in pharmaceutical laboratories. The procedure ensures accurate, sensitive, and reliable quantification of organic analytes.

2. Scope

This SOP applies to the Analytical Method Development (AMD) laboratory and is applicable for all gas chromatographic methods employing FID to analyze volatile and semi-volatile organic compounds in raw materials, intermediates, and finished drug products.

3. Responsibilities

• Analytical Chemist: Responsible for FID setup, ignition, calibration, and routine performance checks.
• Method Reviewer: Validates detector linearity and response consistency for target analytes.
• QA Officer: Ensures documentation and safety protocols are maintained as per GLP/GMP guidelines.
• Head – AMD: Approves SOP implementation and updates based on regulatory or technical changes.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring proper operation, calibration, and validation of FID-based GC methods in accordance with regulatory requirements.

5. Procedure

5.1 Principle of FID

1. FID detects ions formed during combustion of organic compounds in a hydrogen-air flame.
2. The detector generates a current proportional to the number of carbon atoms, enabling sensitive detection of hydrocarbons and other volatile organics.
3. Compounds lacking C-H bonds (e.g., H₂O, CO₂, NO_x) are not detected.

5.2 Installation and Configuration

1. Ensure correct gas connections:
   • Hydrogen: 30–40 mL/min
   • Air: 300–400 mL/min
   • Make-up Gas (typically Nitrogen): 20–30 mL/min
2. Set detector temperature to 250–300°C.
3. Ensure column effluent is aligned directly into FID nozzle.
4. Document setup in Annexure-1: FID Configuration Checklist.

5.3 Ignition of Flame

1. Ensure proper carrier and detector gas flow is established.
2. Activate air and hydrogen flow via GC control panel.
3. Ignite flame either automatically (via GC ignition button) or manually using ignitor.
4. Visually confirm steady flame or monitor via baseline current (~10–20 pA).
5. If flame extinguishes, troubleshoot gas flow, leaks, or contamination.

5.4 Baseline Stabilization and Blank Check

1. Allow flame to stabilize for 15–30 minutes.
2. Inject blank solvent and ensure baseline noise is minimal and no ghost peaks are present.
3. Document baseline reading and blank response in Annexure-2: Baseline Stability Log.

5.5 Calibration and Linearity

1. Inject standard solutions at 5 concentration levels (50%, 80%, 100%, 120%, 150%).
2. Plot peak area versus concentration.
3. Acceptance criteria:
   • R² ≥ 0.995
   • %RSD ≤ 2% at 100% level
4. Document in Annexure-3: FID Calibration Report.

5.6 Sensitivity and Detection Limit

1. Determine signal-to-noise (S/N) ratio for low-level standard.
2. Acceptance:
   • LOD: S/N ≥ 3
   • LOQ: S/N ≥ 10
3. Record results in Annexure-4: Detection Limit Report.

5.7 Routine Performance Verification

1. Inject known standard once daily to verify:
   • Retention time stability (±0.1 min)
   • Peak response deviation (≤ 5%)
2. Document results in Annexure-5: Daily Performance Log.

5.8 Maintenance of FID

1. Daily: Wipe nozzle area, ensure gas lines are free of leaks.
2. Weekly: Clean jet or replace septa and liner.
3. Monthly: Check H₂, air, and N₂ purity and flow regulators.
4. Log activities in Annexure-6: FID Maintenance Log.

5.9 Safety Precautions

1. Never ignite flame if hydrogen is flowing without air — risk of explosion.
2. Use leak detection fluid to ensure gas fittings are tight and leak-free.
3. Wear PPE and ensure good ventilation when using hydrogen gas.
4. In case of flame-out, purge system for 5 minutes before re-igniting.

6. Abbreviations

• FID: Flame Ionization Detector
• GC: Gas Chromatography
• LOD: Limit of Detection
• LOQ: Limit of Quantification
• RSD: Relative Standard Deviation
• SOP: Standard Operating Procedure

7. Documents

1. FID Configuration Checklist – Annexure-1
2. Baseline Stability Log – Annexure-2
3. FID Calibration Report – Annexure-3
4. Detection Limit Report – Annexure-4
5. Daily Performance Log – Annexure-5
6. FID Maintenance Log – Annexure-6

8. References

• ICH Q2(R1) – Validation of Analytical Procedures
• USP <621> – Chromatography
• Manufacturer Manuals – Agilent, Shimadzu, Thermo GC Systems
• GMP and EHS Guidelines – Gas Handling Safety

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: FID Configuration Checklist

Parameter	Setting	Verified By
Hydrogen Flow	35 mL/min	Sunita Reddy
Air Flow	350 mL/min	Sunita Reddy
Detector Temp	280°C	Rajesh Kumar

Annexure-2: Baseline Stability Log

Date	Current (pA)	Noise	Observation
19/05/2025	14.5	Stable	Acceptable

Annexure-3: FID Calibration Report

Level (%)	Concentration (ppm)	Area	Status
100	1000	105623	Pass

Annexure-4: Detection Limit Report

Standard (ppm)	S/N Ratio	LOD	LOQ
10	35	3 ppm	10 ppm

Annexure-5: Daily Performance Log

Date	Sample	RT (min)	Area	Status
19/05/2025	STD-101	6.25	105623	Complies

Annexure-6: FID Maintenance Log

Date	Activity	Performed By	Remarks
17/05/2025	Nozzle cleaning	Rajesh Kumar	Flame stable

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Integrated detector calibration and safety annexures	Annual SOP Review