Adjustment of Mobile Phase
Adjustment in composition of the mobile phase
Adjustment ph of the aqueous component of the mobile phase
Adjustment in concentration of salts in the buffer component of a mobile phase
Adjustment in composition of the mobile phase
- Minor compound of the mobile phase can be adjusted by +- 30 % Relative
- Change in any component cannot exceed +- 10 absolute
-Example of Binary mixture
– Example of temany mixture
-Example of Binary mixture
-
Eg 1: Ratio MP (80:20)
Minor solvent Ethanol
How much will be allowed adjustment EtOH ?
Calculated 30 % of 20
30*20/100=6
Identified which one is lower, either 30 % relative or +-10 absolute of minor component (EtOH)
30% of EtOH (6%) Is smaller than absolute 10 %
First component to give total 100%
MP composition Water: EtOH 86:14 with Relative -30 % EtOH change EtOH
MP composition Water : EtOH 74:26 with Relative + 30% EtOH change EtOH
Eg 2: Ratio MP (60:40)
Minor solvent Ethanol
How much will be allowed adjustment EtOH ?
Calculated 30 % of 40
30*40/100 = 12
Identified which one is lower, either 30 % relative or +-10 absolute of minor component (EtOH)
30% of EtOH (6%) Is More than absolute 10 %
First component to give total 100%
MP composition Water: EtOH 70:30 with Relative -30 % EtOH change EtOH
MP composition Water : EtOH 50:50 with Relative + 30% EtOH change EtOH
Termary Mixture
Ratio 70:25:5
EX:1 calculate 30 % variation for 2nd component
30*25/100 = 7.5
Identified which one is lower ether 30 % or +-10
30% 2nd component to give 7.5% is lower than absolute 10%
Use component to give a total 100 %
MP composition 77.5:17.5:5 with 2nd component -30% absolute change
MP composition 62.5:32.5:5 with 2nd component +30% absolute
EX:2 calculate 30 % variation for 3nd component
Ratio 70:25:5
30*5/100 = 1.5
Identified which one is lower ether 30 % or +-10
30% 3nd component to give 1.5 % is lower than absolute 10%
Use component to give a total 100 %
MP composition 71.5:25:3.5 with 2nd component -30% absolute change
MP composition 68.5:25:6.5 with 2nd component +30% absolute
PH adjustment in Mobile phase
+- 2 variation acceptable
Eg: Mobile phase ph 5.0
Taken ph 4.8 to 5.2
Adjustment of concentration of buffer +- 10 %
Eg buffer weight (KHPO4) is 20gm
Allow to 18g to 22 g