QUALITY CONTROL TESTS FOR TABLETS

There are various quality control tests for tablets.Following is brief explanation of some important quality control tests for tablet.

TABLET HARDNESS:

The test measures crushing strength property defined as the compressional force applied diametrically to a tablet which just fractures it. Among a large number of measuring devices, the most favored ones are Monsanto tester, Pfizer tester, and Strong cobb hardness tester. All are manually used. So, strain rate depends on the operator. Heberlein Schleuniger, Erweka, Casburt hardness testers are motor driven.

FRIABILITY TEST:

The tablet may well be subjected to a tumbling motion. For example, Coating, packaging, transport, which are not severe enough to break the tablet, but may abrade the small particle from tablet surface. To examine this, tablets are subjected to a uniform tumbling motion for specified time and weight loss is measured. Roche friabilator is most frequently used for this purpose.

Tablet Diameter:

Tablet diameter is also an ipmortant test. We use pFizer tester for checking the diameter of the tablet,screw guage and calliper are also used. Tablet thickness can be measured by micrometer or by other device. Tablet thickness should be controlled within a ± 5% variation of standard value.

Tablet thickness:

Tablet thickness is an important qc test for tablet packaging.Very thick tablet affects packaging either in blister or plastic container.Tablet thickness is determine by the dia of the tablet.Pfizer tester is used for checkaging tablet thickness.

Weight Variation:

Take 20 tablet and weighed individually. Calculate average weight and compare the individual tablet weight to the average. The tablet pass the U.S.P. test if no more that 2 tablets are outside the percentage limit and if no tablet differs by more than 2 times the percentage limit.

Content Uniformity Test:
Randomly select 30 tablets. 10 of these assayed individually. The Tablet pass the test if 9 of the 10 tablets must contain not less than 85% and not more than 115% of the labeled drug content and the 10th tablet may not contain less than 75% and more than 125% of the labeled content.
If these conditions are not met, remaining 20 tablet assayed individually and none may fall out side of the 85 to 115% range.

Disintegration Test :
The breakage of tablet into smaller fragments is called disintegration of tablet.

The U.S.P. device to test disintegration uses 6 glass tubes that are 3” long; open at the top and 10 mesh screen at the bottom end. To test for disintegration time, one tablet is placed in each tube and the basket rack is positioned in a 1-L beaker of water, simulated gastric fluid or simulated intestinal fluid at 37 ± 20 C such that the tablet remain 2.5 cm below the surface of liquid on their upward movement and not closer than 2.5 cm from the bottom of the beaker in their downward movement. Move the basket containing the tablets up and down through a distance of 5-6 cm at a 

frequency of 28 to 32 cycles per minute. Floating of the tablets can be prevented by placing perforated plastic discs on each tablet.
According to the test the tablet must disintegrate and all particles must pass through the 10 mesh screen in the time specified. If any residue remains, it must have a soft mass.
Disintegration time: Uncoated tablet: 5-30 minutes
Coated tablet: 1-2 hours

Dissolution test:

The release of drug from the tablet into solution per unit time under standardize condition is called dissolution test.

Apparatus-1 (Basket Type): A single tablet is placed in a small wire mesh basket attached to the bottom

of the shaft connected to a variable speed motor. The basket is immersed in a dissolution medium (as specified in monograph) contained in a 1000 ml flask. The flask is cylindrical with a hemispherical bottom. The flask is maintained at 37±0.50C by a constant temperature bath. The motor is adjusted to turn at the specified speed and sample of the fluid are withdrawn at intervals to determine the amount of drug in solutions.