Emulsions: Preparation & Stabilization: Labs

Laboratory Procedure

A. Effect of Surfactant HLB on Emulsion Stability

1. Mark all tubes with a grease pencil 3 mm above the bottom curvature of the test tube.
2. Measure about 50 ml of peanut oil and add a small quantity of RED Lake Dye, 40%. Vortex.
3. To each of 8 test tubes, add 5 ml peanut oil and 5 ml distilled water.
4. Add drops of Tween^® 20 (polyoxyethylene sorbitan monolaurate) to the tubes as indicated in the Part A table.
5. Add drops of Span^® 85 (sorbitan trioleate) to the tubes as indicated in the Part A table.
6. Cover the tubes with parafilm and mix on a Vortex mixer for 30-45 seconds.
7. Record the time required for the interface to rise to the grease pencil mark. Rank the tubes from 1 (longest time, most stable) to 8 (shortest time, least stable).
8. Calculate the HLB value for the surfactant system in each tube.

 View a video demonstration on the emulsion experiment

B. Effect of Surfactant Concentration of Emulsion Stability

Repeat the steps in Part A, but using the amounts of Span and Tween as indicated in the Part B table.

C. Preparation and Evaluation of Emulsions
1. Preparation by Dry Gum Method

1. Using the dry gum method, prepare 50 ml of Mineral Oil Emulsion, NF by the formula given in Remington’s. Put in 2 oz. Rx bottle.
2. Using a hand homogenizer, homogenize half of the emulsion.

   

3. Stain a sample of both the homogenized and manually formed emulsions with amaranth solution and examine under a microscope. Draw a sketch of what you see and compare the globule shape and size distribution of the two emulsions.

2. Preparation by Wet Gum Method

1. Using the wet gum method, prepare 50 ml of Mineral Oil Emulsion, NF by the formula given in Remington’s. Put in 2 oz. Rx bottle.
2. Using a hand homogenizer, homogenize half of the emulsion.
3. Stain a sample of both the homogenized and manually formed emulsions with amaranth solution and examine under a microscope. Draw a sketch of what you see and compare the globule shape and size distribution of the two emulsions. Compare each to their counterparts to the emulsions prepared by the dry gum method.

View a video demonstration on preparation by dry and wet gum method

3. Preparation by Bottle (Forbes) Method

1. Using the bottle method, prepare 50 ml of an emulsion by shaking equal volumes of olive oil and lime water in a 3 oz. bottle.
2. Determine the type of emulsion formed by performing a dilution test on a 5-10 ml sample of the emulsion, and a dye test.
3. Add 4-5 ml of 4N HCl solution to 25 ml of the emulsion and record any changes observed.

4. Preparation by Beaker Method

1. Using the beaker method, prepare the following emulsion and put in a 4 oz. bottle:
   

   Mineral Oil	20 ml
   Tween 80 (polyoxyethylene sorbitan monooleate)	4 ml
   Span 85 (sorbitan trioleate)	2 ml
   Purified water	74 ml

2. Using a hand homogenizer, homogenize half of the emulsion.
3. Stain a sample of both the homogenized and manually formed emulsions with amaranth solution and examine under a microscope. Draw a sketch of what you see and compare the globule shape and size distribution of the two emulsions.

I. Prelab Data

See HLB values table in Remington’s

HLB Tween 20 (polyoxyethylene sorbitan monolaurate) = ____________

HLB Tween 80 (polyoxyethylene sorbitan monooleate) = ____________

HLB Span 85 (sorbitan trioleate) = ______________

Give the formula for 50 ml Mineral Oil Emulsion, NF

II. Experimental Data and Results

Part A. Effect of Surfactant HLB on Emulsion Stability

* note minutes/seconds elapsed before first signs of phase separation observed

Part B. Effect of Surfactant Concentration on Emulsion Stability

* note minutes/seconds elapsed before first signs of phase separation observed

Comments (parts A & B):

Part C. Preparation and Evaluation of Emulsions

1. Dry Gum Method

Comments:

2. Wet Gum Method

Comments:

Comparison of formulation outcomes of wet and dry gum methods:

3. Bottle Method

1. Describe the tests you used to determine the type of emulsion formed (o/w vs. w/o) and the results of those tests. (Sketch observations where applicable).
2. Record any changes noted when 4N HCl was added to the emulsion.

4. Beaker Method

Describe how you prepared the emulsion and any problems you encountered.

Comments:

Inspection of final products ______________________________

III. Discussion and Conclusions

1. What appears to be the HLB range that produces that most stable peanut oil emulsion in Part IIA? Are these the results you expected? Explain.

2. What effect did tripling the surfactant concentration have on the physical stability of the emulsions? How would you explain this?

3. What effect did homogenization have on the stability of your emulsions?

4. The lime water-olive oil emulsion you prepared is an example of “in situ” emulsifier formation.

1. What does this mean?
2. What is the emulsifier that is formed in this product?

5. What is the HLB of the emulsifying system used in the “beaker method” emulsion?