Questions and answer Keys : Physical Pharmacy II Unit IV

Questions

2 Marks Questions:

1. Define and explain micromeretics.
2. What is meant by mean particle size?
3. Differentiate between bulk density and true density of powders.
4. Explain the significance of specific surface area.
5. Define and explain porosity in the context of powders.
6. Describe the principle behind the sedimentation method for determining particle size.

5 Marks Questions:

1. Explain the principal and procedure for particle volume measurement using Coulter Counter.
2. Discuss the importance of flow properties in pharmaceutical powders.
3. Enlist and explain in detail densities of particles.
   

10 Marks Questions:

1. Enlist and explain  methods for determining surface area.
   
2. Name and explain  methods for determining particle size.

Answer Key : (Only for reference to write answers in detail)

2 Marks Questions:

1. Micromeretics:

   • Micromeretics is the science and technology of small particles, particularly their size, shape, and distribution in pharmaceuticals.
   • Explanation: Micromeretics deals with the properties of particles at the micrometer scale, crucial in pharmaceutical formulations for ensuring proper dosage and efficacy.

2. Mean particle size:

   • Mean particle size refers to the average size of particles within a sample, calculated by various methods such as microscopy, sieve method and sedimentation method.
   • Explanation: It provides a central value representing the size distribution of particles, aiding in understanding their behavior and impact on formulation properties.

3. Bulk density vs. true density:

   • Bulk density is the mass of a powder divided by its bulk volume, including the inter-particulate void spaces, while true density is the mass of the powder divided by its absolute volume, excluding void spaces.
   • Explanation: Bulk density indicates how tightly packed the particles are in a sample, while true density represents the inherent density of the material itself.

4. Specific surface area:

   • Specific surface area refers to the total surface area per unit mass of particles and is crucial in determining the rate of dissolution, adsorption, and chemical reactivity.
   • Explanation: It quantifies the extent of interaction between particles and their environment, influencing various pharmaceutical processes and formulations.

5. Porosity:

   • Porosity is the ratio of void volume to the total volume of a sample, indicating the presence of void spaces or pores within the particle structure.
   • Explanation: Porosity affects powder flow, compressibility, and permeability, influencing drug delivery systems' performance and stability.

5 Marks Questions:

1. Particle volume measurement using Coulter Counter:

   • Principle: Coulter Counter utilizes the principle of electrical impedance to measure the volume of particles suspended in an electrolyte solution.
   • Procedure: The particles pass through a small orifice, causing changes in electrical resistance, which is then correlated to particle volume.
   • Explanation: Coulter Counter provides accurate sizing and counting of particles, essential in pharmaceutical quality control and research.

2. Importance of flow properties in pharmaceutical powders:

   • Good flow properties ensure consistent dosing, uniform mixing, and efficient manufacturing processes.
   • Explanation: Poor flow properties can lead to content non-uniformity, segregation, and processing challenges, affecting product quality and performance.

3. Densities of particles:

   • Enlistment and Explanation:
     • Bulk density: Mass of powder divided by bulk volume including void spaces.
     • Tapped density: Bulk density after mechanically tapping the powder to reduce void spaces.
     • Granular Density : Mass of powder divided by  volume excluding void spaces between the particles.
     • True density: Mass of powder divided by absolute volume excluding void spaces.
   • Explanation: Understanding these densities helps in predicting powder behavior during handling, processing, and packaging.

10 Marks Questions:

1. Methods for determining surface area:

   • Enlistment and Explanation:
     • Adsorption Method (BET method): Measures surface area by adsorption of gas molecules onto the solid surface.
     • Air permeability Method : The principal resistance to the flow of a fluid such as air through a plug of compacted powder is the surface area of the powder
   • Explanation: These methods provide accurate surface area measurements critical in assessing the reactivity, adsorption capacity, and dissolution behavior of pharmaceutical powders.

2. Methods for determining particle size:

   • Enlistment and Explanation:
     • Optical microscopy: Direct visualization of particles under a microscope to measure size.
     • Sieving method: The Sieving method is a classical technique based on the principle of particle size segregation through a series of sieves with progressively smaller mesh sizes.
     • Sedimentation method: Measures settling rates of particles in a liquid medium to calculate size.
   • Explanation: Each method offers advantages and limitations, influencing their suitability for specific applications in pharmaceutical research and development.