1.0 Objective:
To describe the procedure for analyzing and identifying gases formed in the blister cavities of Amoxicillin and Potassium Clavulanate tablets using Gas Chromatography (GC).
2.0 Scope:
This SOP applies to the analysis of gases collected from bulged or swollen blister packs suspected to contain trapped gases due to degradation or leakage.
3.0 Responsibility:
- QC Analyst: Perform the test and record results.
- QC Reviewer: Verify chromatograms and calculations.
- QA Officer: Review and approve the final report.
4.0 References:
- USP–NF: Amoxicillin and Potassium Clavulanate Tablets
- ICH Q1A (R2): Stability Testing of New Drug Products
- ASTM F1929: Packaging Integrity Test Methods
5.0 Apparatus & Materials:
- Gas Chromatograph with Thermal Conductivity Detector (TCD)
- Columns: Molecular Sieve 5A and/or Porapak Q
- Gas-tight syringe (250–500 µL, Hamilton type)
- Helium (carrier gas, high purity)
- Certified gas standards (CO₂, O₂, N₂)
- Crimp vials (10–20 mL) with butyl/PTFE septa
- Micro-needle and piercing assembly
- Isopropyl alcohol wipes
6.0 Procedure:
6.1 Sample Collection:
- Select representative bulged blister packs.
- Clean surface with isopropyl alcohol and allow to dry.
- Insert a fine needle through the bulged cavity without damaging the tablet.
- Using a gas-tight syringe, withdraw 200–500 µL of headspace gas.
- Immediately inject into GC or transfer into a sealed GC vial for short-term storage (<30 min).
6.2 Instrument Setup:
| Parameter | Setting |
|---|---|
| Detector | TCD |
| Carrier Gas | Helium or Nitrogen, 20–30 mL/min |
| Column | Molsieve 5A / Porapak Q |
| Injector Temp | 100–150 °C |
| Oven Temp | 40–60 °C (isothermal) |
| Detector Temp | 150–200 °C |
| Injection Mode | Splitless |
6.3 Calibration:
- Inject standard gas mixtures (low, medium, high) containing CO₂, O₂, N₂.
- Plot calibration curves for each gas (Area vs % concentration).
- Verify correlation coefficient (R² ≥ 0.995).
- Run a mid-level calibration verification after every 10 samples.
6.4 Sample Injection:
- Purge syringe once with sample gas before final draw.
- Inject 100–500 µL of sample directly into the GC inlet.
- Record chromatogram and note retention times for CO₂, O₂, N₂.
6.5 Calculations:
- Determine gas concentration using the external calibration curve.
- For air ingress:
- Expected ratio: N₂:O₂ ≈ 79:21.
- Excess CO₂ indicates possible chemical degradation (clavulanate hydrolysis).
- Report values in % v/v or ppm.
6.6 Acceptance Criteria:
| Parameter | Expected Range | Interpretation |
|---|---|---|
| CO₂ | ≤0.04% | Normal (ambient) |
| CO₂ >0.5% | Product degradation / moisture ingress | |
| O₂:N₂ ratio ≈ 21:79 | Air ingress (seal failure) | |
| Other gases (H₂, CH₄, etc.) | Not detected | Contamination if present |
7.0 Quality Control:
- Run blank and standard before and after each batch.
- Duplicate injection RPD ≤ 10%.
- Maintain all chromatograms and raw data with sample ID and date.
8.0 Precautions:
- Avoid contact between the needle and the tablet.
- Perform all gas handling in a ventilated enclosure.
- Do not reuse syringes between samples without purging.
9.0 Documentation:
Attach chromatograms, calibration curves, calculation sheets, and investigation reports to the final record.
10.0 Interpretation and Reporting:
Based on gas composition:
- High CO₂ → degradation due to moisture.
- O₂/N₂ presence → seal leakage or packaging defect.
- Other gases detected → further investigation needed.