GPAT 360

Identification of Emulsion type. Basically, emulsions are of two types : o/w and w/o . Click here to view the article on What is an Emulsion? Following tests are conducted in order to identify the type of emulsion. 1. Cobalt chloride test: Filter paper soaked in cobalt chloride solution and dried , changes colour from blue to pink when exposed to the o/w (oil in water) emulsion. 2. Dilution test: This test is based on the miscibility of continuous phase in the oil or water. For example, if water is added with stirring in o/w emulsion , it will easily disperse in added phase (water) but w/o emulsion will not get dispersed. This method causes phase inversion of emulsions upon dilution. 3. Conductivity test: An emulsion with water as a continuous phase (o/w emulsion) passes the electric current , whereas the w/o emulsion is not able to do so. 4. Direction of creaming: When densities of the water and oil phases are known, direction of creaming test identifies emulsion type.  Creamin

  Emulsion Instead of a long definition, let's get to know this term in small divided forms. Emulsion is a thermodynamically unstable system. It consists of two immiscible liquids (one is generally water and another is oil)  It consists of one phase dispersed into another in the form of globules/ droplets. Either oil is dispersed in water (o/w) or water is dispersed into oil (w/o) This system is stabilized by adding suitable emulsifying agent(s). The liquid which is dispersed in the form of small globules is known as dispersed phase . The liquid in which globules are dispersed is known as continuous phase . For example - if paraffin oil is dispersed in the form of globules into water, paraffin oil is a dispersed phase and water is a continuous phase. This system is o/w i.e. oil in water emulsion. The dispersed phase is also known as discontinuous phase or internal phase. The continuous phase is also known as dispersion media or external phase. 1. While formulating an emu

1. Capsule number and their approximate capacity in mg and ml No.  : mg  : ml 000 : 950 : 1.37  00  : 650 : 0.95    0  : 450 : 0.68    1  : 300 : 0.50    2  : 250 : 0.37    3  : 200 : 0.30    4  : 150 : 0.21    5  : 100 : 0.13 ¶  Remember that  000 is the largest capsule size while 5 is the smallest size . 2. Sucrose based diluents 1. DiPac : 97% sucrose + 3% modified dextrose 2. Nutab : 95% sucrose + 4% invert sugar 3. Sugar tab : 90-93% sucrose + 7-10% invert sugar 3. Proportions (of respective oil) required for a primary emulsion                              ( Oil: water: gum) Fixed oils     --  4 : 2 : 1 Mineral oils --  3 : 2 : 1 Volatile oils --  2 : 2 : 1 Oleoresins   --  1 : 2 : 1 4. How to remember the names of Span and Tween surfactants? Tweens are known as Polysorbates or polyoxyethylene sorbitan fatty acids . Spans are known as Sorbitan esters. Generally used Tweens and Spans have grades such as 20, 4

1. What is Draves test? Draves test is used for measuring the efficacy of wetting agent. Procedure: In this test, 5 gm cotton skein is attached to a 3 gm hook, which is tied by means of a thread to a weight. The skein is placed into a cylinder containing the surfactant solution to be tested and is held submerged by the hook and the thread is attached to the weight.  As soon as most of the air is displaced by the liquid, the skein sinks to the bottom. The shorter the sinking time, the better the wetting agent. The gray cotton skein used for this purpose contains natural waxes and oil that make it hydrophobic and wetting is not instantaneous, hence the test measures the rate of wetting . 2. General terms of solubility phenomenon There are four general terms used to define solubility of system viz. Cosolvency, solubilization, complexation and hydrotrophy. a) Cosolvency : It is the phenomenon of increasing the solubility of weak electrolytes and non-polar molecules by addition o

Every year 1-2 questions are asked in the GPAT exams from these general topics of Pharmaceutics. 1. Terms of solubility Descriptive term Volume of solvent in ml per gm of solute Very soluble Less than 1 Freely soluble 1 to 10 Soluble 10 to 30 Sparingly soluble 30 to 100 Slightly soluble 100 to 1000 Very slightly soluble 1000 to 10,000 Practically insoluble More than 10,000 2. Flow characteristics of materials    PROPERTY CHARACTER TYPE OF LIQUID Newtonian Follows Newton’s law Liquids with simple molecules and solid dispersion. Non- newtonian         Dilatancy or shear thickening Shear dependent viscosity. Increase in apparent viscosity with increase in rate of shear. Suspensions with high solid content of small deflocculated particles.       Pseudoplasticity or shear thinning