Particle Size and Shape

Optical light microscopy is the initial technique for starting particle size measurement. It involves magnifying a sample using a microscope and visually assessing the size of particles.

The color of particles does not influence the accuracy of particle size measurement. The measurement techniques are based on physical properties rather than visual properties.

Materials with low occupational exposure limits (OEL) must be adequately contained during particle size measurement to prevent worker exposure to hazardous substances.

Surface tension reduction is a mechanism involved in the liquid dispersion of particles. It helps to break down forces holding particles together and promote their separation.

Techniques that do not directly measure particle size often measure particle volume. This is because particle volume is closely related to size.

In a sampling scheme, randomization of samples is crucial to avoid bias in particle selection. This ensures representative data.

The water solubility of a powder can affect its particle behavior before size measurement. Solubility can lead to clumping or dissolution, influencing the measurement.

The physical properties of the powder are a primary characteristic to consider when preparing a particle size measurement. These properties influence method selection and accuracy.

The primary reason for assessing particle size during formulation is to select appropriate excipients and ensure uniformity. This affects product performance and bioavailability.

The flow rate of powders is inversely proportional to particle size. Smaller particles flow more slowly due to increased friction between them.

For lung delivery applications, very fine particles are preferable. They can reach the deeper parts of the lungs, increasing drug delivery efficiency.

Particle size influences the available surface area, affecting release rates. Smaller particles have a larger surface area, leading to faster drug release.

Laser light diffraction after dispersion in butan-1-ol is the method used for particle size analysis in the content provided. This technique utilizes the scattering of laser light by particles to determine their size.

It's critical to control particle size during manufacturing to influence processing operations and product performance. Particle size can affect flow, compaction, and other critical stages.

The magnification level of the photomicrograph of salbutamol sulphate micronised powder in the content provided is x 5560. This means the image is magnified 5560 times compared to the actual size.

Fine particles in suspensions reduce the likelihood of a 'scratchy' feeling on the skin. This is because they are smoother and distribute more evenly.

An equivalent sphere in particle measurement is a sphere that matches the particle in the property being measured. It's used to simplify calculations for non-spherical particles.

Feret's diameter is used to measure the distance between two tangents on opposite sides of a particle. It represents a specific linear dimension of the particle.

For spheres, cubes, and regular tetrahedrons, particle size methods only require one dimension. This is because they have predictable shapes and sizes.

The equivalent volume diameter represents the diameter of a sphere with a volume equal to that of the particle. It's a way to relate size and volume.

The British Pharmacopoeia uses descriptive terms to characterize the shape of particles. These terms like 'spherical', 'acicular', 'and 'irregular' classify the overall shape of a particle.

For non-spherical particles, particle size and shape are characterized through multiple dimensions and identification of shape. These dimensions are used to create a comprehensive profile of the particle.

The shape of powder particles is a fundamental property that directly influences their behavior. It affects packing, flow, and surface area.

The main effect of particle size on the combustion of black powder is that fine-grained powder burns faster than larger particles. This is due to increased surface area for the reaction.

Historically, black powder was made with larger particles to slow down the rate of burn and prevent explosions. Larger particles burn more slowly, providing controlled combustion.

Fine powdered black powder had a larger surface area for combustion, making it more powerful. With more surface exposed, the reaction happens faster.

A disadvantage of using fine-grained black powder was that it built up too much pressure too quickly. This could lead to uncontrolled explosions.

The combustion of black powder mainly occurs on the surfaces of the particles. This is because the reaction requires contact with oxygen.

Sphericity is a property that characterizes roundness in particle shape. It's often used to describe the deviation of a particle from a perfect sphere.

Qualitative description of shape alone does not contribute to the quantitative characterization of particle shape. This requires measurements and analysis for a more precise understanding.

The Coulter counter detects changes in electrical conductivity as particles pass through an orifice. This change allows it to count and size particles.

A limitation of the Coulter counter method is that particles can clump together and give inaccurate readings. This is because the method relies on individual particle passage.

When studying powder packing, the general geometric shape of the particles should be primarily assessed. This shape influences how the particles fit together.

Laser light scattering offers high speed and high reproducibility for particle size analysis. It's a widely used technique for its efficiency.

Angular particle shape characterization is typically assessed using the projected area ratio. This ratio compares the projected area of the particle to its actual area.

Sieve analysis for particle size measurement can be influenced by the moisture content of the particles. This is because moisture can cause particles to clump or stick together.

In laser light scattering, larger particles scatter light at a smaller angle. This is because they deflect the light less, resulting in a smaller scattering angle.

When calculating scattering in laser light scattering, the assumption is made that particles are spherical and opaque to light. This assumption is used to simplify calculations.

A positive skew is typically observed in the number of fine particles compared to coarser particles. This means the distribution is shifted towards smaller sizes.

In particle size distribution analysis, a 50% cumulative undersize represents the median size of the particles. It's the point where half the particles are smaller and half are larger.

The values representing the lower and upper quartile in a particle size distribution plot indicate 25% and 75% of the total number of particles. These values help to define the spread of the distribution.

Cumulative undersize distribution is NOT used in the optical microscopy example for determining particle size. This method relies on direct observation and measurement.

A positive skew in the particle size distribution suggests that the distribution is centered around smaller particle sizes. This means there are more smaller particles in the sample.

The data processing unit in laser light scattering analyzes and interprets the scattering data. It converts the raw data into meaningful particle size information.

Particle size influences how powders behave, how they're processed, and how effective a drug is.

Visual techniques like light microscopy are the first step to understand particle size. They give a general idea.

Materials with low OELs (occupational exposure limits) need extra safety precautions during measurement to protect workers.

The way a powder packs, flows, breaks easily, and how much is available all influence how you measure particle size.

To deliver drugs to the lungs, smaller particles are better because they can reach deeper parts of the lung.

Particle size influences the flow of powders, with smaller particles tending to flow slower.

Measures how much a particle's shape deviates from a perfect sphere.

A technique that measures the change in electrical conductivity as particles pass through an orifice.

A statistical measure that indicates the distribution of particles is skewed towards smaller sizes.

Determines the size of particles based on how they scatter light.

A quantitative method to describe particle shape, by comparing the projected area to the actual area.

A method for determining particle size using a series of sieves with progressively smaller openings.

The process of breaking down a powder into small particles, enabling dispersed particles to be observed for size measurement.

A method used to visually assess the particle size using a grid pattern in the eyepiece lens of a microscope.

The distance between opposite sides of a particle measured across its widest point, bisecting its projected area.

The diameter of a circle with the same area as the particle's outline when projected onto a plane.

The particle's shape is a fundamental property that influences its behavior, such as how it packs, flows, and interacts with other materials.

It's a widely used method for particle size analysis. The method involves shining a laser beam onto a dispersed sample and measuring how the light is scattered by the particles.

This method involves using a series of sieves with decreasing mesh size to separate particles based on their size. It's a simple and widely used method.

It's a common technique for particle size measurement, especially for powders. The method involves passing a suspension of particles through a small opening and measuring the change in electrical conductivity.

These terms are used to classify the shape of particles based on their overall appearance, for example, 'spherical', 'acicular', 'irregular'.

The accuracy in particle size methods refers to how close the measured size is to the true size distribution of the particles in the sample, unlike other analytical methods where accuracy often relates to reproducing the same result.

The weight distribution of particles across a series of sieves, with different mesh sizes, is used to determine the size distribution of a powder. Smaller particles pass through finer sieves, while larger particles are retained on the coarser sieves.

The arrangement of sieves in a stack, with progressively coarser meshes towards the top, ensures that particles are separated based on their size during sieve analysis.

A method used to prevent particles from clumping together during particle size analysis. Surfactants, pH adjustment, and ultrasound waves are used to disperse particles in a liquid medium.

The ability of a surfactant to lower the surface tension of a liquid allows the liquid to penetrate between particles, separating them and promoting better dispersion in particle size analysis.

By adjusting the pH of the liquid medium, the surface charge on particles can be changed, influencing the attractive or repulsive forces between them. This can help prevent aggregation and improve particle dispersion.

Ultrasonic waves create high pressure differences in a liquid medium, which can efficiently separate very small particles, like those in the micron or sub-micron range.

The zeta potential, a measure of the electrical charge on a particle's surface, is influenced by pH. By adjusting the pH, the zeta potential can be manipulated to maximize repulsion between particles, preventing aggregation and promoting dispersion.