in injectable pharmaceutical products using light obscuration and microscopic techniques.

2. Scope

This SOP is applicable to Analytical Method Development and Quality Control departments involved in the establishment and validation of subvisible particulate matter testing for aqueous and non-aqueous parenteral drug products.

3. Responsibilities

• Analytical Scientist: Develops and validates the method for subvisible particulate matter testing.
• QC Analyst: Performs routine testing of injectable batches using approved methods.
• QA Executive: Ensures test compliance with pharmacopoeial standards and reviews reports.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring that the developed method meets USP <788>, Ph. Eur. 2.9.19, and other applicable regulatory standards.

5. Procedure

5.1 Instrument Selection

1. Use Light Obscuration Particle Counter as the primary method for aqueous injectables.
2. Use Microscopic Particle Count method as alternate or confirmatory method for oil-based or viscous injectables.

5.2 Sample Preparation

1. Collect test samples in clean glass containers under aseptic and particulate-free conditions.
2. Degas and equilibrate samples to room temperature (20–25°C).
3. Filter air and clean equipment before operation to minimize false readings.

5.3 Test Procedure (Light Obscuration)

1. Perform calibration and verification of the instrument using certified polystyrene bead standards.
2. Rinse sensor with WFI before and after each run.
3. Inject at least three 5 mL aliquots of test solution; discard the first and average the next two.
4. Record cumulative counts of ≥10 µm and ≥25 µm particles per mL.

5.4 Test Procedure (Microscopic Count)

1. Filter 25 mL of sample through 0.8 µm membrane filter.
2. Rinse filter with WFI and mount on microscope slide.
3. Scan 10 fields under 100x magnification and record count of ≥10 µm and ≥25 µm particles.

5.5 Acceptance Criteria (USP <788>)

• For small volume injections (<100 mL):
  • NMT 6000 particles ≥10 µm per container
  • NMT 600 particles ≥25 µm per container
• For large volume injections (≥100 mL):
  • NMT 25 particles/mL ≥10 µm
  • NMT 3 particles/mL ≥25 µm

5.6 Method Validation

1. Precision: RSD ≤ 10% for replicate counts.
2. Accuracy: Recovery of certified standards within ±10%.
3. Specificity: Method should detect particles and distinguish from bubbles or dust.
4. Linearity: Demonstrated by diluting a known particle suspension.
5. Ruggedness: Perform testing with different analysts and instruments.

6. Abbreviations

• RSD: Relative Standard Deviation
• WFI: Water for Injection
• USP: United States Pharmacopeia
• Ph. Eur.: European Pharmacopoeia
• QA: Quality Assurance

7. Documents

1. Particulate Matter Test Log – Annexure-1
2. Calibration Certificate for Particle Counter – Annexure-2
3. Method Validation Report – Annexure-3

8. References

• USP <788>: Particulate Matter in Injections
• Ph. Eur. 2.9.19: Particulate Contamination
• ICH Q2(R1): Validation of Analytical Procedures

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Rakesh Pawar	Vaishali Gupta	Sunita Reddy
Designation	Particle Testing Chemist	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: Particulate Matter Test Log

Sample ID	≥10 µm (particles/mL)	≥25 µm (particles/mL)	Status
PMT-278-01	12	1	Pass

Annexure-2: Calibration Certificate

Calibration performed on 15/05/2025 using 10 µm and 25 µm NIST-traceable bead standards. Instrument performance was within limits.

Annexure-3: Method Validation Report

The developed method for subvisible particulate matter quantification was validated as per USP and ICH guidelines. Results demonstrated accuracy, precision, and ruggedness. Method deemed suitable for QC and stability testing.

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Integrated microscopic method and updated validation strategy	Annual Review	Sunita Reddy
10/04/2022	1.0	Initial SOP Release	New SOP	QA Head