The presence of agglomerates of particles of a compound can affect the compound’s properties, for example, its flowability in a process or its bioavailability in a pharmaceutical final product.
In many industries monitoring the size of the particles alone is not sufficient to detect agglomerates especially if large primary particles are also present. This is because measuring size alone cannot distinguish between large particles or agglomerates.
Image Analysis using Morphologi G2
Analysis using the Morphologi G2 image analysis instrument provides qualitative data in terms of images of every single particle in the sample. This complements the quantitative data, for example, the size distribution of the sample that the instrument also provides. In addition the Morphologi G2 measures particle shape in terms of a variety of morphological factors. The particles can then be classified in terms of size and/or one or more shape parameters. Therefore, primary particles, agglomerates of particles or different types of particles found in the sample can be clearly identified and the proportion of each type can be determined.
Example Four samples of glass beads with a polydisperse size distribution were dispersed onto a Morphologi G2 glass plate by manual sprinkling resulting in varying amount of agglomerates. Analysis using the Morphologi G2 was performed using a Standard Operating Procedure (SOP). This specified the measurement requirements in a single electronic file and included classification of the particles in order to identify the level of agglomerates in each sample.
The particles were classified as shown in table 1.
Table 1. Classification set up in SOP to identify different types of particles.
Circularity > 0.96
Circularity ≥ 0.896 < 0.96
Circularity < 0.896
Convexity < 0.873
Examples of the types of particles identified in each of the classes are shown in figure 1.
Figure 1. Examples of a) Primary spheres b) Primary misshapen particles c) Agglomerates.
The proportion of each type of particle within a sample can be displayed in a table (figure 2) or a bar chart and overlaying the results of several samples allows them to be compared (figure 3).
Figure 2. Table showing the numbers of particles counted for each type of particle.
Figure 3. Bar chart comparing the proportions of the different types of particles in various samples.
The Morphologi G2 software provides classification functionality which allows the proportion of different types of particles or the degree of agglomeration in a sample to be easily detected and quantified.