4.1.1 Required Equipment

• High-shear mixer
• Magnetic stirrer
• pH meter
• Temperature-controlled water bath
• Homogenizer (for finer emulsion preparation)
• Particle size analyzer

4.1.2 Equipment Calibration

• 4.1.2.1 Ensure that the high-shear mixer is calibrated for speed and time settings as per the formulation protocol.
• 4.1.2.2 Verify the calibration of the pH meter using standard buffer solutions (pH 4.0, 7.0, and 10.0).

4.2 Selection of Surfactants

The selection of surfactants is based on the type of emulsion being prepared (O/W, W/O, or multiple emulsion), the hydrophilic-lipophilic balance (HLB) of the surfactant, and the properties of the oil and water phases. Follow these steps for surfactant selection:

• 4.2.1 Determine the type of emulsion being formulated (e.g., O/W or W/O).
• 4.2.2 Select a surfactant with the appropriate HLB value. For O/W emulsions, use a surfactant with a higher HLB (8-18), while for W/O emulsions, use a surfactant with a lower HLB (3-6).
• 4.2.3 Consider the compatibility of the surfactant with the active ingredients and other excipients in the formulation.
• 4.2.4 Use a combination of surfactants (e.g., emulsifier and co-emulsifier) if necessary to achieve the desired stability and droplet size.

4.3 Preparation of Emulsion

Once the surfactants are selected, the emulsion can be prepared by mixing the oil and water phases under controlled conditions. The following steps outline the emulsion preparation process:

4.3.1 Preparation of the Oil and Water Phases

• 4.3.1.1 Weigh the required amounts of the oil phase (e.g., oils, lipids) and water phase (e.g., water, hydrophilic components) according to the formulation protocol. Record the weights in the Batch Manufacturing Record (BMR).
• 4.3.1.2 Dissolve the surfactant(s) in the appropriate phase (oil or water) as specified by the formulation protocol. For example, hydrophilic surfactants should be dissolved in the water phase, while lipophilic surfactants should be dissolved in the oil phase.
• 4.3.1.3 Heat both phases separately to the specified temperature (typically 60°C-80°C) using a temperature-controlled water bath.

4.3.2 Emulsion Formation

• 4.3.2.1 Slowly add the oil phase to the water phase while mixing continuously with a high-shear mixer.
• 4.3.2.2 Continue mixing at a controlled speed to form a coarse emulsion. Maintain the temperature throughout the process to ensure proper mixing.
• 4.3.2.3 Once a coarse emulsion is formed, transfer the mixture to a homogenizer for further size reduction if finer droplets are required.

4.4 Quality Control Testing of Emulsion

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

• 4.4.1 Measure the particle size of the emulsion using a particle size analyzer to confirm that the droplet size is within the desired range (typically 100 nm to 10 μm).
• 4.4.2 Evaluate the stability of the emulsion by monitoring its phase separation or creaming over time. Store the emulsion at room temperature and at accelerated conditions to assess its stability.
• 4.4.3 Check the pH of the emulsion using a calibrated pH meter to ensure it is within the acceptable range for the product (e.g., pH 4.5-7.5).
• 4.4.4 Perform viscosity measurements if necessary to ensure the emulsion has the appropriate flow properties for its intended use (e.g., topical creams or injectable emulsions).

4.5 Storage of Emulsion

The emulsion should be stored under appropriate conditions to maintain its stability. Transfer the emulsion to sterilized, airtight containers, and label each container with the batch number, preparation date, and storage conditions. Store the emulsion at the recommended temperature (e.g., 4°C or room temperature), and periodically test its stability and homogeneity over time.

5) Abbreviations, if any

• O/W: Oil-in-Water
• 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 Topical and Injectable Emulsions

8) SOP Version

Version 1.0

Annexure

Annexure 1: Batch Manufacturing Record Template

  

    
Batch No.
    
Surfactant Type
    
Oil Phase
    
Water Phase
    
HLB Value
    
Mixing Time
    
Operator Initials
    
QA Signature
  
  

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