to all injectable formulations manufactured at the facility that require osmolality testing as part of routine batch release, stability studies, or development trials.

3. Responsibilities

• QC Analyst: Conduct osmolality tests and document the data.
• QC Reviewer: Review raw data and compiled results for accuracy.
• Instrument Technician: Calibrate and maintain the osmometer as per schedule.
• QA Department: Review and approve final osmolality results.

4. Accountability

The Head of Quality Control is accountable for ensuring compliance with this SOP and for maintaining instrument readiness and data integrity.

5. Procedure

5.1 Principle

Osmolality is a measure of the osmotic concentration of a solution and is expressed in milliosmoles per kilogram of water (mOsm/kg H₂O). The osmometer operates on the freezing point depression method, where the degree to which freezing point is lowered corresponds to the concentration of solute particles.

5.2 Equipment and Materials

• Freezing point depression osmometer (e.g., Advanced Instruments Model 3250)
• Micropipette with disposable tips
• Calibrated thermometers
• Calibration standards (100 mOsm/kg, 290 mOsm/kg, and 1000 mOsm/kg)
• Deionized water
• QC test sample
• Log book or LIMS system

5.3 Calibration and Verification

1. Calibrate the osmometer using certified osmolality standards before use.
2. Document the calibration values in the calibration log (Annexure-1).
3. Perform daily verification with 290 mOsm/kg control standard and record acceptance (±2% of label claim).

5.4 Sample Preparation

1. Ensure the sample vial is labeled and traceable to the batch number.
2. Equilibrate sample to room temperature (20–25°C).
3. Mix the sample gently without introducing air bubbles.

5.5 Osmolality Measurement

1. Turn on the osmometer and allow it to initialize.
2. Use a micropipette to draw 50 μL of sample.
3. Inject the sample into the sample port of the osmometer.
4. Start the measurement cycle and allow instrument to complete freezing point depression analysis.
5. Note the displayed osmolality reading (mOsm/kg) and document in test worksheet (Annexure-2).
6. Repeat the analysis in duplicate to confirm reproducibility (±3 mOsm/kg).

5.6 Acceptance Criteria

• Osmolality of isotonic injectable products must fall within 270–310 mOsm/kg unless otherwise specified.
• For hypertonic or hypotonic formulations, acceptance criteria should be defined in the product specification.
• Difference between duplicate readings should not exceed 3 mOsm/kg.

5.7 Cleaning and Shutdown

1. After use, flush the sample port with deionized water.
2. Wipe external surfaces with lint-free cloth.
3. Shut down the instrument and enter activity in instrument usage log.

5.8 Documentation

1. All readings, observations, and calculations must be recorded in Annexure-2.
2. Report deviations or out-of-specification results to QA using deviation form.
3. Maintain raw data and logbooks for a minimum of 5 years or as per regulatory requirements.

6. Abbreviations

• SOP: Standard Operating Procedure
• QC: Quality Control
• QA: Quality Assurance
• LIMS: Laboratory Information Management System
• mOsm/kg: Milliosmoles per kilogram of water

7. Documents

1. Calibration Log – Annexure-1
2. Osmolality Test Worksheet – Annexure-2
3. Instrument Usage Log – Annexure-3

8. References

• USP <791> – Osmolality and Osmolarity
• ICH Q2(R1) – Validation of Analytical Procedures
• 21 CFR Part 211 – CGMP for Finished Pharmaceuticals

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation	QC Analyst	QA Executive	Head QA
Department	Quality Control	Quality Assurance	Quality Assurance

11. Annexures

Annexure-1: Calibration Log

Date	Standard Used	Expected Value	Observed Value	Performed By
24/06/2025	290 mOsm/kg	290	291	Arun Pillai

Annexure-2: Osmolality Test Worksheet

Sample ID	Batch No.	Test 1	Test 2	Average	Status	Analyst
INJ001	B230615	289	288	288.5	Pass	Meena Iyer

Annexure-3: Instrument Usage Log

Date	Time	User	Purpose	Remarks
24/06/2025	10:00 AM	Meena Iyer	Batch Release	Normal Operation

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
01/02/2022	1.0	Initial Version	New SOP	QA Head
24/06/2025	2.0	Added duplicate testing and annexures	Annual Review	QA Head