When to ReValidate Your Methods?
It is very common for analysts to have to adjust chromatography methods to meet performance criteria. But what changes are permitted while not having to revalidate the method?
We have tabulated the adjustments allowed by EP and USP, providing that system suitability parameters are achieved.
- LC:
Liquid Chromatography | EP recommendations | USP recommendations |
UV wavelength | No variation permitted | No variation permitted |
Flow rate | ±50% | ±50% More if ensuring linear velocity remains constant |
Column length | ±70% | ±70% |
Column I.D. | ±25% | May be adjusted provided linear velocity remains constant |
Particle size | No increases allowed Reduction to 50% | No increases allowed Reduction to 50% |
Column temperature | ±10 % Max 60°C | ±10 C |
Injection volume | May be decreased (assuming LOD and repeatability ok) | May be decreased (assuming LOD and repeatability ok) |
Mobile phase composition | Minor components ±30% relative or ±2% absolute whichever is larger | Minor components (<50%) ±30% relative or ±10% absolute whichever is the smaller |
pH | ±0.2 (±1% for neutral substances) | ±0.2 |
Conc. of salts in buffer | ±10% | ±10% |
- GC:
Gas Chromatography | EP recommendations | USP recommendations |
Flow rate | ±50% | ±50% |
Column length | ±70% | ±70% |
Column internal diameter | ±50% | ±50% |
Film thickness | -50 to 100% | -50 to 100% |
Particle size | -50%, no increase | Changes allowed SST must pass |
Column oven temperature | ±10 % | ±10 % |
May be decreased (assuming LOD and repeatability ok) | May be decreased (assuming LOD and repeatability ok) |
