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Tablet hardness testing

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Tablet hardness testing, is a process that tests for the breaking point and structural integrity of a tablet "under conditions of storage, transportation, and handling before usage" [1] The breaking point of a tablet is based on its shape. [2] It is similar to friability testing [1], but they are not the same thing.

History

Tablet hardness testers first appeared in the 1930's [3] In the 1950's, the Strong-Cobb tester was introduced. It was patented by Robert Albrecht on July 21, 1953.,[4] It used an air pump. The tablet breaking force was based on arbitrary units referred to as Strong-Cobbs. [3] The new one gave readings that were inconsistent to those given by the older testers.[3]

Later, electro-mechanical testing machines were introduced. They often include things like motor drives, and the ability to send measurements "to a computer". [3]

Process

There are 2 main processes to test tablet hardness: compression testing and 3 point bend testing.

Compression testing

The user generally aligns the tablet in a repeatable way. [2] It is squeezed by 2 jaws The first machines continually applied force with a spring and screw thread until the tablet started to break. [3] When the tablet fractured, the hardness was read with a sliding scale.[3]

Machines

There are several devices to perform this task.

Monsanto tester

It was developed 50 years ago. The design consists of "a barrel containing a compressible spring held between 2 plungers". The tablet is placed on the lower plunger, and the upper plunger is lowered onto it. [5] [1]

Strong-Cobb tester

A plunger forces an anvil against a stationary platform. Results are viewed from a hydraulic gauge. [5] The results are very similar to that of the Monsanto tester. [6]

Pfizer tester

Compresses tablet between a holding anvil and a piston connected to a force-reading gauge when its plier-like handles are gripped. [5]

Erweka tester

The tablet is placed on the lower anvil and a weight moving along a rail transmits pressure slowly to the tablet.[5]

Schleuniger tester

The main difference is that this one operates in a horizontal position. An electric motor drives an anvil to compress a tablet at a constant rate. The tablet is pushed against a stationary anvil until it fractures. A reading is taken from a scale indicator. [5]

Sources

  1. ^ a b c http://books.google.ca/books?id=NFGSSSbaWjwC&pg=PA916&lpg=PA916&dq=tablet+hardness+testing&source=bl&ots=V70VQffsvp&sig=oLTB79KfO5Y2yLH01BBfNL0U-mw&hl=en&sa=X&ei=3d7cUOTrBMXP2QXTkYGgDg&ved=0CEwQ6AEwAzgU#v=onepage&q=tablet%20hardness%20testing&f=false
  2. ^ a b http://www.sotax.com/Hardness.116.0.html
  3. ^ a b c d e f http://www.engsys.co.uk/pages/testing.php
  4. ^ http://www.google.com/patents?id=kq9MAAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q&f=false
  5. ^ a b c d e http://www.scribd.com/doc/6766629/QCtablet
  6. ^ http://onlinelibrary.wiley.com/doi/10.1002/jps.3030440208/abstract;jsessionid=5A4D91011A70C0579B16826E0FA8BCD2.d04t04
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