analyzers. It applies to analysis of water samples, cleaning validation swabs, rinse samples, and other low-carbon pharmaceutical matrices.

2. Scope

This SOP is applicable to the Analytical Method Development (AMD) department for TOC method development using combustion or UV-persulfate oxidation-based analyzers for pharmaceutical water systems, cleaning validation, and process monitoring, in accordance with USP <643>, EP 2.2.44, and ICH Q2(R1).

3. Responsibilities

• Analytical Scientist: Prepares calibration and sample solutions, operates the TOC analyzer, and documents results.
• Reviewer: Verifies raw data, calibration curves, and validation reports for accuracy and compliance.
• QA Officer: Ensures documentation adherence to GMP, USP, and ICH guidelines.
• Head – AMD: Approves validated methods for use in routine analysis or cleaning validation programs.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring that TOC methods are properly developed, validated, and documented in compliance with applicable regulatory requirements.

5. Procedure

5.1 Principle of TOC Analysis

1. TOC analysis involves measuring the carbon content of organic compounds in aqueous solutions by converting them to CO₂ and detecting the carbon dioxide using:
   • Non-dispersive infrared (NDIR) detection (for combustion analyzers)
   • Conductivity detection (for UV-persulfate oxidizers)
2. The result is expressed in ppm or ppb of carbon (mg/L or µg/L).

5.2 Instrument and Calibration Setup

1. Switch ON the TOC analyzer and allow system warm-up (30–60 minutes).
2. Perform auto-calibration using standard solutions:
   • 0 ppm (blank)
   • 1 ppm
   • 5 ppm
   • 10 ppm
3. Use potassium hydrogen phthalate (KHP) or sucrose as calibration standards.
4. Ensure R² ≥ 0.999 for linearity across calibration curve.
5. Document all calibration results in Annexure-1: TOC Calibration Log.

5.3 Sample Preparation and Handling

1. Use only TOC-grade water, glassware, and swabs.
2. Ensure no carbon contamination from sample containers or atmospheric exposure.
3. Swab samples (for cleaning validation):
   • Use pre-rinsed low-carbon swabs
   • Extract swab into 10 mL TOC water for 30 minutes
4. Rinse samples:
   • Collect 100–200 mL final rinse water from equipment surface
5. Store samples at 2–8°C and analyze within 24 hours.
6. Document in Annexure-2: Sample Log Sheet.

5.4 System Suitability and Blank Check

1. Before sample analysis, inject blank (TOC water) to confirm background < 50 ppb.
2. Inject mid-level standard (5 ppm) three times:
   • % RSD of response should be ≤ 2.0%
3. Perform system suitability check daily before sample testing.
4. Document results in Annexure-3: System Suitability Record.

5.5 Method Optimization

1. Evaluate:
   • Combustion vs. UV-persulfate oxidation efficiency
   • Sample volume (typically 30–50 µL)
   • Inlet rinse cycles to reduce memory effects
   • Interference from inorganic carbon (IC) and proper IC removal method (acidification and purging)
2. Optimize number of replicate injections (min. 3) and auto-sampler rinse cycles.
3. Record optimization trials in Annexure-4: Method Optimization Log.

5.6 Method Validation

1. Linearity: 0.1 to 10 ppm range; R² ≥ 0.999
2. Accuracy: Spike recovery between 95%–105%
3. Precision:
   • Repeatability: RSD ≤ 2.0% for 6 replicates
   • Intermediate Precision: Two analysts/days
4. LOD & LOQ: Determine based on standard deviation of low-level replicates
5. Specificity: Confirm negligible interference from matrix or excipients
6. Robustness: Vary purge time, sample volume, and IC removal parameters
7. Document in Annexure-5: Validation Summary Report.

5.7 Final Method Documentation

1. Compile finalized method including:
   • System settings and oxidation mode
   • Calibration range and standard prep
   • Sample prep guidelines for different matrices
   • Acceptable criteria for cleaning validation
   • System suitability and troubleshooting
2. Submit final method to QA for review and approval.

6. Abbreviations

• TOC: Total Organic Carbon
• KHP: Potassium Hydrogen Phthalate
• RSD: Relative Standard Deviation
• LOD: Limit of Detection
• LOQ: Limit of Quantification
• NDIR: Non-Dispersive Infrared

7. Documents

1. TOC Calibration Log – Annexure-1
2. Sample Log Sheet – Annexure-2
3. System Suitability Record – Annexure-3
4. Method Optimization Log – Annexure-4
5. Validation Summary Report – Annexure-5

8. References

• USP <643> – Total Organic Carbon
• EP 2.2.44 – TOC in Pharmaceutical Waters
• ICH Q2(R1) – Validation of Analytical Procedures
• FDA Cleaning Validation Guidance (2021)

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: TOC Calibration Log

Standard (ppm)	Response	Average	R²
0.0, 1.0, 5.0, 10.0	Auto-injected	Valid	0.9997

Annexure-2: Sample Log Sheet

Sample Type	ID	Volume (mL)	Storage Temp	Analyzed By
Rinse Water	TOC-RW-102	100	2–8°C	Sunita Reddy

Annexure-3: System Suitability Record

Injection	TOC (ppm)
1	5.01
2	4.98
3	5.02

Annexure-4: Method Optimization Log

Trial	Parameter	Setting	Observation	Conclusion
1	Purging Time	6 min	IC effectively removed	Accepted

Annexure-5: Validation Summary Report

Parameter	Criteria	Result	Status
Accuracy	95–105%	98.7%	Pass
Precision	RSD ≤ 2%	1.1%	Pass
LOD	Estimated	0.02 ppm	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Integrated swab and rinse procedures with expanded validation scope	Annual SOP Review