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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