PHM2213 practical
106752546
PHM 2213 Physical Pharmacy 2
Preparation of oil-in-water emulsion
NOTE
Students will be divided into groups. Although experimental work will be carried out
in a group, reports shall be submitted individually.
OBJECTIVE
This practical aims to allow students to understand the concept of emulsification by
using different types of surfactants and the method to determine emulsion stability
and properties and relate them to known theories.
INTRODUCTION
Emulsions have several advantages as drug delivery systems. For example, they offer
opportunities for solubilising relatively large amounts of hydrophobic substances,
with advantages relating to e.g. the effective drug solubility, the drug release rate, and
the drug chemical stability, Furthermore, the amount of surfactants required are
generally quite low, and relatively non-toxic surfactants such as phospholipids can be
used as emulsifiers.
Since oil and water do not mix, oil-water mixtures eventually separate into two
macroscopic phases. Thus, emulsions are thermodynamically unstable systems. In
order to form emulsions which are useful for drug delivery, their kinetic
destabilisation must generally be slowed down by the use of different surface active
agents. These may also help forming the emulsion and to reach a sufficiently small
droplet size.
The formation of emulsion systems is a complex process which involves generation
and stabilisation of new oil-water interface. In drug delivery, high pressure
homogenization is frequently used for generating new surface, and for producing
emulsion droplets. Within high pressure homogenization, the liquid mixture is passed
through a chamber where turbulent motions are generated. This, in turn, generates
shear forces, which ‘tear apart’ any large entities in the system, and result in droplet
formation.
The size of the oil droplets formed depend on the intensity of emulsification i.e. the
homogenization speed and period, temperature of the emulsification, ratio of the oil
and water phases, type and dosage of the surfactants used and the geometry of the
homogenization chamber. Indeed, the role of the surfactant is to reduce the interfacial
tension and promote droplet formation and to stabilize the emulsion droplets from
flocculation and coalescence.
Prepared by: Kausar Ahmad
Date created: 13-May-2004
Date of revision: 31-December-2004
Page 1 of 4
PHM2213 practical
106752546
EXPERIMENTAL PROCEDURE
Note:
The emulsions prepared in this practical will be used for subsequent practical
sessions.
Please keep the remaining emulsions at 30C. Label them:
Course code
Name of group leader
Type of emulsion
Date prepared
1. Preparation of phases for oil-in-water emulsion
Weigh 200 g of palm oil/sunflower oil/canola oil/olive oil or otherwise given in a
beaker. Weigh 600 g of distilled water in a one litre glass beaker. Ensure that the
beakers are dry and free from contaminant.
Prepare four emulsions:
(i)
without any surfactant
(ii)
non-ionic surfactant: 10% w/w
(iii)
anionic surfactant : 10%
(iv)
a combination of 5% non-ionic and 5% anionic surfactants
Add the surfactants to either the oil phase or the water phase, depending on their
compatibility. The amount of surfactants to be added is based on the amount of oil.
Keep at 30C.
Note
To check the compatibility, try to dissolve a small amount of surfactant in oil and in water. Although
not exclusive, emulsifiers can be selected based on Bancroft’s rule to produce either an oil-in-water
emulsion or vice versa. Further, the hydrophilic-lipophilic balance (HLB) can be used as a guide to
predict emulsion formation.
2. Homogenisation
Immerse the homogenizer head into the water phase. Note the model of the
homogenizer and record. Set the homogenizer speed at 4000 rpm or as allowed,
depending on the equipment capability. Turn on the unit and add the oil phase. Turn
the unit off after 10 minutes.
Please confirm that the homogenizer head is completely immersed to avoid inclusion
of air.
3. Phase separation
Pour each emulsion formed into a 100 ml graduated cylinder. Keep at 30C. Observe
the phase separation after 5 min, 10 min, 0.5, 1, 2 and 24 hours and record. Compare
the extent of phase separation for the different emulsions produced.
Prepared by: Kausar Ahmad
Date created: 13-May-2004
Date of revision: 31-December-2004
Page 2 of 4
PHM2213 practical
106752546
4. Microscopy
Take a picture of your emulsions immediately after preparation. One picture
should contain at least 50 particles. Include the scale in the picture (this will allow
you to calculate the size of your particles and compare to pictures that are to be
taken later).
RESULTS AND DISCUSSION
Tabulate your results in the following manner:
Table 1 Types of emulsions
Emulsion No.
Type of oil phase
Oil concentration (% w/w)
Surfactant type
Surfactant name
Surfactant concentration (%
w/w)
Table 2-1 Phase separation for emulsion no. 1
5 min
10 min
0.5 h
Oil phase
Cream phase
Emulsion phase
Water phase
Remarks
Table 2-2 Phase separation for emulsion no. 2
5 min
10 min
0.5 h
Oil phase
Cream phase
Emulsion phase
Water phase
Remarks
Table 2-3 Phase separation for emulsion no. 3
5 min
10 min
0.5 h
Oil phase
Cream phase
Emulsion phase
Water phase
Remarks
Table 2-4 Phase separation for emulsion no. 4
5 min
10 min
0.5 h
Oil phase
Cream phase
Emulsion phase
Water phase
Remarks
Prepared by: Kausar Ahmad
Date created: 13-May-2004
Date of revision: 31-December-2004
Page 3 of 4
1h
2h
24 h
1h
2h
24 h
1h
2h
24 h
1h
2h
24 h
PHM2213 practical
106752546
Write a report and submit one week after the practical.
Plot your results based on Table 2-1 to 2-4 and answer the following in your
discussion:
1.
2.
3.
4.
What are the roles of surfactants?
How does the surfactant impart stability?
What is the effect of surfactant concentration on emulsion stability?
What is the effect of homogenization conditions on the stability of the
emulsions?
a. emulsifying duration
b. shear rate or homogenizing speed
c. emulsifying temperature
5. From your results, what are the stabilisation and destabilization mechanisms
involved for each emulsion? Explain.
Prepared by: Kausar Ahmad
Date created: 13-May-2004
Date of revision: 31-December-2004
Page 4 of 4