matter) present in pharmaceutical substances and excipients using Residue on Ignition (ROI) or Sulphated Ash techniques. The goal is to ensure accuracy, reproducibility, and regulatory compliance.

2. Scope

This SOP applies to the development and validation of methods for ROI/Sulphated Ash determination in drug substances, raw materials, excipients, and formulations in the AMD laboratory using muffle furnaces and sulphuric acid treatments as per compendial standards.

3. Responsibilities

• Analytical Chemist: Carries out method development and performs ignition procedures.
• Reviewer: Verifies weight recordings, furnacing cycles, and calculations.
• QA: Reviews validation records and ensures compliance with USP/IP/Ph. Eur. specifications.
• Head – AMD: Approves the final method and oversees adherence to regulatory protocols.

4. Accountability

The Head of AMD is accountable for ensuring that the ROI/Sulphated Ash method is developed, validated, and implemented in accordance with GMP and pharmacopeial guidelines.

5. Procedure

5.1 Method Selection

1. Choose between:
   • Residue on Ignition (ROI): Dry ashing without sulphuric acid (used for organic compounds).
   • Sulphated Ash: Uses concentrated sulphuric acid for complete oxidation and destruction of organic matter.
2. Refer to USP <281>, IP, or Ph. Eur. guidelines to identify appropriate method.
3. Record the selected approach in Annexure-1: Method Development Strategy Sheet.

5.2 Equipment Qualification

1. Ensure muffle furnace is:
   • Calibrated and qualified (temp accuracy ±10°C)
   • Fitted with a certified reference thermometer or data logger
2. Verify analytical balance calibration and log the verification in lab records.

5.3 Sample Preparation

1. Weigh 1–2 g of test sample accurately into a pre-ignited and tarred crucible.
2. Record weight in Annexure-2: Sample Weight and ROI Log.
3. For sulphated ash, moisten the sample with concentrated sulphuric acid (~1 mL) prior to ignition.

5.4 Ignition Procedure

1. Place the crucible in a cool muffle furnace.
2. Gradually raise temperature to 600 ± 25°C over 30 minutes to avoid splattering.
3. Maintain the temperature for 2 hours or until white/grey ash is obtained.
4. Cool the crucible in a desiccator for 30 minutes and weigh.
5. Repeat ignition if carbon residue is still visible.

5.5 Calculation

Residue (%) = [(Weight of residue) / (Initial sample weight)] × 100

1. Perform triplicate trials and calculate mean and RSD.
2. Record data in Annexure-3: ROI/Sulphated Ash Calculation Sheet.

5.6 Method Optimization

1. Evaluate:
   • Effect of drying temperature (e.g., 550°C vs 600°C)
   • Sample size and crucible type
   • Sulphuric acid pre-treatment efficacy
2. Document all optimization trials in Annexure-4: Method Optimization Log.

5.7 Method Validation

1. Validate using ICH Q2(R1) guidance:
2. Precision: Triplicate analysis on same and different days; RSD ≤ 2.0%.
3. Accuracy: Spike known inorganic residue and recover within 98–102%.
4. Specificity: Show that ash originates from inorganic material.
5. Robustness: Assess minor variation in temperature and ashing duration.
6. Compile validation in Annexure-5: Validation Summary Report.

6. Abbreviations

• ROI: Residue on Ignition
• AMD: Analytical Method Development
• RSD: Relative Standard Deviation
• GMP: Good Manufacturing Practices
• QA: Quality Assurance

7. Documents

1. Method Development Strategy Sheet – Annexure-1
2. Sample Weight and ROI Log – Annexure-2
3. ROI/Sulphated Ash Calculation Sheet – Annexure-3
4. Method Optimization Log – Annexure-4
5. Validation Summary Report – Annexure-5

8. References

• USP <281> – Residue on Ignition
• IP 2022 – Sulphated Ash
• Ph. Eur. – 2.4.14 Sulphated Ash
• ICH Q2(R1) – Validation of Analytical Procedures
• 21 CFR Part 211 – Laboratory Controls

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Method Development Strategy Sheet

Sample	Method Type	Pre-treatment	Remarks	Prepared By
Excipent-A	Sulphated Ash	H2SO4	Sticky material, requires acid digestion	Ajay Verma

Annexure-2: Sample Weight and ROI Log

Date	Sample	Crucible No.	Initial Wt (g)	Residue Wt (g)	Residue (%)
03/05/2025	API-X	001	1.005	0.012	1.19

Annexure-3: ROI/Sulphated Ash Calculation Sheet

Trial	Initial Weight (g)	Residue Weight (g)	ROI (%)	Analyst
1	1.005	0.012	1.19	Sunita Reddy

Annexure-4: Method Optimization Log

Parameter	Condition	Result	Conclusion
Temp	550°C	Residue = 1.40%	Incomplete combustion
Temp	600°C	Residue = 1.19%	Complete ashing

Annexure-5: Validation Summary Report

Parameter	Acceptance Criteria	Results	Status
Precision	RSD ≤ 2%	1.4%	Pass
Accuracy	98–102%	99.1%	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Added optimization criteria and acid pre-treatment clarification	Regulatory Inspection Readiness