Elixir Department: SOP for Viscosity Testing During Mixing – V 2.0

Standard Operating Procedure for Viscosity Testing During Mixing in Elixir Manufacturing

Department	Elixir Department
SOP No.	SOP/ELX/193/2025
Supersedes	SOP/ELX/193/2022
Page No.	Page 1 of 9
Issue Date	11/04/2025
Effective Date	15/04/2025
Review Date	11/04/2026

1. Purpose

To establish a consistent procedure for monitoring and recording viscosity during the mixing process in elixir manufacturing to ensure batch-to-batch consistency and product quality.

2. Scope

This SOP applies to all elixir formulations where viscosity is a critical quality attribute (CQA) and must be monitored in real-time or at predefined mixing intervals within the Elixir Manufacturing Department.

3. Responsibilities

Production Operator:
- Conduct viscosity testing using the designated viscometer at defined stages of mixing.
- Document viscosity values in the logbook.
QC Analyst:
- Verify and re-test critical viscosity readings when required.
QA Officer:
- Ensure that viscosity measurements are performed and recorded in compliance with SOP.

4. Accountability

The Production Head is accountable for ensuring that viscosity testing is performed at specified intervals. The QA Head ensures GMP compliance and documentation review.

5. Procedure

5.1

Equipment and Preparation

Use a calibrated rotational viscometer (e.g., Brookfield Viscometer) suitable for liquid formulations.
Ensure spindle selection is appropriate for expected viscosity range.
Verify calibration using standard viscosity reference fluid before use.
Record calibration in the Equipment Calibration Logbook.

5.2 Sampling for Viscosity

Collect 100 mL of elixir from the mixing tank using a clean sampling beaker.
Ensure the sample is free from air bubbles and taken after homogenized mixing.
Record the temperature of the sample before testing.

5.3 Viscosity Measurement

Immerse the spindle fully in the sample as per instrument guidelines.
Select the correct RPM and spindle based on the validation protocol.
Allow reading to stabilize for 30–60 seconds before recording the value in centipoise (cP).
Measure viscosity at predefined time points:
- After 50% mixing time
- At end of mixing
- Just before cooling or filtration

5.4 Acceptance Criteria and Actions

Compare recorded values with the product specification range defined in the BMR.
If out-of-specification (OOS), notify QA and hold the batch.
Investigate possible causes (e.g., incomplete dissolution, incorrect ingredient quantity).

5.5 Cleaning and Maintenance

Clean spindle with purified water or appropriate solvent immediately after use.
Dry and store as per equipment SOP.

5.6 Documentation

Record viscosity results in the Viscosity Monitoring Logbook (Annexure-1).
Include Batch No., Sample Time, Temperature, Spindle No., RPM, and Observed Viscosity.
QA shall verify log entries and sign off.

6. Abbreviations

SOP: Standard Operating Procedure
QA: Quality Assurance
QC: Quality Control
RPM: Revolutions Per Minute
cP: Centipoise

7. Documents

Viscosity Monitoring Logbook (Annexure-1)
BMR Reference Sheet
Viscometer Calibration Log

8. References

ICH Q8 – Pharmaceutical Development
21 CFR Part 211.110 – Sampling and Testing of In-Process Materials
WHO TRS 986 – GMP Guidelines

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Viscosity Monitoring Logbook

Date	Batch No.	Time Point	Spindle/RPM	Observed Viscosity (cP)	Temperature (°C)	Operator	QA Verified
11/04/2025	ELX-0425-012	Post-Mixing	S62 / 60	120 cP	27.5	Rajesh Kumar	Sunita Reddy

Revision History:

Revision Date	Revision No.	Revision Details	Reason for Revision	Approved By
01/01/2024	1.0	Initial Release	New SOP	QA Head
11/04/2025	2.0	Added specific sampling stages and QC retest clause	Process Improvement	QA Head