INTRODUCTION:

The word cosmetics arises from the Greek word ‘Kosmeticos’ which means adorn. Drugs and Cosmetic Act 1940, defined cosmetics as ‘any article intended to be rubbed, poured, sprinkled, sprayed on or applied to the human body or any other part thereof for cleaning, beautifying, promoting attractiveness or altering the appearance.’^[1] The various cosmetic preparations include powders, creams, sunscreen preparations, shampoos, hair colourants, dentifrices, lipsticks, nail polish, Mascaras.

Powders:

1. Shade control and lightening:

The first is comparison of the appearance of the body of the powder to a standard when it is spread out and flattened on a white paper background. The second manner of evaluating colour is comparison of the sample to the standard by skin tone (under tone).

2. Dispersion of colour:

The uniformity of a powder can be easily be checked by spreading it on white paper and examining it with magnifying glass. If any non-uniformity is detected, further processing to achieve maximum colour development should result in homogeneity.

3. Pressure testing:

In a compressed powder, the pressure applied must be of a uniform nature, since the pressure of air pockets will result in a cake which will easily broken. Uniformity and hardness of a cake are checked by means of penetrometer.

4 Breakage test:

The most successful manner of checking the tendency of a pressed powder table to break or chip is to drop assembled compact on a wooden surface several times from the height of 8-10 inches if the cake remains unbroken, it is an indication that the compact can travel and will undergo normal handling without unsatisfactory results.

5. Pay-off test:

Pay off means adhesion characteristic with powder puff, of a compact or pressed powder should be tested on the skin. High pay off due to application of low pressure in formulation, hence soft cake formed that tends to crumble and break easily and more powder adhere on puff. Low pay off means high pressure and formation of hard cake so hard that will not rub off the cake enough to adhesion the material to the puff easily.

6. Particle size:

It was determined by stage microscopic method, sieve analysis or by counter coulter technique.

7. Moisture content:

It can be estimated with Karl fisher apparatus, IR moisture balance and other calorimetric analysis method.

8. Abrasiveness:

It is determined by rubbing the powder on a smooth surface and then studying the effect on surface using microscope.

9 Flow properties of powder:

It can be studied by measuring angle of repose of powder. It is important for the body powders as they should come out easily from the container for easy application.^[2]

Creams:

1. Rheology:

Rheological measurements are utilised to characterize the ease of pouring from a bottle, squeezing from a tube or container.

2. Sensitivity:

This test is normally done by patch test on skin and can be either open or occlusive. The test sample is applied along with a standard market product at different places and effect is compared after a period of time.

3. Effect of thermal stresses:

Here creams are evaluated by subjecting them to too high and low temperatures in alternating cycles. The samples are first exposed to 60⁰ for a few hours and then to 0 to 40⁰. Such exposures are repeated a number of times and emulsion stability assessed after each cycle.

4. Phase separation:

The rate and degree of phase separation in an emulsion can be easily determined by keeping a certain amount in graduated cylinder and measuring the volume of separated phase after definite time intervals. The phase separation may result from creaming or coalescence of globules. The phase separation test can be accelerated by centrifugation at low or moderate temperatures.^[3]

Sunscreen preparations:

1. Spectrophotometric evaluation:

This is basically to evaluate the UV radiation absorption ability of the sunscreen compounds. Using a UV spectrophotometer and taking specific concentration of a substance on the preparation, molar extinction coefficient or absorbency can be determined and compared with any other standard substance.

2. Erythemal dosage:

It is important to estimate the erythemal effective radiation or E-vitons/cm2, transmitted by a suntan preparation. The erythemal energy is the product of the solar energy transmitted through the film of suntan preparation and the effectiveness factor at that wavelength.

3. Sunscreen index:

This is evaluation of the relative screening activity of the sunscreen compounds. This is measurement of extinction coefficient at 308mu wavelength and comparison withother 308mu in the peak wavelength for effective sunburn.

4. In vivo skin testing:

This is a direct test on animal skin, particularly rabbit. Preparations are applied on a specific site (backside or abdomen) and exposed to radiation along with a control unprotected site, for a specific period of time. The effects are observed at the end of period. Test influencing variables include radiation source, size of test field etc.,^[4]

Shampoos:

1. Foam ability:

Foaming is essential for consumer acceptance although it is not a measure of cleaning action. With the help of Rose-milles foam column method, foam height and foam stability is measured.

2. Cleansing properties:

Also known as detergency action. Since shampoos are used for the cleansing purpose so it is real measure of property of shampoo. It is done on wool yarn and grease method. Place 5g of wool-yarn covered in grease and put it in 200ml of water containing 1g of shampoo in a flask. Shake the flask for 4minutes at 50 revolutions per minute. Remove the shampoo from solution, dry itand weigh. Now calculate the amount of grease and dirt, remove under experimental conditions.

3. Sensitivity:

On humans sensitivity testing of cosmetics may be performed either as diagnostic or as prophylactic test. By diagnostic test it is intended to discover whether the cosmetic used has caused dermatitis, if cosmetic is known the ingredient which has caused it. It is known as diagnostic patch, prophetic test is done to assess whether a new cosmetic should be placed in market or not.

4. Colour:

Shampoo colour selection has evolved to the increasing use of light, bright, eye-catching shades. Introduction of improved colour stabilising systems and merchandising techniques that have made product and package mutually supporting. Any colouring of shampoos must be done with certified colours.

5. Consistency:

Thick products may be advantageous in reducing spoilage or loss during application but may be difficult to disperse through the hair. Thinner products may hold an advantage where rapid dispersion and cleaning are desirable and where loss due to inadvertent handling is unlikely.

6. Package:

Shampoos should be contained in packages of good barrier properties, passage of water vapour; essential oil and air through the container possess a threat to product stability.

7. Eye irritation test:

This is also a type of consumer acceptance test, consumer prefer only those shampoos which are less irritant and cause no stinging sensation in eyes.^{[1] [3] [4]}

Hair colourants:

1. Consistency:

It should not be too viscous, otherwise application will be difficult. The consistency should be Minimum so that after application it will not drain off.

2. Spreadability:

Hair dye should be easily spreadable so that it can easily apply evenly.

3. Colour uniformity:

The colour of the hair dye and hair colour should be uniform; colour shade should be retain same, and must give desired colour after application.

4. PH:

PH must be neutral.

5. Allergy test:

Draize modified scoring technique was used to evaluate the skin irritation at 24hrs for seven days. Skin irritation studies were performed on healthy rabbits. The dorsal surface (50cm²) of the rabbits was cleared and the hair was removed by shaving. The skin was cleansed with rectified spirit. Natural dye was applied over the skin. The skin was observed for skin irritation, oedema formation for six days. Or the allergy test can be performed by the following procedure. Behind the ear using a cotton bud, apply a small quantity of unmixed colourant product sufficient to cover an area of 1-2cm². Reapply two to three times allowing it to dry between each application. Leave it for 48 hours. During this period, any abnormal reactions such as itching, redness or swelling in or around the test area must not occur.^[1]

Hair removers:

1. Estimation of hair removing agent:

As high concentration of the hair remover may be dangerous, it is necessary to measure the quantity. It must be done by instrumental chemical analysis.

2. Toxicity test:

This test can be done on animals. For this purpose, rabbit can be used. Preparations can be applied for hair removaland the effect on the skin can be studied by observation or by microscopic study.

3. Stability:

Stability of the product is very important. This is done by any normal stability study or accelerated stability study at high temperature.

4. Rheology:

It can be studied by using suitable viscometer.^[4]

Dentifrices:

1. Abrasiveness:

Various tests have been designed and reported over the year, mostly on the set of extracted teeth. The teeth were mechanically brushed with paste (or) powder and then the effects were studied by observation, mechanical (or) other means. Abrasive character normally depended on the particle size. So, study of particle size can also give such idea.

2. Particle size:

This can be determined by microscopic study of particles (or) by sieving (or) other means.

3. Cleansing property:

This is studied by measuring the change in the reflectance character of lacquer coating on a polyester film caused by brushing with a tooth cleanser (paste (or) powder). Also, an in vivo test has been suggested in which teeth were brushed for 2weeks and condition of teeth were assessed before and after use with the help of photographs.

4. Consistency:

It is important that the product, paste should maintain the consistency to enable the product press out from the container. Study of viscosity is essential for this. Rheology of powder is also important for proper flow of power on the container.^{[1] [4]}

5. PH of the product:

5gm of all samples was accurately weighed and placed in a 150ml beaker. To this 45ml of freshly boiled and cooled water was added at 27⁰c. It was stirred well to make a thorough suspension. The ph was determined for all samples within five minutes by using pH meter.

6. Foaming character:

This test is specially required for foaming tooth paste (or) powders. About 5gm of each sample was weighed and placed in a 100ml glass beaker. To this 10ml of water was added and the glass beaker was covered with a watch glass and allowed to stand for 30 minutes, this operation was carried to disperse the toothpaste in water. The contents of the beaker were stirred with a glass rod and the slurry was transferd to a 250ml graduated measuring cylinder, during this transfer ensure that no foam was produced and no lump paste went into the measuring cylinder. The residue left in the beaker was transferred with further portion of 5-6ml of water to the cylinder. The content of cylinder was adjusted to 50ml by adding sufficient water and the content has to be maintained at 30⁰c. Stir the contents of the cylinder with the glass rod to ensure a uniform suspension. As soon as the temperature of the content reached 30⁰c, the cylinder was stoppered and the complete shakes were given to it. The cylinder was allowed to stand for five minutes and the volume of the foam with water and water only was noted for all samples. The foaming power can be determined by, Foaming power=V1-V2 V1- Volume in ml of foam with water V2- Volume in ml of water only.

7. Limit test for arsenic and lead:

This is very important as these are highly toxic metals. Specific tests are there to estimate these two metals. However, if the raw materials are tested for the limit of these two metals, products may not have excess of such metals.

8. Determination of volatile matter and moisture content:

Aspecified amount of the product is taken and is kept for drying till a constant weight is obtained. The weight of the product before and after drying is measured. Loss of weight will be indicating % of moisture and volatile matter.

9. Effect of special ingredients:

The use of therapeutic ingredients may lead to certain incompatibilities and hence specific tests are done in order to determine the effect of such ingredients such as antiseptics, enzymes, etc.,

10. Determination of fineness:

10gm of each sample was accurately weighed and placed in a 100ml beaker. To this 50ml of water was added and allowed to stand for 30min with occasional stirring until the toothpaste was completely dispersed. This solution was passed through 150-micron Indian Standard Sieve. Then the sieve was washed with running tap water. Washing should be continued until all the matters passed by through the sieve. After washing the residue remains on the sieves were collected and dried in an oven at 105⁰c. Calculation: For all the samples fineness was calculated by using the formulae: Percentage by mass =100M₁/M M₁-Mass in grams of residue retained on sieve. M- Mass in grams of material taken for test.^[5]

Lipsticks:

1. Melting point determination:

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 60-65⁰c in order to avoid sensation of friction or dryness during application. The method of determination is known as capillary tube method. In this method, about 50mg of lipstick is taken and is inserted into a glass capillary tube open at both ends. The capillary tube is ice cooled for about hours and then placed in beaker containing hot water and magnetic stirrer. The temperature at which material starts moving through the capillary is said to be the melting point temperature. Another important parameter is the droop point which determines the temperature at which the product starts oozing out the oil and becomes flattened out. The melting point should be higher than the droop point which determines the safe handling and storage of finished product.

2. Breaking point:

This test is done to determine the strength of the lipstick. The lipstick is held horizontally in a socket ½ inch above the base and weight is applied on the lipstick, ½ inch away from the edge of the support. The weight is gradually increased by a specific value at a specific interval of 30 seconds and weight at which the lipstick breaks is considered as breaking point. This test should be done at specific temperature (say 25⁰c) and lipstick should be stored at temperature for at least 30minutes prior to the test.

3. Thixotropy character/Test for penetrability:

This test indicates the rheological property of lipstick with the help of penetrometer. A needle of specific diameter is allowed to penetrate the lipstick and depth of penetration is needed.

4. Test for force of application:

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 of application. Or Lipstick is applied on the piece of paper (kept on a balance) at an angle of 45⁰ and the force required for applying is read from the balance.

5. Aging stability:

The product is stored at 40degee centigrade and periodical observation of oil bleed, crystallization of wax on surface and application character is made.

6. Perfume stability:

This is also done by storing at 40⁰c and periodically comparing, after bringing the temperature down, with a fresh lipstick.

7. Oxidative stability:

This is predicted by standard determination of peroxide value after exposure to oxygen under given conditions.

8. Surface anomalies:

This is studied by the surface defects, such as formation of crystals on surface, contamination by moulds, fungi etc. formation of wrinkles, exudation of liquid substances of solid fatty substances.

9. Accelerated stability test:

This test aging can be studied at higher temperature (45⁰c) or alternatively keeping at 45⁰c and 0⁰c and observing the changes.

10. Determination of colour dispersion:

The test is done is done in order to determine the uniform dispersion of colour particle. The size of the particle is determined by the microscopic studies and it should not be more than 50 microns.^[6]

Nail polish:

1. Non-volatile content:

This can be done by taking a definite amount of lacquers and apply on a plate of flat surface. Weight of the residual film after evaporation of solvent will indicate the non-volatile content.^[7]

2. Drying rate:

This can be done by taking the product on a flat surface and touching the product with tip of finger at short intervals of time to feel the tackiness. Time taken foe disappearance of tackiness is noted.^[8]

3. Smoothness:

This is the character of the film. This film is applied on the surface characteristics of the film are studied microscopically. Before applying a nail lacquer, moisture and traces amount of soil should be removed from the surface of the nail to ensure good adhesion and loss.^[1]

4. Hardness:

This is the measure of the hardness of the film. It can be determined by Sward Rocker and Tukon microhardness tester. Film of 0.0006 inch should be cast on a glass plate and dried for 48hrs at 25⁰c and an additional 2hrs at 71⁰c. The film is evaluated with Rocker. The rocker consists of two 4-inch metal rings spaced 1 inch apart and a gravity bob for regulating the oscillation frequency. In order to make hardness test, the rocker is placed on the levelled surface and set in motion. The total time required for the amplitude of oscillation to decay by a fixed amount corresponding to certain number of complete oscillations is a measure of hardness of the test panel. A range between 8-10 oscillations is normal. The Tukon microhardness tester consists of a load applicator and indenter and a microscope fitted with a movable stage. The coating of film is applied to a rigid surface. After the film is dried for a given period, a load is placed on the surface of coating for approximately 18sec through a pyramid shaped diamond. The resultant permanent impression made by the diamond is measured with a filar micrometer and the length of the identification is converted to a Knoop Hardness Number (KHN). This number relates the applied load in grams to the unrecovered projected area in square millimetres. KHN increases in magnitude with increasing film hardness.^[8]

5. Adhesion:

This is the measure of adhesion character of the film with adhesion surface. This is done by applying the film over a glass plate (using a Bird Type Film Applicator with fixed cut) forming a layer of uniform thickness. A TA XT2i Texture analyser from stable microsystems was used to quantify the adhesive characteristics. The glass plate was clamped down and the force applied was measured against time and distance. A TA-57 (7mm-1R) probe was used in this study. The probe was lowered from a height of 10mm with 0.5-1.0 g of force until it reached the product surface. When it detected the surface, a trigger force of 40g was applied for 1sec. The probe was then withdrawn from the film, and the force required to pull the probe away was recorded and plotted against time. The maximum amount of force required to remove the probe from the sample was reported as the adhesive strength of the formulation. The AUC indicated the adhesive work. Finally, the distance of peak force was reported as stringiness. These parameters are useful in comparing the formulation variables and their effect on adhesion.^[9]

6. Abrasion resistant:

The Taber Abraser can be used to measure abrasion resistance through the action of two resilient abrading wheels which are made to rub the coated surface. The nail enamel coating is applied to four inch square steel panel having a centre spindle hold. The panel is placed on a turntable operating at a constant speed. Two abrading wheels, each ¾ inch wide are fixed on each side of spindle and in contact with the coating surface. A load upto 1000g may be placed on the wheels in addition to their own 250g weight. The direction of the abrasion pattern developed by one wheel is from the outside. A tachometer is provided to count the number of turntable rotations. Between the wheels, vaccum device acts to remove loose particle abraded from the coating. The instrument is operated for a specific number of cycles or until a portion of substrate is exposed. Result may be reported either as the number of cycles to failure per mil of film thickness or as the weight loss in milligrams per 1000 cycles.^[8]

7. Water resistance:

This is the measurement of the resistance towards water permeability of the film. A 0.0006-inch film on three glass plates should be applied and dried and then weigh these. The plates should then be immersed in a water bath containing distilled water at 37⁰c for 24 hours. The panels should then be removed and dried by placing the plate between absorption papers and reweighed. The increase in weight is calculated. Higher the increase in weight, lowers the water resistance.^[1]

8. Viscosity:

This is also an important character and can be measured by Brookfield viscometer. For Brookfield viscometer the sample should be taken in a closed jar to minimize the solvent evaporation. Sample should be aged atleast 8hrs at 25⁰c before performing the test. At 25⁰c, shake vigorously, start timer, insert spindle into the sample to the scored line, with the motor running at 60rpm. Spindle should be correct position in less than one minute. Read the instrument at the end of ten minutes then switch the speed control to 6rpm and read the instrument again at the end of another ten minutes. In order to convert the dail reading to centipoises, multiply by following factor-60rpm*20; 6rpm*200. The viscosity-thixotropy relationship of cream nail enamel should be about 375-500cps at 60rpm, at 250c.^[8]

9. Colour:

Colour comparing with mater colour standards by applying on thumbnails, holding them side by side, moving the thumb with the standard first on the right and then on left. Artificial acrylic nails have been utilized as well for matching comparative shades.^[10]

10. Stability:

Stability study of nail lacquers is very important and essential which can be performed by accelerated stability test. ^[11]

Mascaras:

1. Drop test:

This test is used for eye liner pencils to check the hardness and hardness and consistency of leads. Specially designed wooden slots are used to hold the uncased leads which are placed in an oven for 2 hours at 40degree c. The degree of bend or droop is measured and according to that grade is assigned.

2. Opening and closing patch test:

If eye cosmetic are the sources of the dermatitis, the distinction between irritant and allergic contact dermatitis must be made irritant contact dermatitis is more common than allergic contact dermatitis. Open or close the patch testing can be performed as with eye shadows.

3. Use testing:

Use testing is performed by placing the eye shadows at the corner of the eye for 5 consecutive nights followed by evaluation of the skin for irritant contact dermatitis.^[4]

REFERENCES:

1. Handbook of Cosmetics- B.M. Mithal, R.N. Saha.

2. Textbook of cosmetic formulations, Authors-Gaurav Kumar Sharma, Jayesh Gadiya, Meenakshi Dhanawak. May 2018.

3. Text Book of Cosmetics, Rajesh Kumar Nema, Kamal Singh Rthore, Bal Krishna Dubay.

4. Cosmetics- Formulation, Manufacture, Quality Control, 4^th Edition, P. Sharma.

5. Bureau of Indian Standards for tooth paste.IS 6356-1993.

6. Verma S., Tripathi D., Tiwari R. K. Formulation and Evaluation of Natural Lipsticks Prepared from Bixa Orellana Seeds and Daucus Carota Root Extract and their Comparitive study J Pharm Sci Bioscientific Res. 2017. 7(1):131-135.

7. Hand book of herbal products cosmetics, toiletries and perfume. Volume 1, National Institute of Industrial Research, Delhi, page no 255-256.

8. L. Mitchell, Schlossman. Technique for evaluation of nail enamel. Journal of Society of Cosmetic Chemists, 1980, 32,43-52.

9. V. Nalamothu, F. Verkh, L. Dragwa, w. Chern. Physical evaluation of medical nail lacquers using a text analyser. The AAPS Journal, 2002, 4(S1).

10. R.K. Khar, A. Nanda. S. Nanda. Cosmetic technology, 1^st edition 2007, Birla Publications Regd, Delhi, Page no. 12, 22.

11. Indian Standard of Nail of Polish (Nail enamel) specification (IS 9542:1994). Bureau of Indian standard, 2003.

Received on 03.11.2020 Modified on 11.12.2020

Res. J. Pharma. Dosage Forms and Tech.2021;13(1):76-81.

DOI: 10.5958/0975-4377.2021.00014.8