What Is a Tablet Hardness Tester?
A tablet hardness tester is an instrument used to measure the hardness of pharmaceutical tablets and other similar products.
The hardness of a tablet is indicative of its physical properties. Generally, a harder tablet has lower solubility in the body. Conversely, a tablet with low hardness may break during transportation, affecting the stability, uniformity, and potentially the composition of the product. Therefore, controlling tablet hardness is essential.
Other tests, such as disintegration tests, confirm a tablet’s solubility in the body. It is often observed that tablets with low hardness disintegrate more easily. However, recently developed orally fast-disintegrating tablets can disintegrate quickly despite having low hardness.
Applications of Tablet Hardness Testers
Tablet hardness testers are primarily used in research and development, as well as in quality control of tablets, particularly in the pharmaceutical industry.
During the design and improvement stages of pharmaceutical products, various quality parameters are checked. Hardness testing is a critical control item during the validation of manufacturing processes on the production line.
Post design confirmation, manufacturing commences. Some manufacturers routinely test tablet hardness as part of quality control. Hardness tests are also conducted for quality assurance in response to complaints.
Principles of Tablet Hardness Testers
Tablet Hardness Testers measure the hardness of a tablet by placing it between two plates. Pressure is applied at a constant rate in one direction, and the force required to break the tablet is measured. This hardness value reflects the tablet’s breaking strength (the force needed to break the cross-section) and/or crushing strength (the force required to completely destroy the shape and structure).
Several factors influence measurement accuracy. The pressure plate clamping the tablet must have a smooth, frictionless contact surface and be parallel to the tablet. The load application rate during pressurization should be constant to avoid unpredictable crushing and sudden load application. Consistent tablet orientation during testing is also crucial for reproducible results. For instance, tablets with a scored line should be aligned either parallel or perpendicular to the pressure plate.
Various types of tablet hardness testers exist, differing in the structure of the tablet holding section and the mechanism of the pressure plate movement. Simple manual testers include the Monsanto type, which applies pressure using a spring and screw, the Pfizer type that utilizes pliers for pressure application, and the Strong Cobb type, which employs compressed air for loading.