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)
 

 

 

 

 


 

 

 

 

 

 

 

 

 

When to ReValidate Your Methods?

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%

Gas Chromatography
EP recommendations
USP recommendations
Flow rate
±50%
±50%
Column length
±70%
±70%