Friday 18 November 2016

Organoleptic properties & hardness of tablets
Color distribution must be uniform with no mottling. For visual color comparison compare the color of sample against standard color.
Hardness :
Tablet requires a certain amount of strength or hardness and resistance to friability to withstand mechanical shocks of handling in manufacture, packaging and shipping. Hardness generally measures the tablet crushing strength.
Hardness (crushing strength):
It is the load required to crush the tablet when placed on its edge.To determine the need for pressure adjustments on the tableting machine.  Hardness can affect the disintegration. So if the tablet is too hard, it may not disintegrate in the required period of time.  And if the tablet is too soft, it will not withstand the handling during subsequent processing such as coating or packaging.  In general, if the tablet hardness is too high, we first check its disintegration before rejecting the batch.  If the disintegration is within limit, we accept the batch. If Hardness is high + disintegration is within a time accept the batch.

Pfizer type hardness tester

                                     Monsento type hardness tester

Factors Affecting the Hardness:
a)     Compression of the tablet and compressive force.
b)     Amount of binder. (More binder à more hardness)
c)      Method of granulation in preparing the tablet (wet method gives more hardness than direct method, Slugging method gives the best hardness).
Limits: 5 kilograms minimum and 8 kilograms maximum.
 Make hardness test on 5 tablets and then take the average hardness.

Friability:
Friability of a tablet can determine in laboratory by Roche friabilator. This consist of a plastic chamber that revolves at 25 rpm, dropping the tablets through a Distance of six inches in the friabilator, which is then operate for 100 revolutions. The tablets are reweighed. Compress tablet that lose less than 0.5 to 1.0 % of the Tablet weigh are consider acceptable.

It is the tendency of tablets to powder, chip, or fragment and this can affect the elegance appearance, consumer acceptance of the tablet, and also add to tablet’s weight variation or content uniformity problems.

Friability is a property that is related to the hardness of the tablet. An instrument called Rouch friabilator is used to evaluate the ability of the tablet to withstand abrasion in packaging, handling, and shipping.
Procedure:
1. Weigh 20 tablets together = W1
2. Put these tablets in the friabilator and adjust the instrument at 100 rpm (i.e. = 25 rpm for 4 min)
3. Weigh the 20 tablets (only the intact ones) = W2
Friability (% loss) = W1 - W2/100
 It must be less than or equal to1 % but if more we do not reject the tablets as this test is non-official .Perform this test using 20 tablets that were used first in the weight variation test.

Thickness test

Thickness is an unofficial test. Thickness of the tablet is inversely proportional to hardness i.e. increase in hardness decrease the  thickness & vice versa. Thickness of tablet is measured by Vernier caliper/screw gauge. It is determined for 10 tablets.

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