MPharm Particle Size & Shape
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Questions and Answers

Which statement accurately reflects the combustion characteristics of different sized particles in black powder?

  • Fine powder produces less combustion pressure.
  • All particle sizes burn at the same rate.
  • Powders with fine particles can build pressure too quickly. (correct)
  • Larger particles are less powerful than finer particles.

What is the effect of using finer particles in black powder in terms of combustion?

  • Fine particles accelerate the rate of combustion. (correct)
  • Fine particles allow for more controlled explosions.
  • Fine particles decrease the velocity of combustion.
  • Fine particles lead to less powerful explosions.

What consideration must be taken into account when using fine-grained powder for black powder production?

  • It requires a more complex manufacturing process.
  • It is less effective than coarse powder.
  • It can lead to faster-burning characteristics and potential dangers. (correct)
  • It reduces the overall effectiveness of black powder.

What is the primary reason for analyzing particle size in powder formulations?

<p>To ensure proper dosing of the medication (D)</p> Signup and view all the answers

What does Stokes' law relate to in the context of particle size?

<p>The settling velocity of particles in a fluid (D)</p> Signup and view all the answers

How does particle size affect drug release and bioavailability?

<p>Smaller particles increase the surface area available for dissolution (C)</p> Signup and view all the answers

Which of the following is NOT a benefit of controlling particle size during formulation?

<p>Increased likelihood of segregation in mixtures (A)</p> Signup and view all the answers

What is a potential consequence of using coarse particles in lung delivery systems?

<p>They are likely to cause an irritant sensation (D)</p> Signup and view all the answers

What type of dispersion technique was employed in the particle size analysis of α-lactose monohydrate?

<p>Sonication in butan-1-ol (D)</p> Signup and view all the answers

Why are fine particles preferred in some formulations for suspensions?

<p>They minimize rapid settling in fluids (B)</p> Signup and view all the answers

What magnification was used to observe the photomicrograph of salbutamol sulphate micronised powder?

<p>x 5560 (D)</p> Signup and view all the answers

What is the relationship between particle size and the angle at which light is scattered according to laser light scattering principles?

<p>Larger particles scatter at smaller angles. (D)</p> Signup and view all the answers

What assumption is made about the particles in the laser light scattering method?

<p>Particles are spherical and opaque. (B)</p> Signup and view all the answers

In a particle size distribution, what is typically observed between fine and coarse particles?

<p>The number of fine particles exceeds the number of coarse particles. (D)</p> Signup and view all the answers

Which piece of equipment is essential for detecting scattered light in laser light scattering techniques?

<p>Photodetectors. (D)</p> Signup and view all the answers

What does a positive skew in particle size distribution indicate?

<p>More fine particles than coarse ones. (D)</p> Signup and view all the answers

What does the median size represent in a cumulative size distribution plot?

<p>The size below which 50% of the particles lie. (B)</p> Signup and view all the answers

What is indicated by 25% and 75% cumulative undersize values in particle size analysis?

<p>The upper and lower quartiles of the particle size distribution. (C)</p> Signup and view all the answers

Which characteristic is associated with the % cumulative undersize distribution for particles?

<p>Represents a visual distribution pattern of particle sizes. (D)</p> Signup and view all the answers

Which shape factor would be most relevant for assessing the sphericity of pellets?

<p>Circularity (B)</p> Signup and view all the answers

What is the lower limit of particle size that can be effectively measured using a Coulter counter?

<p>0.3 mm (B)</p> Signup and view all the answers

Which characteristic is important for analyzing powder packing?

<p>General geometric shape (B)</p> Signup and view all the answers

What is a common problem encountered when using a Coulter counter?

<p>Particles being too small for detection (A)</p> Signup and view all the answers

Which of the following methods is known for its high speed and versatility in measuring particle size?

<p>Laser light scattering (A)</p> Signup and view all the answers

Which qualitative description is NOT valid for particle shapes?

<p>Standardized (B)</p> Signup and view all the answers

What does the shape factor 'circularity' measure?

<p>How close a shape is to being circular (D)</p> Signup and view all the answers

What issue arises from using particles that are too large in the Coulter counter?

<p>They can block the orifice (B)</p> Signup and view all the answers

What is the concept of an equivalent sphere in particle measurement?

<p>A sphere equal to the real particle in the physical parameter being measured. (C)</p> Signup and view all the answers

Which diameter is defined as the distance between two tangents on opposite sides of a particle?

<p>Feret’s diameter. (A)</p> Signup and view all the answers

What does the British Pharmacopoeia provide concerning particle shape?

<p>Descriptive terms to classify the shape qualitatively. (C)</p> Signup and view all the answers

What is the requirement for geometric figures like spheres or cubes in relation to particle characterization?

<p>Need only one dimension for identification. (A)</p> Signup and view all the answers

Which of the following size fractions is α-lactose monohydrate mentioned as being mixed with ipratropium bromide?

<p>63-90 µm (D)</p> Signup and view all the answers

What is measured by the Martin’s diameter?

<p>The distance measured crosswise on a line bisecting the projected area. (C)</p> Signup and view all the answers

Which diameter corresponds to a circle with the same area as the particle profile?

<p>Equivalent circle diameter. (B)</p> Signup and view all the answers

What is the difference in accuracy concepts between particle size methods and other analytical methodologies?

<p>Particle size methods employ different criteria for measuring accuracy. (A)</p> Signup and view all the answers

What is considered the starting point in particle size measurement?

<p>Optical light microscopy (B)</p> Signup and view all the answers

Which factor does NOT need to be considered before measuring particle sizes?

<p>The molecular weight of the particles (C)</p> Signup and view all the answers

What is one of the mechanisms involved in liquid dispersion of particles?

<p>Shear stress via ultrasound waves (C)</p> Signup and view all the answers

What aspect does the sampling scheme primarily aim to avoid?

<p>Bias in sample selection (B)</p> Signup and view all the answers

How does dilution impact particle size distribution in liquid dispersion?

<p>It does not change the distribution if the dispersing fluid mimics the host fluid (D)</p> Signup and view all the answers

What key issue is highlighted when using measurement techniques for particle size that do not measure size directly?

<p>There is often a weak correlation with actual size (C)</p> Signup and view all the answers

Which of the following is NOT a physical property of the powder to consider before sampling?

<p>Molecular structure (A)</p> Signup and view all the answers

What is the role of randomization in the sampling process?

<p>To avoid bias in sample selection (D)</p> Signup and view all the answers

Flashcards

Particle Size

The size of individual particles within a substance.

Particle Shape

The shape of individual particles, like round, needle-like, or irregular.

Preformulation

The process of evaluating and optimizing the physical and chemical characteristics of a drug before it can be made into a medicine.

Combustion

The process of burning, involving a chemical reaction with oxygen, producing heat and light.

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Black Powder

Black powder is a mixture that burns quickly and creates a lot of pressure, used in weapons and fireworks.

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Particle Size Analysis

The process of determining the distribution of particle sizes in a powder or suspension.

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Powder Segregation

The tendency of particles of different sizes to separate during mixing, leading to uneven drug distribution.

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Powder Flow

How easily a powder flows, influenced by particle size, shape, and surface properties.

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Bioavailability

The ability of a drug to be absorbed into the bloodstream and exert its effect.

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Micronization

The process of reducing the size of solid particles to increase surface area and potentially improve drug dissolution.

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Particle Settling

The movement of suspended particles under gravity, influenced by particle size and density.

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Surface Area

The surface area of a drug available for dissolution and absorption, affected by particle size.

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Equivalent Sphere

A sphere that has the same value for a specific physical property as the real particle being measured.

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Feret's Diameter

The shortest line between two parallel tangents on opposite sides of the particle, measured perpendicularly to the tangent lines.

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Martin's Diameter

A line drawn through the center of the particle, perpendicular to the longest axis. The distance between the two points where it intersects the particle's outline.

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Equivalent Circle Diameter

The diameter of a circle that has the same area as the projected outline of the particle.

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Equivalent Volume Diameter

The diameter of a sphere with the same volume as the particle.

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Accuracy of Particle Size Methods

The methods used to determine the size of particles are different from other analytical methods. Therefore, the accuracy of particle size measurement has special considerations.

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Particle Size Grade

A particle size grade is a range of sizes that a particle can fall within.

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Sphericity

A measure that compares the actual surface area of a particle to that of a sphere with the same volume. High values indicate a more spherical shape.

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Circularity

A two-dimensional shape factor that quantifies how much a particle deviates from a perfect circle. Calculated by dividing the area of the particle by the area of a circle with the same perimeter. Higher values indicate more circular shapes.

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Image Analysis

A method for determining particle size using microscopic images. It measures the shape's area, perimeter, and diameter. This information can be used to calculate shape factors like sphericity and circularity.

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Coulter Counter

A method for measuring particle size using electrical conductivity. Particles are suspended in an electrolyte and passed through a small opening. The change in electrical conductivity is measured, which correlates to the particle's volume.

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Sieve Analysis

A dry screening method that separates particles based on size using a set of sieves with different mesh sizes. This method measures weight distribution by isolating particles within each size range.

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Laser Light Scattering

A method for particle size analysis using laser light scattering. The laser beam interacts with the particles and the scattering pattern is analyzed to determine size distribution.

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Qualitative Shape Description

A qualitative method for describing particle shape based on visual observation using a microscope. Common descriptions include acicular, angular, round, fibrous, flaky, and cubic.

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Quantitative Shape Determination

A quantitative method for measuring particle shape using various techniques, including shape factors like sphericity and circularity, as well as image analysis and microscopy.

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Purpose of Size Measurement

Before measuring particle size, consider how the data will be used. This involves factors like the intended application, statistical analysis needed, and if the measurement needs to control specific particle behavior.

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Formulation Type and Particle Size

The type of formulation (e.g., tablet, suspension) influences the particle size required. For example, a suspension needs smaller particles for uniform dispersion, while tablets may need larger particles for good flow.

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Particle Size Distribution

The range of particle sizes in a sample is called the size distribution. Particle size distribution directly influences the properties of your material. For example, a narrow distribution may be desired for a tablet, while a broader distribution may be needed for a suspension.

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Powder Properties

Before conducting a sampling scheme, we must consider the nature of the powder. This includes physical properties like packing, how well it flows, whether it breaks easily, and whether it tends to separate into different sizes.

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Sample Size

The amount of powder available directly affects the sample size. A larger sample size generally leads to a more accurate measurement.

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Sampling Bias

Ensure your sampling technique avoids bias. For example, don't just pick the easiest particles to scoop up - use a random approach to get a representative sample.

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Liquid Dispersion

A liquid dispersion technique is often used for particle size measurement. This involves dispersing the particles in a liquid that mimics the environment where the drug will be used.

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Number vs. Weight Distribution

A plot representing the number of particles within specific size ranges.

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Equivalent Area Diameter

In particle size analysis (e.g., using a microscope), it's the size of a particle represented as the diameter of a circle with the same area as the particle being measured.

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Cumulative Undersize Distribution

A graph showing the percentage of particles that are smaller than a certain size. This is a cumulative representation of particle size distribution. The mid-point of this distribution is the median size. 25% and 75% points represent the lower and upper quartiles, respectively.

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Sieving

A type of measurement that uses a sieve of defined mesh size to separate particles. This method is commonly used to determine the size of particles in a sample.

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Cumulative Oversize Distribution

The percentage of particles that are larger than a certain size. It's the complementary information to the cumulative undersize distribution.

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Median Size

The middle value in a sorted set of data. It represents the 50th percentile of the data and divides the distribution into two halves.

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Study Notes

MPharm Programme - Particle Size & Shape

  • This presentation covers preformulation aspects of particle size and shape.

  • Particle size in black powder significantly influences its burning characteristics. Fine powder burns faster but creates excessive pressure; thus, larger particles with consistent size are preferred.

  • A-lactose monohydrate, a powder, was studied using microscopy and laser light diffraction methods at different magnifications for various particle size ranges (e.g., 63-90 µm). Image analysis illustrated irregular, complex particle shapes.

  • Particle size analysis, including laser diffraction and sonication in butan-1-ol, was used to create distribution curves for different materials.

  • The importance of particle size is discussed, relating it to excipient choices in powder mixtures for consistency, flow characteristics, and uniformity of low-dose drugs. The influence of particle size on surface area and drug release/bioavailability is also highlighted.

  • Measurement techniques for particle size are detailed, including microscopy (optical light), sieve analysis, laser light scattering, conductivity measurements (using the Coulter Counter), and image analysis. Appropriate techniques depend on the specific material, accuracy needs, and available resources.

  • Equivalent spheres are used in particle size analysis. Various types of dimensions are calculated (e.g., Equivalent (projected) area, Equivalent volume, Equivalent surface diameters). The physical parameters used for comparisons are also emphasized.

  • Qualitative methods for describing particle shape like acicular, angular, round, fibrous, or flaky are described alongside quantitative methods such as aspect ratio and elongation. These factors are also applied to specific examples including (lactose, sodium carboxymethylcellulose, calcium carbonate, and sodium chloride).

  • The methodology for studying particle size distributions, like using log-probability paper and plots of number versus weight distributions, has been covered.

  • An example of using optical microscopy with an eyepiece graticule is shown to determine equivalent area diameter.

  • Particle size distribution is often described by showing a positive skew, with fine powders more prevalent than larger ones. Various examples illustrating these analysis methods are included.

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Particle Size & Shape PDF 2024-1

Description

This quiz focuses on the preformulation aspects of particle size and shape within the MPharm programme. It examines the impact of particle size on burning characteristics, excipient choices, and drug release properties. Various methods for particle size analysis, including microscopy and laser diffraction, are also covered.

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