4.2 Preparation of Water-in-Oil Emulsion

The following steps outline the process for preparing W/O emulsions, from selecting ingredients to forming the emulsion:

4.2.1 Selection and Weighing of Ingredients

• 4.2.1.1 Weigh the required amounts of oil phase ingredients (e.g., oils, lipids) and water phase ingredients (e.g., water, hydrophilic components) according to the formulation protocol. Record the weights in the Batch Manufacturing Record (BMR).
• 4.2.1.2 Select the appropriate emulsifier(s) with low hydrophilic-lipophilic balance (HLB) values (typically 3-6) for W/O emulsions.

4.2.2 Preparation of Oil and Water Phases

• 4.2.2.1 Heat the oil phase ingredients (e.g., oils, waxes) in a temperature-controlled water bath to 60°C-80°C to melt and homogenize them.
• 4.2.2.2 Heat the water phase ingredients in a separate beaker to the same temperature as the oil phase.
• 4.2.2.3 Dissolve the emulsifier(s) in the oil phase, as required by the formulation protocol.

4.2.3 Formation of Water-in-Oil Emulsion

• 4.2.3.1 Slowly add the water phase to the oil phase while continuously mixing with a high-shear mixer.
• 4.2.3.2 Maintain the mixing speed as per the formulation protocol to form a coarse emulsion.
• 4.2.3.3 For finer emulsions, pass the mixture through a homogenizer after the coarse emulsion is formed.

4.3 Quality Control Testing of W/O Emulsion

After the emulsion is prepared, it must undergo quality control testing to ensure it meets the required specifications for droplet size, stability, and homogeneity. Perform the following tests:

• 4.3.1 Measure the droplet size of the emulsion using a particle size analyzer to confirm the size is within the desired range (typically 100 nm to 10 μm).
• 4.3.2 Evaluate the stability of the emulsion by monitoring phase separation or creaming over time.
• 4.3.3 Check the pH of the emulsion using a calibrated pH meter to ensure it is within the acceptable range.
• 4.3.4 Perform viscosity measurements to ensure the appropriate flow properties for the intended application (e.g., ointments or topical products).

4.4 Storage of Water-in-Oil Emulsion

Transfer the emulsion to sterilized, airtight containers and label them with the batch number, preparation date, and storage conditions. Store the emulsion at the recommended temperature and periodically assess its stability.

5) Abbreviations, if any

• W/O: Water-in-Oil
• HLB: Hydrophilic-Lipophilic Balance
• QA: Quality Assurance
• QC: Quality Control

6) Documents, if any

• Batch Manufacturing Record (BMR)
• Particle Size Analysis Report
• Stability Test Report
• pH Calibration Log

7) References, if any

• ICH Q7: Good Manufacturing Practice Guide
• FDA Guidelines for Emulsions

8) SOP Version

Version 1.0

Annexure

Annexure 1: Batch Manufacturing Record Template

  

    
Batch No.
    
Oil Phase
    
Water Phase
    
Emulsifier Type
    
Mixing Time
    
Homogenization Time
    
Operator Initials
    
QA Signature
  
  

    
Batch Number
    
Oil Type/Weight
    
Water Type/Volume
    
Emulsifier Name
    
Minutes
    
Minutes
    
Operator Name
    
QA Name