to ensure that the speed and time settings match the formulation guidelines.

4.1.2.2 Calibrate the pH meter using standard buffer solutions (pH 4.0, 7.0, and 10.0).

4.2 Selection of Components

The components of a pH-responsive emulsion must be selected carefully to ensure stability and responsiveness to pH changes. Follow these steps to select the appropriate ingredients:

• 4.2.1 Select the oil phase (e.g., mineral oils, triglycerides) based on the solubility of the active ingredient and the desired emulsion type (oil-in-water or water-in-oil).
• 4.2.2 Choose emulsifiers with an appropriate hydrophilic-lipophilic balance (HLB) value, typically 8-18 for oil-in-water emulsions and 3-6 for water-in-oil emulsions.
• 4.2.3 Incorporate pH-responsive agents, such as polyelectrolytes or pH-sensitive polymers, to enable controlled release in response to pH changes.

4.3 Emulsion Preparation Process

4.3.1 Preparation of the Oil and Water Phases

• 4.3.1.1 Weigh the required amounts of oil phase and aqueous phase ingredients as per the formulation protocol. Record the weights in the Batch Manufacturing Record (BMR).
• 4.3.1.2 Dissolve the emulsifiers and pH-sensitive agents in the appropriate phase (usually the aqueous phase) and heat to the required temperature (typically 40°C-60°C).
• 4.3.1.3 Heat the oil phase separately to the same temperature using a temperature-controlled water bath.

4.3.2 High-Shear Mixing Process

• 4.3.2.1 Set up the high-shear mixer and adjust the speed, time, and temperature settings according to the formulation guidelines.
• 4.3.2.2 Slowly add the oil phase to the aqueous phase while continuously mixing at a controlled speed.
• 4.3.2.3 Continue mixing until a stable, homogeneous emulsion is formed. If necessary, use an ultrasonicator to reduce the droplet size.
• 4.3.2.4 Monitor the temperature throughout the process to prevent phase separation or destabilization.

4.4 Quality Control Testing of pH-Responsive Emulsions

Once the pH-responsive emulsion is prepared, it must undergo quality control tests to ensure it meets the required specifications for droplet size, stability, and pH-sensitive release. The following tests are recommended:

• 4.4.1 Measure the droplet size of the emulsion using a droplet size analyzer. The droplet size should typically range from 100 nm to 5 µm.
• 4.4.2 Conduct pH-release testing by exposing the emulsion to different pH conditions (e.g., pH 3.0, 5.0, and 7.0) and monitoring the rate of drug release.
• 4.4.3 Perform stability testing by storing the emulsion at room temperature and under accelerated conditions to assess phase separation and droplet size retention.
• 4.4.4 Check the pH of the emulsion using a calibrated pH meter to ensure it meets the formulation specifications.

4.5 Storage of pH-Responsive Emulsions

The prepared pH-responsive emulsion should be stored in sterilized, airtight containers. Label the containers with the batch number, preparation date, and storage conditions. Store the emulsion at the recommended temperature, typically 4°C or room temperature, and periodically test for stability and droplet size retention.

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)
• Droplet Size Analysis Report
• pH Release Test Report
• Stability Test Report

7) References, if any

• ICH Q7: Good Manufacturing Practice Guidelines
• FDA Guidance for pH-Sensitive Drug Delivery Systems

8) SOP Version

Version 1.0

Annexure

Annexure 1: Batch Manufacturing Record Template

 
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Batch No.
    
Oil Phase
    
Water Phase
    
Emulsifier Type
    
pH-Responsive Agent
    
Mixing Time
    
Operator Initials
    
QA Signature
  
  

    
Batch Number
    
Oil Type/Weight
    
Water Type/Volume
    
Emulsifier Name
    
pH-Sensitive Polymer/Weight
    
Minutes
    
Operator Name
    
QA Name