Lab Report: Emulsion
Evaluation of the Effects of Certain Content on the Characteristics of an Emulsion Formulation
Date of Experiment: 11th March 2013
Lecturer’s Name: Dr.Ng Shiow Fern
Aims:
- To identify the effects of HLB surfactant on the stability of the emulsion.
- To determine the physical and stability effects on the emulsion formulation due to the different of emulsifying agents used.
Introduction:
Emulsion is a thermodynamically unstable two phase system. It contain at least two immiscible liquids which one of them is dispersed homogenously (dispersed phase) in another liquid (continuous phase). Emulsion can be classified as two types: water in oil emulsion and oil in water emulsion. Emulsion can be stabilised by adding the emulsifying agent. Emulsifying agent can be divided into four type namely hydrophilic colloid, finely divided particles, surface active agent or surfactant.
HLB method is being used to identify the quantity and types of surfactant that is needed in order to produce a stable emulsion. Each surfactants, is numbered based on the HLB scale which is 1 (lipophilic) to 20 (hydrophilic). Usually, the combination of two emulsifying agents is used to produce a more stable preparation of emulsion.
Apparatus:
8 test tubes, 50mL measuring cylinder, 2 sets of pasture pipette and droppers, Vortex mixer, weighing boat, mortar and pestle, light microscope, microscope’s slides, 5mL pipette and a bulb, 50mL beaker, 15mL centrifuge tube, Coulter Counter, centrifuge machine, viscometer, 45°C water bath, 4°C fridge.
Materials:
Palm oil, Arachis oil, Olive oil, Mineral oil, distilled water, Span 20, Tween 80, Sudan III solution (0.5%) and ISOTON III solution.
Procedures:
1. Each test tube was labelled and a straight line was drawn 1cm from the bottom of the test tube.
2. 4mL of the given oil for each group and 4mL of distilled water were mixed in the test tube.
|
Group |
Test Oil |
|
1, 5 |
Palm Oil |
|
2, 6 |
Arachis Oil |
|
3, 7 |
Olive Oil |
|
4, 8 |
Mineral Oil |
3.Span 20 and Tween 80 were dropped into the mixture. The test tube was sealed and left to the Vortex mixture for 45 seconds. The time taken needed to reach the interface of 1cm was recorded. The HLB value of each samples were determined.
| No. of tubes |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| Span 20 (drops) |
15 |
12 |
12 |
6 |
6 |
3 |
0 |
0 |
| Tween 80 (drops) |
3 |
6 |
9 |
9 |
15 |
18 |
15 |
0 |
| HLB value | ||||||||
| Time of interface (min.) | ||||||||
| Stability |
4. A few drops of Sudan III solution were added to 1g of emulsion that was formed on a weighing boat and flattened. The colour dispersion in the sample was determined and compared under the light microscope. The shape and size of the globules formed were drawn, explained and compared.
5. 50g (of the given oil) Emulsion was prepared by using the wet gum method and the following formula.
| Arachis Oil |
25mL |
| Acacia |
6.25g |
| Syrup |
5mL |
| Vanillin |
2g |
| Alcohol |
3mL |
| Distilled water (qs) |
50mL |
6. 40g of the formed emulsion was added into a 50mL beaker and homogenization process was formed for 2 minutes by using a homogenizer.
7. 2g of the formed emulsion (before and after the homogenization) was put on the weighing boat and labelled. A few drops of Sudan III solution was added and flattened. The texture, consistency, degree of the oily shape and colour dispersion of the sample was determined and compared under the light microscope.
8. The formed emulsion viscosity (15g in the 50mL beaker) after the homogenization was determined by using the viscometer that has been calibrated with spindle type LV-4. The sample then was exposed to the temperature of 45°C (water bath) for 30 minutes and then to the temperature of 4°C (fridge) for 30 minutes. The viscosity of the emulsion was determined after the exposure and reached the room temperature for about 10-15 minutes.
| Readings |
Viscosity (cp) |
Average + SD |
||
|
1 |
2 |
3 |
||
| Before the exposure |
419.9 |
419.9 |
389.9 |
409.90±199.51 |
| After the exposure |
857.9 |
842.9 |
731.9 |
775.37±66.63 |
| Difference (%) |
89.16% |
|||
9. 5g of the homogenized emulsion was added into a centrifuge and was centrifuged (4500 rpm, 10 minutes, 25°C). The height of the interface formed was measured and the ratio was determined.
|
Interface |
Heights (mm) |
|
Separate phase |
20 |
|
Original emulsion |
39 |
|
Height ratio |
39/20 |
Results and Discussion:
1. What are the HLB values that form a stable emulsion? Discuss.
Palm Oil
|
Tube no. |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
|
|
Span 20 (drops) |
15 |
12 |
12 |
6 |
6 |
3 |
0 |
0 |
|
|
Tween 80 (drops) |
3 |
6 |
9 |
9 |
15 |
18 |
15 |
0 |
|
|
HLB value |
9.67 |
10.73 |
11.34 |
12.44 |
13.17 |
14.09 |
15.00 |
0.00 |
|
|
Time needed for interphase to reach 1cm (min) |
Group 1 |
Interphase did not reach 1cm after 120 minutes. |
58.00 |
61.00 |
45.00 |
25.00 |
0.50 |
||
|
Group 5 |
Interphase did not reach 1cm after 120 minutes. |
16.00 |
30.00 |
39.00 |
16.00 |
7.00 |
|||
|
Average |
– |
37.00 |
45.50 |
42.00 |
20.50 |
3.75 |
|||
|
Stability |
Yes |
Yes |
Yes |
No |
No |
No |
No |
No |
|
Arachis Oil
| Tube no. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||
| Span 20 (drops) | 15 | 12 | 12 | 6 | 6 | 3 | 0 | 0 | ||
| Tween 80 (drops) | 3 | 6 | 9 | 9 | 15 | 18 | 15 | 0 | ||
| HLB value | 9.67 | 10.73 | 11.34 | 12.44 | 13.17 | 14.09 | 15.00 | 0.00 | ||
| Time needed for interphase to reach 1cm (min) | Group 2 | Interphase did not reach 1cm after 120 minutes. | 27.00 | 40.00 | 55.00 | 19.00 | 9.00 | |||
| Group 6 | Interphase did not reach 1cm after 120 minutes. | 38.00 | 49.00 | 61.00 | 19.00 | 25.00 | ||||
| Average |
– |
– |
– |
32.50 | 44.50 | 58.00 | 19.00 | 17.00 | ||
| Stability | Yes | Yes | Yes | No | No | No | No | No | ||
Olive Oil
| Tube no. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
| Span 20 (drops) | 15 | 12 | 12 | 6 | 6 | 3 | 0 | 0 | |
| Tween 80 (drops) | 3 | 6 | 9 | 9 | 15 | 18 | 15 | 0 | |
| HLB value | 9.67 | 10.73 | 11.34 | 12.44 | 13.17 | 14.09 | 15.00 | 0.00 | |
| Time needed for interphase to reach 1cm (min) | Group 3 | Interphase did not reach 1cm after 120 minutes. | 8.19 | 14.48 | 87.35 | 58.35 | 19.49 | 0.33 | |
| Group 7 | Interphase did not reach 1cm after 120 minutes. | 63.00 | Interphase did not reach 1cm after 120 minutes. | 45.00 | 2.50 | ||||
| Average |
– |
75.18 | – | 32.25 | 1.42 | ||||
| Stability | Yes | Yes | No | No | No | No | No | No | |
Mineral Oil
| Tube no. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||
| Span 20 (drops) | 15 | 12 | 12 | 6 | 6 | 3 | 0 | 0 | ||||
| Tween 80 (drops) | 3 | 6 | 9 | 9 | 15 | 18 | 15 | 0 | ||||
| HLB value | 9.67 | 10.73 | 11.34 | 12.44 | 13.17 | 14.09 | 15.00 | 0.00 | ||||
| Time needed for interphase to reach 1cm (min) | Group 4 | 119.00 | 114.00 | 108.00 | 94.00 | 80.00 | 34.00 | 8.00 | 0.50 | |||
| Group 8 | Interphase did not reach 1cm after 120 minutes. |
50.00 |
24.00 | 28.00 | 29.00 | 15.00 | 18.00 | 0.50 | ||||
| Average |
– |
o | 66.00 | 61.00 | 54.5 | 24.50 | 13.00 | 0.50 | ||||
| Stability | Yes | No | No | No | No | No | No | No | ||||
An emulsion can be considered as stable if it takes longer duration for the phase separation to occur. Span 20 and tween 80 is the surface active agent that added into the emulsion to improve the stability of the emulsion. The amount of span20 and tween80 that needed to add depends on the stability that required for the emulsion. HLB system gives the guidelines for the selection of emulsifier and the amount that need to add to achieve the satisfactory stability. The HLB system assigns a numerical value for each of the emulsifier and known as HLB. HLB of the emulsifier is the balance of the size and strength of the hydrophilic (water-loving or polar) and the lipophilic (oil loving or non-polar) groups of the emulsifier.
An emulsifier that is lipophilic in character is assigned a low HLB number (below 9.0), and one that is hydrophilic is assigned a high HLB number (above 11.0). Those in the range of 9-11 are intermediate. Appropriate HLB value is important in determining the stability of the emulsion. Span is hydrophobic and it is used to make the w/o emulsion while tween is hydrophilic and is used to form o/w emulsion. In the stabilization of oil globules, it is essential that there is a degree of hydrophilicity to confer an enthalpic stabilizing force and a degree of hydrophobicity to secure adsorption at the interface. So, a combination of both offers a suitable HLB value which matches with the system and produces a stable emulsion.
For palm oil, arachis oil and olive oil, the HLB value that brings to stable emulsion is 11.34. This means that the stable emulsion of palm oil can be prepared by adding 12 drops of Span 20 and 9 drops of Tween 80. On the other hands, the HLB value of the mineral oil that can give stable emulsion is 10.73 which mean 12 drops of Span 20 and 6 drops of Tween 80 are required for the formation of stable emulsion. These can show that different types of oils as the dispersed phase required different HLB values of emulsifier. Thus it requires different combination of emulsifiers in order to obtain a stable emulsion.
From the experiment for arachis oil which is done by our group, it was found that the emulsion in test tube 1, 2 and 3 with the HLB values as 9.67, 10.73 and 11.34 respectively which can give the most stable emulsions. The phase separation for the emulsion in test tube 1, 2 and 3 do not occur after 120 minutes (2 hours) which means they require longer time for phase separation to occur. Thus we can conclude that they are the most stable emulsion with the HLB value that ranges from 9-13. Meanwhile, emulsions from tube 7 and 8 give the lowest stability where the phase separation time is the shortest. This is because the absence of surfactant as an emulsifying agent in tube 8 while in tube 7, only Tween 80 present and with a high HLB value that more than 11. HLB value that more than 11 means a hydrophilic emulsifier has been used and it unable to stabilize the emulsion.
From the experiment for palm oil, it was found that the emulsion from test tube 1, 2 and 3 with the HLB values as 9.67, 10.73 and 11.34 respectively give the most stable emulsions. The phase separation for the emulsion in test tube 1, 2 and 3 do not occur even after 120 minutes (2 hours), which means they require longer time for phase separation to occur. Thus we can conclude that they are the most stable emulsion with the HLB value that ranges from 9-13. However, the emulsions from tube 7 and 8 give the lowest stability where the phase separation time is the shortest. The reason is just the same as the above which is due to the absence of surfactant as an emulsifying agent in tube 8 while in tube 7, only Tween 80 present and with a high HLB value that more than 11. HLB value that more than 11 means a hydrophilic emulsifier has been used and it unable to stabilize the emulsion.
For the emulsion of olive oil in the experiment, emulsions from test tube 1 and 2 with HLB value 9.67 and 10.73 respectively have shown the most stable emulsion. Their interphase do not reach 1cm after 120 minutes (2 hours) which mean that they require a longer duration for the phase separation to occur. The emulsion in test tube 8 is the least stable emulsion since there is no emulsifier added into the emulsion to stabilize it. Thus the emulsion just dispersed less than 3 minutes and separate into 2 phases.
For the emulsion of mineral oil, the most stable emulsion is from the test tube 1 with the HLB value 9.67. The interphase of emulsion in test tube 1 do not reach 1cm after 2 hours which means that the emulsion is stable and allow the even dispersion of the oil globules in the water. As the same with the others emulsion of different oil, the emulsion from test tube 8 is the least stable due to the absence of the emulsifier. Phase separation of emulsion in test tube 8 is occurred as soon as the removal of swirling force.
2. Compare the physical appearance of arachis oil emulsion and give comment about it. What is Sudan III test? Compare the colour distribution in emulsions formed and give comments about it.
Sudan III test is a test using Sudan III which is oil soluble to show amount and location of lipids. Sudan III is also a fat-soluble dye used for staining of triglycerides in frozen sections, some protein bound lipids and lipoproteins on paraffin. Sudan III has the appearance of reddish brown crystals. It stained red in oil. . It is not water soluble. When the emulsion is oil in water, the Sudan III does not disperse in the emulsion because they will not mix together. While in the water in oil emulsion, the Sudan III colouring will disperse in the emulsion.
| Magnification (40×10) | Physical appearance | Colour distribution |
Test tube 1 |
Water droplets dispersed in oil. This is water in oil emulsion. This emulsion is not dispersing very well due to error. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 2 |
Water droplets dispersed best in oil. This is water in oil emulsion. HLB value of the emulsion in this test tube is not in the optimum range. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 3 |
Water droplets dispersed better in oil compared to test tube 1. This is water in oil emulsion. However, the HLB value of the emulsion in this test tube is not in the optimum range. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 4 |
Water droplets are not properly dispersed in oil. HLB value of the emulsion in this test tube is not in the optimum range. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 5 |
Water droplets are not properly dispersed in oil. HLB value of the emulsion in this test tube is not in the optimum range. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 6 |
Water droplets are not properly dispersed in oil. HLB value of the emulsion in this test tube is not in the optimum range. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 7 |
Water droplets are not properly dispersed in oil. HLB value of the emulsion in this test tube is not in the optimum range. | Sudan III colour dispersed in the emulsion. The emulsion stained light orange. |
Test tube 8 |
The emulsion is totally not formed without surfactant, phase separation occur very fast. | Sudan III does not disperse in the emulsion, globules of Sudan red form on surface of emulsion. |
3. Plot and discuss
|
Group |
Viscosity (cP) |
||||||
| Before the temperature cycle | After the temperature cycle | ||||||
| 20 | 1 | 80.0 | 90.0 | 100.0 | 90.0 | 100.0 | 100.0 |
| 5 | 100.0 | 110.0 | 120.0 | 130.0 | 140.0 | 140.0 | |
| 25 | 2 | 389.9 | 419.9 | 419.9 | 779.8 | 779.8 | 659.9 |
| 6 | 419.9 | 419.9 | 389.9 | 857.9 | 842.9 | 731.9 | |
| 30 | 3 | 239.9 | 210.0 | 210.0 | 539.9 | 449.9 | 389.9 |
| 7 | 50.0 | 60.0 | 50.0 | 50.0 | 50.0 | 50.0 | |
| 35 | 4 | 650.0 | 650.0 | 600.0 | 300.0 | 300.0 | 300.0 |
| 8 | 740.0 | 820.0 | 920.0 | 900.0 | 920.0 | 960.0 | |
i. Graph of sample viscosity before and after the temperature cycling vs the different content of oil.
|
Content of mineral oil (ml) |
Average Viscosity (cP) (Average ± SD) |
Difference Viscosity (%) (Average ± SD) |
|
|
Before the temperature cycle |
After the temperature cycle |
||
|
Palm oil (20) |
100.00±12.91 |
116.67±20.55 |
16.67% |
|
Arachis oil (25) |
409.90±199.51 |
775.37±66.63 |
89.16% |
|
Olive oil (30) |
136.65±83.98 |
254.95±209.53 |
86.57% |
|
Mineral oil (35) |
730±111.05 |
613.33±313.83 |
-15.98% |
The viscosity is the measure of internal friction in a liquid or the resistance to a flow. In the experiment, we use four different types of oil which are palm oil, arachis oil, olive oil, and mineral oil. Besides that, we also use different volume of each type of oil. In the experiment, the emulsion for each sample oil is heated at 45°C for 30 minutes then the emulsion is put into refrigerator for freezing at 4°C for 30 minutes. The exaggeration of the temperature fluctuations subjected to the emulsion is used to compare the physical instabilities of the emulsion under the normal stored condition. When the emulsion is heated and frozen, the small ice crystals will be formed continually. This will disrupts the adsorbed layer of the emulsifying agent at the oil-water interface. As a result, the weakness in the structure of the film will become more apparent quickly.
From the graph, the volume of oil is increased, the viscosity of emulsion will be increased. For example, the emulsion II has higher viscosity than emulsion I. Besides that, in which emulsion I (20 ml of turpentine oil) has the lowest viscosity before and after the temperature cycle. On the other hand, viscosity of the emulsion containing 35ml of mineral oil is the highest. For emulsion IV (35 ml of mineral oil), the viscosity of emulsion of before heating is higher than after heating.
Theoretically, the formation of ice crystal leads to the decrease in the viscosity of the emulsion. As the consequence, the sample viscosity before temperature cycling is actually higher than that of after temperature cycling. Besides that, the drop in the sample viscosity of the mineral oil after temperature cycling may be due to the occurrence of phase inversion. This means that the initially o/w emulsion is now converted into w/o emulsion. However, the graph obtained does not follow the pattern theoretically. This is due to errors while conducting the experiments. Some precautions was occurred, like we did not waiting until room temperature then directly measure the viscosity of emulsion. The temperature of emulsion is too low after take out from refrigerator. This cause the viscosity of emulsion is increasing.
ii. Graph of the viscosity difference (%) versus various amount of mineral oil
In this experiment, emulsion containing 25ml of arachis oil shows the greatest difference in the viscosity, that is 241.18%. The smallest difference in viscosity, which is 16.03%, is shown by the emulsion containing 35ml of mineral oil.
The higher the difference in viscosity, the less stable is the emulsion. From the results obtained in this experiment, emulsion with arachis oil is the most unstable emulsion while emulsion with mineral oil is the most stable one. However, emulsion with palm oil actually should have the smallest viscosity difference value and is the most stable one as it contains the least amount of palm oil. This is because when there is a higher oily phase present in an emulsion, the emulsion is actually becoming more unstable. Therefore, when these different types of emulsion are subjected to temperature cycling, the amount of ice crystals formed is usually directly proportional to the extent of the instability of the emulsion, or the volume of the oil used. The more the ice crystals are formed, the greater is the reduction in sample viscosity, and thus the greater is the viscosity difference (%). Therefore, emulsion with mineral oil is not the most stable emulsion. These show that errors occur during the experiment.
4. Plotting graph of Seperated Phase Ratio Against Different Type and Volume of Oil.
|
Readings |
Height (mm) |
|||||
|
Palm oil (20ml) |
Arachis oil (25ml) |
|||||
|
Group 1 |
Group 5 |
Average |
Group 2 |
Group 6 |
Average |
|
| Separation phase |
30 |
35 |
36 |
20 |
||
| Original emulsion |
49 |
48 |
46 |
39 |
||
| Height ratio |
0.61 |
0.73 |
0.67 |
0.78 |
0.51 |
0.645 |
|
Readings |
Height (mm) |
|||||
|
Olive oil (30ml) |
Mineral oil (35ml) |
|||||
|
Group 3 |
Group 7 |
Average |
Group 4 |
Group 8 |
Average |
|
| Separation phase |
35 |
37 |
29 |
30 |
||
| Original emulsion |
50 |
50 |
50 |
45 |
||
| Height ratio |
0.70 |
0.74 |
0.72 |
0.58 |
0.67 |
0.625 |
|
Mineral Oil (ml) |
Ratio of Phase separation (X± SD) |
|
Palm Oil (20 ml) |
0.67±0.06 |
|
Arachis Oil (25 ml) |
0.645±0.135 |
|
Olive Oil (30 ml) |
0.72±0.02 |
|
Mineral Oil (35 ml) |
0.625±0.045 |
Phase separation ratio is used to indicate stability of an emulsion. A high ratio of phase separation will be resulted in unstable emulsion which it will have two separated, non-homogenised phase. The non-homogenous emulsion is easily separated as compared with homogenous emulsion. The uniformity of drug in the emulsion will be altered and inaccurate dosage is being administered.
Based on the graph plotted, separated phase ratio decrease from 20mL mineral oil emulsion to 25mL mineral oil emulsion, increase from 25mL mineral oil emulsion to 30mL mineral oil emulsion and decrease from 30mL mineral oil emulsion to 35mL mineral oil emulsion. Emulsion with 30mL mineral oil by using olive oil has highest separated phase ratio while 35mL mineral oil emulsion has lowest separation phase ratio.
According to theory, as the amount of oil increase, the separated phase ratio will increase. This is because the added amount of oily phase in emulsion has exceeded the oil amount at which stable emulsion is formed. Therefore, separation will occur in a faster rate.
However, the results obtained from graph do not follow this theory. This may be due to several errors that occur during experiment. For example, inaccuracy in measuring amount of oil before forming the emulsion, insufficient homogenisation that has been carried out on emulsion or the height of separated phase is not measured accurately. Besides, if the volume of each test tube is not equal during centrifuge, the result of centrifuge will be inaccurate. Using of wrong method of preparation of emulsion, that is, the wet gum method may affect the result too. If good emulsion is failed to be produced, it will affect stability of emulsion which will then affect the result of the experiment.
5. What is the function of each ingredient used in the emulsion preparation? How can the different amount of ingredients influence the physical characteristics and the stability of the emulsion?
|
Function |
Note |
|
| Palm oil, Arachis oil, Olive oil and mineral oil | The oily phase in the o/w emulsion. | Amount of the mineral oil (oily phase) and the distilled water (aqueous phase) used is important to determine the type of emulsion formed, whether o/w or w/o emulsion. The volume of the dispersed phase should not be more than the volume of the continuous phase. Or else, phase inversion will occur. |
| Acacia | It is a natural product and it can act as an emulsifying agent which can reduces the interfacial tension and maintains the separation of the droplets in the dispersed phase. Acacia which acts as the emulsifying agent should be used in appropriate amount according to the HLB value. If the inappropriate HLB value used, the large interfacial tension between the dispersed phase and the continuous phase formed and the separation of phase will occur. | Since acacia is a natural product, it can be a good medium for the growth of microorganisms.Thus, agent antimicrobial such as benzoic acid 0.1% is added to stabilize the emulsion from microbial growth. It is different from the surfactant which reduce the surface tension. |
| Syrup | Increase the viscosity of the emulsion and acts as sweetening agent that used to mask the unpleasant taste of the mineral oil in order to increase the patient compliance. Moreover, it can be used to increase the viscosity of the emulsion since it is a viscous liquid. Therefore the amount of syrup that added into the emulsion has to be controlled to ensure the suitable viscosity of emulsion. | Viscosity of the emulsion will affect on the physical stability and the rheological characteristic of the emulsion. We have to consider the ease of pouring out the emulsion from the container. Therefore, the viscosity of the emulsion has to be strictly monitored to avoid the rheological problem. |
| Vanillin | As flavoring agent which can improve the taste of emulsion thus can increase patient compliance. | Mostly emulsion has a bad taste that most of the patient unable to accept. Vanillin aids in the taste of emulsion. |
| Alcohol | Alcohol is an antimicrobial agent. In this formulation, alcohol acts as a preservative but the amount of alcohol used should not too high to prevent toxicity occur. | In this formulation, there is a high proportion of water present in the emulsion which making it more susceptible to microbial contamination. A suitable antimicrobial agent should be used to prevent instability of emulsion. |
| Distilled water | It is the continuous phase in the emulsion in which the oily phase is homogenously dispersed with the aid of the surfactants. | The distilled water which is the aqueous phase and the oils which is the oily phase in the emulsion, thus the amount of each phase or the volume ratio in certain emulsion is determined by the desired type of emulsion, either o/w or w/o emulsion. |
Conclusion:
The combination of different surfactants will results in an accurate HLB value that is required to form a stable emulsion. Furthermore, different types of emulsifying agent will results in emulsion with different physical characteristics and stability. Emulsifying agent adsorb onto the oil and water interface thus lowering the surface interfacial tension which then in turn will lower the free energy of the system hence stabilizing the emulsion.
Reference:
1. Aulton, M.E. 1998. Pharmaceutics: The science of dosage form design. Edinburgh: Churchill Livingstone.
2. Shariza, Rudy, Ng Shiow Fern, Thomas. 2011. Pharmacy Practice: Guide to Compounding and Dispensing. Penerbit UKM: UKM Press.
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