1. Mixing and Homogenization Lab (1) Shahen S. Mohammed MSc pharmaceutics
University of Sulaimani College of Pharmacy 5th Stage Practical Industrial Pharmacy 7
Mixing and Homogenization
Lab (1)
Shahen S. Mohammed
MSc pharmaceutics

2. Mixing
Mixing can be defined as the process in which two or more than two components in a separate or roughly mixed condition are treated in such a way so the each particle of any one ingredient lies as nearly as possible to the adjacent particles of other ingredients or components.

3. Mixing may be done for following reasons:
To ensure uniformity of composition between the mixed ingredients.
To initiate or to enhance the physical or chemical reactions like diffusion and dissolution.

4. Types of mixture
Positive mixtures
Negative mixing
Neutral mixtures

5. Types of mixture
1. Positive mixtures: it’s formed when two or more than two gases or miscible liquids are mixed together by means of diffusion process. In this case no energy is required, proved the time allowed for solution formation is sufficient, generally these types of material don’t create any problem in mixing.

6. 2. Negative mixing: These types of mixtures are formed when insoluble solids are mixed with a vehicle to form a suspension or when two immiscible liquid are mixed to form an emulsion. These mixtures are more difficult to prepare and require a higher degree of mixing with external force. The component of these mixtures separate out unless they are continuously stirred.

7. 3. Neutral mixtures: many pharmaceutical products such as pastes, ointments and mixed powders are the examples of neutral mixtures. The components of such products don’t have any tendency to mix spontaneously but once mixed, they don’t separate out easily.

8. Homogenization: it’s the process in which a coarse emulsion is converted into a colloidal state of uniform composition by reducing the size of the particles so that each measured dose should have same composition. This process is used for the preparation of suspension, emulsion.

9. Homogenizers: they are based on the principle that when large globules in coarse emulsion are passed, under pressure, through a narrow orifice are broken into smaller globules having a greater degree of uniformity and stability.

10. Powder mixing: it’s a neutral type of mixing
Powder mixing: it’s a neutral type of mixing. It is one of the most common operations employed in pharmaceutical industries for the preparation of different types of formulations like powder, capsules and tablets.

11. Mixing factors
Physical properties
Before powder mixing

12. Mixing factors Volume Mixing mechanism Duration of mixing
Handling of the mixed powders

13. Proportions of materials to be mixed
Physical properties
Density
Particle size
Particle shape
Proportions of materials to be mixed

14. Before powder mixing the following factors should be concerned:
Mixing factors
Volume: the mixer must not be filled to the brim. Overfilling of the mixer reduces the efficiency and sometimes mixing may be entirely prevented.
Mixing mechanism.
Duration of mixing.
Handling of the mixed powders: bulk powder should be remixed before its use because after mixing separation of ingredients may be happen as a result of vibration during transport.

15. Physical properties
Density: if the densities of mixing ingredients are different it is quite difficult to mix them thoroughly.
Particle size: substances with different particles size are difficult to mix and may lead to segregation.
Particle shape: spherical shape of particles is ideal for mixing the powders and any deviation from this shape leads to difficulty in mixing, but on the other hand particles with irregular shapes can interlock with each other therefore chances of segregation are minimized once mixing has been done.
Proportions of materials to be mixed: it’s easy to mix the powders if they are available in equal quantities.

16. Experiment
Aim: Examine the efficiency of mixing of mechanical method (Rotary Laboratory mixer)
Instruments:
• Rotary Laboratory mixer
• Balance
• Oven
Chemicals:
• Sand particles
• NaCl powder

17. Part 1. Machine
1. Weigh 250 gm of NaCl and 250 gm of sand using a balance, the machine is switched on and he rotation and the time of mixing is set up.
2. The pre-weighed amount of the powders are added to the machine and then mixed for 15 minutes.
3. Each group will take samples of 10 gm from the mixture. The samples are examined for the degree of mixing.

18. Part 2. Sample preparation.
a. The whole sample is dissolved in an amount of water in order to dissolve all the salts in the sample
b. After the dissolving has been accomplished. The amount of sample left is filtered through a filter paper.
c. The remaining sand ( on the filter paper) is placed in an oven at 80 C and left until it is dried (20 minutes)
d. The dried sample is weighed and the percentage of mixing is determines form the following equation :