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Stationary phase (SF) retention measurement

    The stationary phase retention after elution of a mobile phase is measured for two-phase solvent systems.  This can be measured in various ways but a straightforward method is by filling the rotor with a stationary  phase starting the centrifugation at 100 rpm and eluting the other or mobile phase at 2 ml/min or whatever flow is to be used.  The emergence of the mobile phase or solvent front is noted and measured.  After a few helium pressure into a graduate cylinder.  The retained stationary phase volume as the per cent of the total volume is calculated.  
    This is determined for the flow conditions: for the rotor filled with a stationary upper phase, the lower mobile phase is eluted (through the inner entry) in the T to H direction (L-i-T, CCW rotation of instrument), then the rotor filled again with the stationary phase centrifugation.  Next the rotor is filled with lower phase as the stationary phase and the upper phase is eluted in the other entry in the H to T direction(U-o-H), CCW and changing the centrifugation direction.  In this fashion, the stationary phase percent is measured for the solvent system.
    For the polar solvent systems, there is a low stationary phase retention with the other elution models of upper phase into the inner terminal and lower phase into other terminal. 

See Tables 1 and 2