formulation integrity over shelf-life.

2. Scope

This SOP applies to the Analytical Method Development (AMD) team responsible for evaluating the physical and chemical stability of oil-in-water (O/W) and water-in-oil (W/O) emulsions during development, optimization, and stability studies.

3. Responsibilities

• Analytical Scientist: Executes the emulsion stability testing procedure and documents results.
• QC Analyst: Supports in sample labeling, conditioning, and monitoring at intervals.
• QA Executive: Reviews all data, test reports, and ensures regulatory compliance with validated protocols.

4. Accountability

The Head of Analytical Method Development is accountable for the scientific soundness, validation, and regulatory alignment of the emulsion stability evaluation method.

5. Procedure

5.1 Parameters for Stability Evaluation

1. Physical appearance (phase separation, creaming, color change)
2. Globule/droplet size measurement
3. pH determination
4. Viscosity measurement
5. Zeta potential (optional for ionic emulsions)

5.2 Sample Preparation

1. Mix the emulsion sample thoroughly before testing to ensure uniformity.
2. Dispense required volumes for analysis and storage in respective stress chambers.

5.3 Storage Conditions for Accelerated Testing

• Long-term: 25°C ± 2°C / 60% RH ± 5%
• Accelerated: 40°C ± 2°C / 75% RH ± 5%
• Refrigerated: 5°C ± 3°C
• Freeze-thaw cycles: -20°C to 25°C, 6 cycles

5.4 Evaluation Time Points

• 0 (Initial), 1 week, 2 weeks, 1 month, 3 months, and 6 months

5.5 Droplet Size Measurement

1. Use laser diffraction or optical microscopy for droplet size analysis.
2. Record D10, D50, and D90 values at each time point.
3. Document presence of bimodal distribution or coalescence.

5.6 pH and Viscosity Monitoring

1. Measure pH using a calibrated pH meter (Annexure-2) at each interval.
2. Measure viscosity using a Brookfield viscometer with appropriate spindle at 25°C.

5.7 Physical Observation

1. Inspect visually for:
   • Phase separation
   • Creaming or sedimentation
   • Color change
   • Odor change
2. Document observations in the Stability Observation Log (Annexure-1).

5.8 Acceptance Criteria

• No phase separation, no significant creaming after 3 months at accelerated condition
• Droplet size change < ±10% over baseline (D50)
• pH change within ±0.5 units of initial value
• Viscosity variation within ±15%

5.9 Method Validation

1. Repeatability: RSD ≤ 5% for droplet size and viscosity measurements
2. Robustness: Stability observed under light exposure, agitation, and varying temperature

6. Abbreviations

• O/W: Oil in Water
• W/O: Water in Oil
• RH: Relative Humidity
• RSD: Relative Standard Deviation

7. Documents

1. Stability Observation Log – Annexure-1
2. pH and Viscosity Measurement Log – Annexure-2
3. Validation Summary Report – Annexure-3

8. References

• ICH Q1A(R2): Stability Testing of New Drug Substances and Products
• USP <729>: Globule Size Distribution in Lipid Injectable Emulsions
• WHO TRS Guidelines on Pharmaceutical Development

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Tanvi Mehra	Rakesh Pawar	Sunita Reddy
Designation	Formulation Analyst	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: Stability Observation Log

Date	Condition	Phase Separation	Creaming	Color Change	Status
21/05/2025	40°C / 75% RH	None	None	No change	Pass

Annexure-2: pH and Viscosity Measurement Log

Date	pH	Viscosity (cP)	Status
21/05/2025	5.8	4600	Pass

Annexure-3: Validation Summary Report

Method validated across three emulsion types. Droplet size RSD = 2.4%, pH variation within ±0.3 units, viscosity within ±10%. The method is robust under temperature and light stress. Suitable for ongoing formulation stability programs.

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Added freeze-thaw cycle study and zeta potential option	Annual Review	Sunita Reddy
10/04/2022	1.0	Initial SOP Release	New SOP	QA Head