Chemistry Reference
In-Depth Information
tAble 5.7
maximum specifications for Adjustments to lc operating conditions
parameter
maximum specification
comments
pH
±0.2 units
Buffer Salt
Concentration
±10%
Providing the pH variation is met
Ratio of Components in
the Mobile Phase
Components specified at 50% or
less: ±30% relative (to the total
mobile phase composition) or
±10% absolute
Change in any component cannot
exceed ±10% absolute;
adjustments can only be made to
one component in a ternary
mixture
a
UV Detector
Wavelength
No deviations
A validated procedure must be used
to verify that the error in the
detector wavelength setting is, at
most, ±3.0 nm
Column Length
±70%
Column Inner Diameter
LC
±50% (ORA)
For USP, see Reference 7
Adjust as long as linear velocity is
kept constant
Column Inner Diameter,
GC
±50%
Flow Rate (GC or LC)
±50%
See Section 5.8.2 for formula
Injection Volume
Reduced as far as consistent with
accepted precision and detection
limits
Particle Size
Reduced by as much as 50%
Column Temperature
±10°C
Column thermostating is
recommended to improve
reproducibility of t
r
GC Capillary Film
Thickness
−50% to 100%
Oven Temperature
Program (GC)
±20% (time)
a
Examples:
Binary mixtures:
For a specified ratio of 50:50; 30% is 15% absolute, exceeding limit of ±10% absolute of
any one component. Therefore, the mobile phase ratio may be adjusted only within the
range of 40:60 to 60:40. For a specified ratio of 2:98, 30% of 2 is 0.6% absolute. Therefore,
the maximum allowable adjustment is 1.4:98.6 or 2.6:97.4.
Ternary mixtures:
For a specified ratio of 60:35:5, 30% of the second component (35%) is 10.5% absolute,
exceeding maximum permitted ±10%; therefore, it may only be adjusted within the
range 25% to 45% absolute. For the third component, 30% of 5 is 1.5% absolute. In all
cases, a sufficient proportion of the first component should be used to give a total of
100%. Therefore, mixture ranges of 50:45:5 to 70:25:5 or 58.5:35:6.5 to 61.5:35:3.5
would meet the requirement.
