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Tablet hardness testing

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Tablet hardness testing, is a laboratory technique used by the pharmaceutical industry to test 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.

Tablet hardness testers first appeared in the 1930s.[3] In the 1950s, the Strong-Cobb tester was introduced. It was patented by Robert Albrecht on July 21, 1953.[4] and 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 mechanisms like motor drives, and the ability to send measurements to a computer or printer.[3]

There are 2 main processes to test tablet hardness: compression testing and 3 point bend testing. For compression testing, the analyst generally aligns the tablet in a repeatable way,[2] and the tablet 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]

List of common hardness testers

There are several devices used to perform this task:

  • The Monsanto tester 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.[1][5]
  • The Strong-Cobb tester 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]
  • The 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 tests a tablet placed on the lower anvil and a weight moving along a rail transmits pressure slowly to the tablet.[5]
  • The Dr.Schleuniger Pharmatron tester 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]
  • The Kraemer Elektronik tablet testing system was the first automatic tablet hardness testing system for auto-regulation at tablet presses. Invented by the german mechanical engineer Mr. Norbert Kraemer in Darmstadt/Germany. The tablets are separated by a feeder chute and moved on a horizontal starwheel through different testing stations. The Kraemer Elektronik automatic tablet testing systems measure weight, thickness, diameter/length, width and hardness of tablets and capsules.Cite error: A <ref> tag is missing the closing </ref> (see the help page). Although the Strong-Cobb unit is arbitrarily based on the dial reading of a hardness tester, it became an international standard for tablet hardness in the 1950s until it was superseded by testers using SI units in the 1980s.[6] The Strong-Cobb is a unit with a very unusual name for a unit of measurement since it is named after the company, Strong-Cobb Inc. The inventor of the hardness tester was Robert Albrecht,[4] the plant engineer for the Strong-Cobb Company. He sold the patent to the company for $1.00.

Sources

  1. ^ a b c Joseph Price Remington (2006). Remington: The Science And Practice Of Pharmacy. Lippincott Williams & Wilkins. ISBN 0781746736.
  2. ^ a b "Tablet hardness testing". Sotax. Retrieved 16 February 2013.
  3. ^ a b c d e f "Some Information on Tablet Hardness Testing". Engineering Systems. Retrieved 16 February 2013.
  4. ^ a b Robert Albrecht (Jul 21, 1953). "Tablet Hardness Testing Machine". United States Patent Office. Retrieved 16 February 2013. US 2645936 
  5. ^ a b c d e "Quality control of solid dosage form". Scribd. Retrieved 16 February 2013.
  6. ^ a b McCallum, A., Buchter, J. and Albrecht, R. (1955). "Comparison and correlation of the Strong Cobb and the Monsanto tablet hardness testers". Journal of the American Pharmaceutical Association. 44 (2): 83–85. doi:10.1002/jps.3030440208. PMID 14353719.{{cite journal}}: CS1 maint: multiple names: authors list (link)

8. Automatic tablet hardness testing. Charles Ischi. Testing of oral solid dosage forms in R&D, quality control and in-process control.

Further reading

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