Physical Pharmacy Lecture 2: Polymorphism of Solids
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Questions and Answers

What is the term for the transition that takes place in one direction only?

  • Pseudopolymorphic transition
  • Monotropic transition (correct)
  • Polymorphic transition
  • Solvate transition
  • How many polymorphic forms of cocoa butter are mentioned in the text?

  • 4 (correct)
  • 5
  • 3
  • 6
  • What is the term for a substance that forms crystalline structures incorporating solvent molecules into the crystal lattice?

  • Hydrate
  • Solvate (correct)
  • Pseudopolymorph
  • Polymorph
  • Why do different solvates of the same drug produce different blood concentrations?

    <p>Due to differences in crystallization processes</p> Signup and view all the answers

    Which form of cocoa butter is best suited for use as a suppository base?

    <p>Stable beta form</p> Signup and view all the answers

    What is the primary difference between solvates and polymorphs?

    <p>Molecular arrangement of the API</p> Signup and view all the answers

    What is a characteristic of polymorphism in crystalline solids?

    <p>Molecules arrange themselves in two or more different ways</p> Signup and view all the answers

    What is a factor that influences the formation of polymorphs?

    <p>Conditions of crystallisation</p> Signup and view all the answers

    Which of the following polymorphic forms has the highest energy state?

    <p>Metastable polymorph</p> Signup and view all the answers

    What is enantiotropic transition?

    <p>The change of polymorphic forms from one to another is reversible</p> Signup and view all the answers

    What is the characteristic of a stable polymorph?

    <p>Lowest energy state and highest melting point</p> Signup and view all the answers

    What is an example of polymorphism in a natural substance?

    <p>Graphite and diamond</p> Signup and view all the answers

    What is the primary difference between hydrates and true polymorphs?

    <p>Incorporation of water molecules in the crystal lattice</p> Signup and view all the answers

    What is the purpose of X-ray diffraction in pharmaceutical analysis?

    <p>To differentiate between solvates and true polymorphs</p> Signup and view all the answers

    What is the primary application of thermal analysis in pharmaceuticals?

    <p>To analyze the physical and chemical changes of materials upon heating or cooling</p> Signup and view all the answers

    What is the primary advantage of using TGA in pharmaceutical analysis?

    <p>It can be used to identify the presence of residual solvents in pharmaceutical materials</p> Signup and view all the answers

    What is the primary difference between amorphous and crystalline compounds in terms of X-ray diffraction?

    <p>Amorphous compounds have no definite peak in X-ray spectra</p> Signup and view all the answers

    What is the primary purpose of DSC and TGA in pharmaceutical analysis?

    <p>To determine the purity and polymorphism of pharmaceutical materials</p> Signup and view all the answers

    Study Notes

    Polymorphism

    • Polymorphism is a property of crystalline solids, where molecules arrange or orient themselves in two or more different ways.
    • Polymorphs have different physical properties, such as melting point, solubility, and X-ray diffraction.
    • Formation of polymorphs depends on the conditions of crystallization, solvent used, rate of crystallization, impurities, supersaturation, and temperature.

    Types of Polymorphic Transitions

    • Monotropic transition: a transition that takes place in one direction only, for example, from a metastable to a stable form.
    • Enantiotropic transition: a reversible change of the polymorphic forms from one to another.

    Properties of Polymorphs

    • Stable polymorph represents the lowest energy state and has the highest melting point and the least aqueous solubility.
    • Metastable form represents the higher energy state and has a lower melting point and high aqueous solubility.
    • Metastable form converts to the stable form due to their higher energy state.

    Cocoa Butter

    • Cocoa butter has 4 polymorphic forms: meta-stable gamma (18°C), alpha form (22°C), beta prime form (28°C), and stable beta form (34.5°C).
    • The stable beta form is best suited for use as a suppository base.

    Pseudo-Polymorphism

    • Pseudo-polymorphism is caused by changes in the crystallization process, which results in the inclusion of solvent molecules in the crystal, producing solvates or hydrates.
    • Solvates or hydrates differ in properties from the non-solvated sample, just like different polymorphic forms.
    • Different solvates of the same drug can produce different blood concentrations from the administered solid oral dosage form.

    Solvates and Hydrates

    • Solvates: crystalline structures in which solvent molecules are incorporated into the crystal lattice, exhibiting different physical properties compared to the anhydrous form.
    • Hydrates: crystalline forms of a substance in which water molecules are incorporated into the crystal lattice, affecting properties such as solubility and stability.

    X-Ray Diffraction

    • X-ray diffraction method is used to differentiate between solvates and true polymorphs by changing the temperature.
    • Amorphous compounds have no definite peak in X-ray spectra.

    Thermal Analysis

    • Thermal analysis methods are used to characterize the physical and chemical changes of materials upon heating or cooling.
    • Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are commonly used methods.
    • Thermal analysis is important for the determination of purity, polymorphism, moisture content, amorphous content, and stability.

    TGA (Thermogravimetric Analysis)

    • TGA is used to measure residual solvents and moisture, and can also be used to determine solubility of pharmaceutical materials in solvents.
    • Analysis of pharmaceutical materials is a large area of application for thermal analysis.
    • Three types of thermogravimetry are used.

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    Description

    This quiz covers the physicochemical characteristics of drugs, focusing on polymorphism in crystalline solids. Learn about the different physical properties of polymorphs, including melting point, solubility, and X-ray diffraction. Test your knowledge on the formation of polymorphs and their conditions.

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