and compliance with product specifications.

2. Scope

This SOP is applicable to the Analytical Method Development and Quality Control departments performing visual or instrumental analysis of color variation across coated tablets during development, manufacturing, and stability testing.

3. Responsibilities

• Analytical Scientist: Develops and standardizes the procedure for color uniformity assessment.
• QC Analyst: Conducts routine testing using visual and/or instrumental techniques.
• QA Executive: Reviews documentation and ensures compliance with appearance specifications.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring consistent methodology and color acceptance criteria, in line with regulatory and internal standards.

5. Procedure

5.1 Sample Preparation

1. Collect 30 coated tablets randomly from the batch (representing all layers of the container).
2. Wipe gently with lint-free cloth to remove surface dust if needed.
3. Do not expose to bright light or moisture prior to analysis.

5.2 Visual Inspection (Preliminary)

1. Arrange tablets on a clean white background under standardized lighting (e.g., D65 daylight simulator).
2. Observe for any visible color variation, spots, streaks, or non-uniform coating.
3. Record observations against predefined categories (e.g., acceptable, slight variation, reject).

5.3 Instrumental Color Measurement

1. Use a calibrated colorimeter or spectrophotometer in reflectance mode.
2. Set color space as CIE L*a*b* or HunterLab as per internal specification.
3. Measure L*, a*, b* values for each tablet at three different orientations (top, bottom, side).
4. Calculate average and standard deviation for all 30 units.

5.4 Acceptance Criteria

• No tablet should show significant visual defects like discoloration, non-uniform coating, or chipping.
• Colorimeter:
  • ∆E (total color difference) between tablets ≤ 1.5 (acceptable)
  • Standard deviation of L*, a*, b* values ≤ 1.0

5.5 Validation Parameters

1. Repeatability: Perform three replicates on same tablet set, RSD ≤ 2%
2. Instrument Calibration: Confirm with standard white and color tiles before use
3. Robustness: Evaluate at different lighting temperatures (D65, TL84, CWF)

6. Abbreviations

• ∆E: Total color difference
• CIE: Commission Internationale de l’Éclairage
• L*: Lightness
• a*: Red-green axis
• b*: Yellow-blue axis

7. Documents

1. Tablet Color Uniformity Log – Annexure-1
2. Colorimeter Output Summary – Annexure-2
3. Visual Inspection Checklist – Annexure-3

8. References

• USP <1061>: Color Uniformity of Dosage Forms
• ICH Q6A: Specifications – Test Procedures and Acceptance Criteria
• CIE Publication No. 15: Colorimetry (3rd Edition)

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Vinita Joshi	Pradeep Malhotra	Sunita Reddy
Designation	Analytical Chemist	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: Tablet Color Uniformity Log

Tablet ID	L*	a*	b*	∆E	Status
CU-288-01	72.1	4.5	18.2	1.2	Pass

Annexure-2: Colorimeter Output Summary

Standard deviation of L* = 0.8, a* = 0.6, b* = 0.5; ∆E between units within acceptable range. No outliers observed.

Annexure-3: Visual Inspection Checklist

Observation	Count	Remarks
No Defects	28	Uniform appearance
Slight Variation	2	Acceptable under threshold
Rejects	0	None observed

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Integrated ∆E analysis and CIE L*a*b* parameters	Annual SOP Review	Sunita Reddy
15/11/2022	1.0	Initial SOP Release	New SOP	QA Head