DETERMINATION OF EMULSION TYPES
There are many methods available for the determination of emulsion type but the most commonly used are: Drop dilution method. Dye solubility method. Fluorescent test. Electrical conductivity test. Direction of creaming test. Filter paper test. These methods determine whether the emulsion is oil in water (o/w) type or water in oil (w/o) type.
DROP DILUTION METHOD: This method is based on the principle that emulsion is always miscible with the external phase. If water is added to water in oil w/o type emulsion, it will not be mixed. On the other hand, oil mixes well. Same is the case with o/w type emulsion. If oil oi l is added to oil in water o/w type emulsion, it will not be mixed. On the other hand, water mixes well.
DYE SOLUBILITY METHOD: It is based on the solubility of any dye in the external phase. Amaranth, a water soluble dye gives color to oil in water o/w type emulsion, but not to water in oil w/o type emulsion. Same is the case with oil soluble dyes.
FLUORESCENT TEST: Based on the fluorescence of oils under ultraviolet light, the emulsion is examined under the light in the microscope. If the whole fluid is fluorescent, it is water in oil w/o but in case of oil in water o/w spotty fluorescence will appear.
ELECTRICAL CONDUCTIVITY TEST: Based on the electrical conductivity of aqueous solutions, the electric current is supplied and electrodes are placed in the emulsion. If the current is passed, it is oil in water o/w and if is not passed, it is water in oil w/o.
DIRECTION OF CREAMING TEST: Creaming is the sedimentation of the dispersed phase which is either upwards or downwards, upon which this test is based. The density of oil is mostly less than water. Thus if creaming is at the upper side, it is oil in water o/w and if it is downwards, it is water in oil w/o type of emulsion.
FILTER PAPER TEST: Take a filter paper, put a drop of emulsion on the filter paper. Evaporate it; if there is a spot on the filter paper, the emulsion will be water in oil w/o. On the other hand, if there is no spot, the emulsion will be of oil in water o/w type.
DETERMINATION OF TOTAL SOLIDS
The term “total solids” is applied to the residue obtained when the prescribed amount of the preparations is dried to constant weight under the conditions specified. Total solids usually include extractives, both soluble and insoluble in alcoholic or hydroalcoholic preparations as tinctures and extracts. The total solids are calculated as g/100ml This test is more preferably performed for the tinctures or galenical preparations containing a higher amount of solid contents.
PROCEDURE: Take a china dish, weigh it then add 5ml of the tincture or the given preparations. Heat this to evaporation. Then weigh it again. Increase in weight is the weight of total solids in 5ml of sample. Specific ranges are given in pharmacopoeia.
EVALUATION OF ELIXIRS
Elixirs are clear sweetened usually hydro-alcoholic liquids containing flavoring substance.
TESTS FOR THE EVALUATION OF ELIXIR Following are the tests for the evaluation of elixirs. Consistency. pH determination. Refractive index Alcoholic contents. Identification. Assay of active contents.
CONSISTENCY: Should be clear.
pH DETERMINATION: 6.0 to 7.0.
REFRACTIVE INDEX: 1.4608-1.4630.
ALCOHOL CONTENTS: It should be
1 of the percentage given in the monograph.
IDENTIFICATION: To 5ml add 2ml of 5M NaOH and mix. A liquid with the odour of chloroform is separated.
ASSAY OF ACTIVE CONTENTS: To 3 grams add 25 grams of Zinc powder, 15ml of glacial acetic acid. Add 30ml of water, boil under reflux condenser for 30 minutes, cool, filter through absorbent cotton, wash the residue with water and combine the filtrate. Add 20 ml of 2M Nitric acid, wash the residue with water and titrate the excess of silver nitrate with 0.1M Ammonium Thiocyanate using Ammonium iron sulphate as an indicator. Each ml of 0.1M silver Nitrate 0.005513 grams of C2H3Cl3O2.
EVALUATION OF SYRUPS
Syrups are concentrated aqueous solutions having 66.7 % w/v of sucrose. Syrups also contain aromatic or other flavoring materials.
TESTS FOR EVALUATION OF SYRUPS Following tests are specified for the evaluation of syrups: Consistency. pH determination. Refractive index. Identification of active contents. Assay of active contents. Solubility.
CONSISTENCY: Should be clear solution. There should be no solid particles.
pH DETERMINATION: Determine the pH of syrup by suitable means; it should be 6.0 to 7.0.
REFRACTIVE INDEX: The value of refractive index should be in the range of 1.4608 to 1.4630.
IDENTIFICATION OF ACTIVE CONTENTS: Identify the active contents of syrup by suitable means e.g. invert syrups dissolve with 10 ml of water and 5ml of potassium cupric tartarate solution. A red precipitate is produced.
ASSAY OF ACTIVE CONTENTS: For example, Lemon syrup.
Mix 8 grams with 100ml of water and titrate with 0.1M NaOH using phenolphthalein as an indicator. Each ml of 0.1M NaOH=0.007005 grams of C6H8O7.H2O
SOLUBILITY: Soluble in water.
EVALUATION OF SUPPOSITORIES
Suppositories are semisolid preparations administered through the orifices, each contain one or more medicaments. They are normally administered as a single dose for local or systemic action.
TESTS FOR THE EVALUATION OF SUPPOSITORIES Appropriate test methods and specifications are developed, which are capable of guaranteeing that the purpose for which suppositories are used will be fulfilled.
TESTS FOR SUPPOSITORIES ARE: 1. 2. 3. 4. 5. 6.
Uniformity of weight Disintegration test. Content uniformity test. Melting point determination test. General appearance test. Assay of active contents.
1). UNIFORMITY OF WEIGHT: Weigh 20 suppositories individually. Determine their average weight. Not more than two of individual weights should deviate from the average weight more than 5% and none deviates by more than 10%.
2). DISINTEGRATION TEST: APPARATUS: A transparent sleeve of glass or suitable plastic of height 60mm with an internal diameter of 52mm. A metal device consisting of two stainless discs each of which contain 39 holes, each 4mm in diameter. Diameter of the disc is closely similar to the internal diameter of the sleeve. Discs are separated by a distance of 30mm. Metal device is attached to outer sleeve by means of three equally spaced hooks. Method: Place a suppository on the lower perforated disc of metal device and then insert the device into the cylinder and attach this to the sleeve. Repeat the same operation with further two suppositories, metal device and sleeve. Place each piece of apparatus in a vessel containing at least five liters of water at 37C and fitted with a slow stirrer and by means of holding the top of apparatus 90 mm below the surface of water. After every 10 minutes invert each apparatus without removing it from water. Disintegration is complete when molded suppositories are: Completely dissolved. Dispersed into its components. Have become soft. Disintegration occurs in not more than 30 minutes for fat based suppositories and for water-soluble suppositories disintegration occurs in not more than 60 minutes.
3). CONTENT UNIFORMITY TEST: Take 10 suppositories; determine the active ingredients of each of the 10 suppositories by using a suitable analytical method. If not more than one of the individual values thus obtained is outside the limit i.e. % of the average value and none of them is outside the limit i.e. 25% of the average value. Repeat the test by using another 20 suppositories taken at random. If out of 30 suppositories not more than 3 individual values are outside the limit 15% of the average values and none is outside the limit 25% of the average value, then the test is O.K, otherwise failed.
4). MELTING POINT DETERMINATION TEST: Melt the suppositories rapidly at a temperature not more than 10C above the point of complete fusion. Insert one end of glass capillary tube into the melted substance so that a column of substance become 8-12 high rise into it. Cool the tube to 15C and maintain the temperature at 15-17C for not less than 16 hours. Attached the tube to thermometer in the heating vessel containing water at 15C so that the lower end of the column of substance is 30mm below the surface of water. Heat the water with constant stirring, so that the temperature rise at a rate of 2C per minute. The temperature at which partially melted substance begins to rise in the tube is regarded as the melting point. The melting point of suppositories should not rise more than that given in the monograph.
5). GENERAL APPERANCE: When cut longitudinally, the internal and external surface should be same.
6). ASSAY OF ACTIVE CONTENTS: Official limit for the active contents is 95- 105% e.g. Glycerol Suppositories. Dissolve a number of suppositories equivalent to 8 grams of glycerol in 50 ml of water and add quantity sufficient to produce 250ml. Take 5ml of this solution and 150ml of water and 0.25ml of Bromocresol purple solution and add 0.1M.NaOH to neutralize the blue color of indicator. Add 1.6 grams of sodium metaphenolate and allow to stand for 15 minutes and titrate with 0.1M NaOH to same blue color. Each ml of 0.1M NaOH=0.00921 grams of glycerol.
EVALUATION OF OINTMENTS
Ointments are semisolid preparations applied to skin with or without friction.
SPECIFIED TESTS FOR EVALUATION OF OINTMENTS The evaluation of a drug means to perform the tests for the maintenance of quality and quantity according to the specifications. After the manufacturing of drug or during the production, the specific tests are done for that particular product to evaluate it. Following tests are specified for the evaluation of ointments: Weight variation test. Consistency. Identification of active contents. Assay of active contents. Melting point. Solubility.
1). WEIGHT VARIATION TEST (USP) Select the sample of 10 filled container and remove any labeling that might alter weight during removing of the contents from the containers. Thoroughly clean and dry the outside of the container by a suitable means and weigh individually. Remove the contents from each container by cutting opening and washing with a suitable solvent, taking care to retain the closures and any other parts of each container. Dry and again weigh each empty container together with its corresponding parts. The difference between weights is the net weight of the contents of each container. The average net weight of contents of 10 containers is not less than the labeled amount and the net weight of contents of any single container is not less than 90% of the labeled amount, where the labeled amount is more than 60 grams but not more than 150 grams. If the requirements are not met, determine the net weight of the contents of 20 additional containers. The average weight of the contents of 30 containers is not less than the labeled amount and the net weight of contents of not more than one container of the 30 containers is not less than 90% of the labeled amount, where the labeled amount is 60 grams or less and not less than 95% of the labeled amount, where the labeled amount is more than 60 grams but not more than 150 grams.
2). CONSISTENCY Should be smooth, no solid particles.
3). IDENTIFICATION OF ACTIVE CONTENTS Warm a saturated solution in water with Silver Ammonium Nitrate solution in a test tube. Metallic Silver is deposited as a mirror on the sides of the tube.
4). ASSAY OF THE ACTIVE CONTENTS For example: Salicylate ointment. Dissolve 10 grams in a mixture of 20 ml of alcohol (95%) previous neutralized to phenol red solution and 20ml of ether and titrate with 0.1N NaOH using phenol red solution as indicator. 1ml of 0.1N NaOH=0.01381 grams of salicylic acid.
5). MELTING POINT Not less than 11C.
6). SOLUBILITY Should be soluble in 9 parts of water and 17 parts of boiling water, miscible with alcohol, with solvent such as ether, chloroform or with volatile oils.
DETERMINATION OF ALCOHOLIC CONTENTS OF VARIOUS GALENICAL PREPRATIONS
In most of the galenical preparations, alcohol is used. There are two methods for the determination of alcoholic contents. DISTILLATION METHOD. GAS LIQUID CHROMATOGRAPHY.
DISTILLATION METHOD This is the general method used for the determination of alcohol, unless specified in the individual monograph. This method is suitable for examining most fluid extracts and tinctures, provided the capacity of distillation flask is sufficient (commonly 2-4 times the volume of the liquid to be distilled) and the rate of distillation is such that clear distillates are produced. Cloud y distillates may be clarified by agitation with TALC or with white ppt of CaCO3 and filtered after which the temperature of the filtrate is adjusted and the alcoh ol contents are determined from the specific gravity given is B.P.
PRECAUTIONS: During all procedure minimize the loss of alcoho l by evaporation. Bumping may be prevented during distillation by making the solution alkaline with milk of magnesia or by adding porous chips of insoluble material glass or capillary tubes each sealed off at one end. Frothing: treat the liquids that froth to a troublesome extent during distillation by rendering them strongly acidic with phosphoric sulfuric or tannic acid or treat them with a slightly excess of CaCl2 solution or with a small amount of paraffin or silicone oil before starting the distillation.
(A). FOR LIQUIDS PERSUMED TO CONTAIN LESS THAN 30% OF ALCOHOL: Take 25ml of the sample in the distillation flask. Add some amount of distilled water mixed and distilled it. Take the distillate 2ml less than the original sample. Bring the temperature at which the procedure was started. Add sufficient amount of distilled water to the distillate to make volume 25ml. Calculate the specific gravity and note the percentage of alcohol from the table given in B.P.
(B). FOR LIQUIDS PERSUMED TO CONTAIN MORE THAN 30% OF ALCOHOL: Take 25ml of the sample in the distillation flask. Add twice the volume of distilled water. Mix and distill it. Take the distillate 2ml less than the double amount of sample. Bring the temperature at which the procedure was started Add sufficient amount of distilled water to make the volume 50ml. Calculate the specific gravity and note the percentage of alcohol from the table given in B.P.
SPECIAL TREATMENT: VOLATILE ACIDS AND BASES: The preparations that are basic in nature are treated with dilute H2SO4 before distillation and the preparations that are acidic in nature are treated with NaOH solution before distillation. GLYCERIN: To the liquids containing glycerin, add sufficient amount of water so that residue after distillation contain 50% of water. IODINE: All the solutions containing free Iodine should be treated with Zinc before the distillation or decolorize with Nathiosulphate followed by a few drops of NaOH. OTHER VOLATILE SUBSTANCES: When spirits elixirs, tinctures and similar preparations contain volatile materials other than alcohol such as volatile oils, chloroform, ether, camphor, they require special treatment as follows:
(A). FOR LIQUIDS PRESUMED TO CONTAIN LESS THAN 50% OF ALCOHOL: For example: SPIRIT CHLOROFORM Take 25ml in a separating flask. Add to it 50ml of brine solution, i.e. saturated solution of NaCl. Add 40ml of petroleum ether or petrol and shake for 2 minutes then take the lower layer. Add again 50ml of brine solution to the separating flask and take the lower layer i.e. aqueous layer. Distill whole of the aqueous solution containing brine solution. The distillate equal to the volume of original sample is collected. Calculated the specific gravity and noted its percentage from the table given in B.P.
(B). FOR LIQUIDS PRESUMED TO CONTAIN MORE THAN 50% OF ALCOHOL: Adjust the sample up to 25% alcohol by diluting it with water then proceed as given in the procedure above.
EXAMPLE: ALCOHOLIC CONTENTS IN EXTRACT GLYCYRRHIZA: To 25ml sample add 40ml of N/10 H2SO4 into distillation flask. Add 70ml of water. Collect the distillate about 70ml. Add water to it and make the volume to 100ml. Calculate the specific gravity and note its percentage from the table given in B.P.
GAS LIQUID CHROMATOGRAPHY (GLC): APPARATUS: The instrument contains a column of 2mm by 4mm packed with polyethylene glycol. The column is maintained at 100C. The injection part is equipped with a solid filter and is maintained at 160C. An inert gas such as gallium is used as carrier at a flow rate of about 60ml per minute. STANDARD SOLUTIONS: For liquids containing more than 10% alcohol, prepare two standard solutions, one with 5 % less and one with 5% greater concentration than the expected concentration of the sample. Standardize them by calculating its specific gravity and noting the percentage from the table given in B.P.
For liquids containing less than 10% alcohol, prepare two standard solutions one with 1% less and one with 1% greater concentration than the expected concentration of the sample. Standardize them by calculating specific gravity and noting the percentage from the table given in B.P. PROCEDURE: Treat the sample and each of the standard solution as followed: Take 25ml in a container with stopper. Add 10ml of internal standard (Acetone) for each 6ml of alcohol. Mix and add water if necessary. Inject appropriate quantity into the apparatus. From the chromatogram obtained, we can calculate the percentage of alcohol as by using the following formula: [S1 (Y-Z)+S2 (Z-X)] (Y-X) Where: S1: %age of alcohol in standard solution 1. S2: %age of alcohol in standard solution 2. X, Y and Z are the ratio of alcohol peak area to the internal standard peak areas for the standard solution 1, standard solution 2 and the sample respectively.
