The evaluation studies are important in order to determine the efficiency, stability and the consistency of the finished product. The evaluation tests for the lipsticks are as follows:
EVALUATION
OF LIPSTICKS
The evaluation studies are important
in order to determine the efficiency, stability and the consistency of the
finished product. The evaluation tests for the lipsticks are as follows:
1.
Melting Point Determination Test:
The
determination of melting point is done in order to determine the storage characteristics of the product. The inciting
point of lipstick base should be between 60 to 65°C in order to avoid the
sensati on of friction or dryness during application. The method of
determination is known as capillary tube method:
(a)
In
this method, about 50 mg of lipstick is taken and is inserted into a glass
capillary tube open at both ends.
(b)
The
capillary tube is ice cooled for about hrs and then placed in a beaker
containing hot water and a magnetic stirrer.
(c)
The
temperature at which material starts moving through the capillary is said to be
the melting point temperature.
(d)
Another
important parameter is the droop point which determines the temperature at
which the product starts oozing out the oil and becomes flattened out.
(e)
The
melting point should be higher than the droop point which determines the safe
handling and storage of finished product.
2.
Breaking Load Point Test:
This
test is done in order to determine the strength and hardness of the lipstick. In this method, the lipstick is placed
hori7ental position I inch from the base and weights with increasing loads are
attached to it. the weight at which the lipstick starts breaking, known as the
breaking load point. The test shall be carried out in specific condition and at
about 25 ° C temperatures.
3.
Determination Of Thixotropic
Character:
This
is a test for determining the uniformity in
viscosity of base. The instrument used for the determination of thixotropic
character is known as the penetrometer.
4.
Microbiological Tests:
The
test is carried out in order to determine the extent of contamination either from the raw materials or mould. The test
involves the plating of known mass of sample on two different culture media for
the growth of microorganism and incubating them for a specific period of time.
The extent of contamination can be estimated by counting the number of
colonies.
5.
Test For Rancidity:
The
oxidation of oil such as castor oil and many other ingredients may result in bad odour and taste and also
result in a sticky product. The test for rancidity can be done by using
hydrogen peroxide and determining its peroxide number.
6.
Test for the Application Force:
This
is a test to determine the force to be applied during application. In this method, two lipsticks are cut to obtain flat
surfaces which are placed one above other. A smooth paper is placed between them
which is attached to a dynamometer to determine force required to pull the
paper indicates the force application.
7.
Storage Stability:
This test is done in order to
determine the stability of product during
storage.
8.
Stability to Oxidation:
The oxidation characteristics of the
finished product are determined in
order to check the stability of the product to oxidation. The extent of
oxidation can be determined by peroxide number of product after exposure or
substance to oxygen for a specific period of time.
9.
Determination of Surface
Characteristics:
The
study of surface property of the product is
carried out in order to check the formation crystal on the surface or the
contamination by microorganism or formation of wrinkles and the exudation of
liquid.
10.
Determination Of Colour Dispersion:
The test is done in order to
determine the uniform dispersion of
color particle. The size of the particle is determined by the microscopic
studies and it should not be more than 50µ.
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