1. SCS Summer School 2017
Past Exam Question
Russell Cox

2. 2016 Emulsion Exam Question
Read the question fully before starting to write your answers
Look at the allocation of marks for particular sections of the question

3. 2016 Emulsion Exam Question

4. a;
There are 3 types of physical properties used to define emulsions; Fundamental, Macroproperties and Microproperties. What does each of the properties describe about an emulsion? (3)

5. a; What does each of the properties describe about an emulsion?
Fundamental properties;
The basic properties of the emulsion system before and during the mixing process
Macro properties;
Properties that deal with the prepared emulsion as a whole
Micro properties;
Intrinsic attributes of the dispersed droplets

6. b;
For each of the properties give 2 examples of the attributes? (6)

7. b; For each of the properties give 2 examples of the attributes?
fundamental properties;
emulsifier type and quantity,
phase ratio,
phase refractive
properties index,
phase density,
phase viscosity,
electrolyte concentration of the water phase,
order of mixing,
energy input of mixing

8. b; For each of the properties give 2 examples of the attributes?
macro properties:
appearance,
viscosity,
density,
pH,
rheological properties

9. b; For each of the properties give 2 examples of the attributes?
micro propeties;
particle type,
particle size,
particle charge,
dispersed phase density,
dispersed phase viscosity,
dispersed phase refractive index,
continuous phase density,
continuous phase viscosity,
continuous phase refractive index.

10. c;
What are the 2 fundamental processes that must occur for an emulsion to become unstable? (2)

11. c;
What are the 2 fundamental processes that must occur for an emulsion to become unstable? (2)
physical attraction between droplets
coalescence of droplets

12. d;
For each process describe 2 examples of how you would overcome the processes leading to instability? (4)

13. d;
For each process describe 2 examples of how you would overcome the processes leading to instability?
Physical attraction;
Reduce attraction forces -eg introduce charge repulsion between droplets, by adding stearic acid or electrolytes
Reduce the ability for the droplets to move freely; increase viscosity, using viscosity modifiers or waxes and gums
Coalescence
Strengthen the interface of the droplet using polymers
Strengthen the interface of the droplet using powders
Alter the surface characteristics of the droplet using surfactants and emulsifiers

14. e;
Describe 5 methods you would use to assess the stability of an emulsion, giving an explanation what the results would indicate with respect to the formulation? (10)

15. e;
Describe 5 methods you would use to assess the stability of an emulsion, giving an explanation what the results would indicate with respect to the formulation?
Accelerated ageing - changes in parameters indicate poor long term stability under "ambient" conditions or product will not tolerate extreme conditions
Freeze/thaw – indicates commercially acceptable stability, failure would indicate potential problems if the product is ever frozen or exposed to frost during storage, transportation or use
Rapid stability screening -centrifuge, sonication etc gives a quick assessment as to the long term stability of the product

16. e;
Describe 5 methods you would use to assess the stability of an emulsion, giving an explanation what the results would indicate with respect to the formulation?
Packaging - interactions between packaging and product. fluctuations indicate wrong choice of packaging, or leaching of chemicals between the packaging and formulation
Microbial testing - failure indicates preservation system isn’t up to the task, alternative preservation required
Microscopy -monitor particle size, any significant indicate early coalescence

17. e;
Describe 5 methods you would use to assess the stability of an emulsion, giving an explanation what the results would indicate with respect to the formulation?
Visual assesment -compare light and dark samples -indicates poor photostabiity of the product
pH -check the pH level of the formulation to determine if the system is chemically stable. fluctuations indicate one or more of the ingredients may be decomposing under the normal conditions
Low shear evaluation – stirring/shaking over several days. Accelerates any phase separation that may occur in the emulsion

18. e;
Describe 5 methods you would use to assess the stability of an emulsion, giving an explanation what the results would indicate with respect to the formulation?
Retained samples -legal requirement for every batch of product. True test of long term storage