compounds during method development.

2. Scope

This SOP is applicable to all GC method development and validation activities conducted in the Analytical Method Development (AMD) department involving pharmaceutical raw materials, intermediates, or drug products requiring chemical modification prior to analysis.

3. Responsibilities

• Analytical Chemist: Performs derivatization, method development, and documentation of GC parameters.
• Reviewer: Validates method optimization and evaluates specificity and repeatability.
• QA Officer: Ensures compliance with safety, reagent handling, and recordkeeping.
• Head – AMD: Approves the finalized method for analytical and regulatory use.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring derivatization methods are appropriate, justified, and validated as per ICH and compendial guidelines.

5. Procedure

5.1 Introduction to Derivatization

1. Derivatization involves chemical modification of analytes to improve:
   • Volatility
   • Thermal stability
   • Detector response (especially for FID or MS)
2. Common functional groups targeted: hydroxyl, amine, carboxylic acid, carbonyl.
3. Document compound functional groups in Annexure-1: Functional Group Mapping Sheet.

5.2 Selection of Derivatization Reagents

1. Choose reagent based on analyte functional group:
   • Silylation: BSTFA, MSTFA for OH, COOH, NH₂
   • Acylation: Acetic anhydride, PFPA for hydroxyl or amino groups
   • Alkylation: Diazomethane, iodomethane for COOH groups
2. Ensure reagent compatibility with matrix and GC column.
3. Record justification in Annexure-2: Reagent Selection Log.

5.3 Derivatization Procedure

1. Silylation (e.g., using BSTFA):
   • Weigh 2–10 mg sample in reaction vial.
   • Add 100–200 µL BSTFA + 1% TMCS reagent.
   • Incubate at 60°C for 30 minutes in dry conditions.
2. Acylation (e.g., with acetic anhydride):
   • Dissolve sample in pyridine.
   • Add equal volume of acetic anhydride and vortex.
   • Incubate at room temperature for 15–30 min.
3. Alkylation (e.g., using diazomethane):
   • Use freshly prepared diazomethane in ethereal solution.
   • Add dropwise to sample in dried solvent (e.g., methanol).
   • React under fume hood for 10–20 min at RT.
4. Filter and inject derivatized sample immediately.
5. Log experimental conditions in Annexure-3: Derivatization Execution Log.

5.4 GC Method Development

1. Select non-polar columns (e.g., DB-1, DB-5) for derivatized compounds.
2. Optimize oven temperature ramp to prevent early elution or degradation.
3. Validate injection port compatibility (split vs splitless).
4. Run blank and derivatized sample for comparison.
5. Document in Annexure-4: GC Method Development Worksheet.

5.5 Specificity and Linearity

1. Ensure no interference from unreacted reagent or by-products.
2. Run linearity with derivatized standards over 5 concentration levels.
3. Acceptance Criteria:
   • R² ≥ 0.995
   • %RSD ≤ 2%
4. Log data in Annexure-5: Linearity and Specificity Report.

5.6 Safety and Waste Disposal

1. Use derivatizing agents in fume hood with appropriate PPE (gloves, goggles, lab coat).
2. Label all reagents and derivatized vials with hazard warnings.
3. Dispose of excess reagents and derivatized waste as per EHS guidelines.
4. Record in Annexure-6: Reagent Safety and Disposal Log.

6. Abbreviations

• GC: Gas Chromatography
• BSTFA: N,O-Bis(trimethylsilyl)trifluoroacetamide
• MSTFA: N-Methyl-N-(trimethylsilyl)trifluoroacetamide
• FID: Flame Ionization Detector
• SOP: Standard Operating Procedure

7. Documents

1. Functional Group Mapping Sheet – Annexure-1
2. Reagent Selection Log – Annexure-2
3. Derivatization Execution Log – Annexure-3
4. GC Method Development Worksheet – Annexure-4
5. Linearity and Specificity Report – Annexure-5
6. Reagent Safety and Disposal Log – Annexure-6

8. References

• ICH Q2(R1) – Validation of Analytical Procedures
• USP <621> – Chromatography
• USP General Chapter on Derivatization Techniques (if applicable)
• Regulatory EHS Guidelines – Chemical Handling and Disposal

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Functional Group Mapping Sheet

Sample ID	Functional Group	Reactivity
API-101	Carboxylic acid	Requires methylation

Annexure-2: Reagent Selection Log

Analyte	Reagent	Derivatization Type	Justification
API-101	BSTFA	Silylation	Improves volatility and detection

Annexure-3: Derivatization Execution Log

Date	Sample ID	Reagent	Incubation Temp	Time	Remarks
18/05/2025	API-101	BSTFA	60°C	30 min	Clear solution

Annexure-4: GC Method Development Worksheet

Column	Oven Program	Injection Mode	Split Ratio
DB-5	50–280°C @ 10°C/min	Split	10:1

Annexure-5: Linearity and Specificity Report

Level (%)	Peak Area	% RSD	Status
100%	124523	1.2%	Pass

Annexure-6: Reagent Safety and Disposal Log

Reagent	Hazard Class	PPE Used	Disposal Method
BSTFA	Flammable, corrosive	Gloves, goggles	Organic solvent waste bin

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Annexures for safety and specificity added	Regulatory and EHS alignment