40–100, 90–150, 140–200, 190–250, 240–320 °С.
      5. involves different accuracy in different temperature ranges – from up to ± 0,5 ± 1,0 °С.
    5. JP Method 2 for melting point determination ...
      1. is applied to substances, that are insoluble in water which can not be pulverized such as fats, fatty acids, paraffin or waxes.
      2. involves the use of open capillary.
      3. pre-melting the substance at the lowest possible temperature, substance should be placed in ice for 1 hour or stored at temperatures below 10 °C during the day.
      4. pre-heating the substance to a temperature of about 5 °C below the expected melting temperature, followed by heating at a rate of not more than 1 °C/min.
    6. JP Method 3 for melting point determination ...
      1. is applied to substances such paraffins or waxes.
      2. use of vessel with liquid, in which sample with a thermometer are placed, and a heating vessel.
      3. pre-heating to 30 °C at a rate of 2 °С per minute, and further heating at a rate of not more than 1 °С per minute.
      4. implies melting point is temperature at which the first drop of the sample leaves the thermometer.

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