Image Analysis
Image analysis is a powerful analytical technique which can provide additional information on a sample compared to standard particle size and distribution. The majority of particle sizing techniques assume an equivalent spherical diameter determined from measuring a related physical property (projected area, scattered/blocked light, displaced volume, etc.). This simplification is advantageous as a sphere is the only shape which can be described using a single number (i.e diameter). This assumption is acceptable in many applications where a comparison between samples is needed. In real world applications, particles are seldom spherical and cannot truly be described with a single number. The additional parameters provided by image analysis can help provide further insight into important properties which can affect dissolution, flowability, processing differences and material handling issues of a sample.
Image analysis involves digitally capturing images of a sample using a CCD camera. The digital image is composed of pixels and each pixel is assigned a grayscale value. Thresholding is then performed within the image analysis software package, which assigns a value whereby each pixel is designated as particle or as background (non-particle). Once thresholding has been performed and the system calibrated using NIST traceable standards, measurement of the digital image is performed. Upon completion of the measurement, results are available on a variety of size, shape, and intensity parameters, such as Circular Area Diameter, Length/Width, Aspect Ratio, Circularity, Convexity, and Opacity/Transparency along with several others depending on the instrument manufacturer. The numerous parameters and output formats available in modern image analysis software can provide exciting new ways for PTL to evaluate a client’s sample.
Using static imaging, the particulate is dispersed onto a stage where it remains fixed during analysis. Static imaging systems offer versatility in that various sample states can be analyzed: dry powders, liquid suspensions, particulate captured on filters, in addition to creams and lotions. These systems also have the ability to reanalyze the same particles more than once, allowing for more in-depth investigation.
PTL has used image analysis since our company’s inception to solve client problems and provide innovative solutions to their projects. PTL’s years of experience with image analysis and stringent quality system allow our clients to have the highest confidence in the results provided. Contact us to discuss how image analysis may be a valuable tool to evaluate your samples.
Advantages
- Robust technique capable of analyzing samples prepared wet, dry, in creams, or on filters
- Provides number weighted particle size distribution
- Additional reportable parameters: circle equivalent diameter, aspect ratio, length, width, circularity, etc.
- Allows for the analysis of heterogenous materials
Considerations
- Automated approach can lend to long analysis times
- Helpful as an orthogonal technique to more conventional particle sizing methods
- Heterogenous material cannot be distinguished
Sample Requirements
Sample amount is not an easy question to answer, since it depends on the particle size and general nature of the material. Ideal sample amount is 1 gram for solid samples. For liquid samples the preferred amount is 20 mL.
Although, less sample can be analyzed if need be. Questions on sample needs – please contact us to share specifics about your sample and options for suitable sample quantities.
Detection Range
Typically, PTL’s Microscopy Department can measure particulate from approximately 0.5 micrometers (um) up to 1000 micrometers (um). Actual range of detection range may differ based on the objective yielding smaller and larger ranges.
Data Reported
Image Analysis reports provide a number weighted particle size distribution on a variety of parameters including diameter, aspect ratio, and circularity. Additional parameters can be reported upon request such as length, width, convexity, and etc. Please reach out to learn more about the various reporting options.
Sample Reports
Instrumentation
Particle Technology Labs uses the Malvern Morphologi 4-ID for our image analysis testing.
