Texture Analysis in Action: the Tablet Coating Adhesion Rig

The TABLET COATING ADHESION RIG (HDP/TCA) performs an important task in ensuring that changes to the composition of coatings do not adversely affect the efficacy of the medication.

Solid inclusions in the form of aluminium lakes of water-soluble dyes, opacifiers (for example, titanium dioxide), and various inorganic materials are often added to tablet film coatings to improve their appearance (for example, colour and opacity), barrier properties, and in some cases their film-forming characteristics.

Measurement of tablet coating
adhesive force

Defects such as cracking and edge splitting and peeling can be a consequence of change of materials and can have a profound effect on the release of an active ingredient, especially if the tablet has been coated with an enteroinsoluble or sustained-release film.

This test provides a quantitative measure of the adhesion strength of the coating to the tablet surface. Such a test is useful for studying the consequences of changes in tablet coating formulation variables.  

Some more information on this fixture:
The use of the Tablet Coating Adhesion Fixture allows a sample to be supported, in a cavity of definable dimensions, and held down whilst an Adhesive test is performed. The tablet coating is carefully removed from around the circumference of each tablet, using a scalpel. Both fixture cavities (upper and lower) are covered with double-sided adhesive foam tape. This tape is pushed firmly into each cavity (before removal of the exposed surface backing). The tape backing is removed and the prepared tablet is then positioned centrally in the lower cavity and the test is commenced.

During the test the upper fixture comes down onto the tablet with a specific force for a specific time, both of which are suitable to achieve good contact between the tablet surface and fixture cavity and sufficient to compress the tablet into both cavities to receive full coating contact with the foam tape. The upper fixture is then withdrawn at 10mm/s, either removing the upper coating or leaving the lower coating in the stationary fixture. The maximum force required to separate the tablet from its coating is taken as the ‘tablet coating adhesion force’. The graph above shows a typical curve of such a test. This test provides a quantitative measure of the adhesion strength of the coating to the tablet surface. Such a test is useful for studying the consequences of changes in tablet coating formulation variables.

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We can design and manufacture probes or fixtures for the TA.XTplus texture analyser that are bespoke to your sample and its specific measurement.

Once your measurement is performed, our expertise in its graphical interpretation is unparalleled. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can also prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.

For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

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