Sodium Polyacrylate (2) (GSM-700 7E)
Sodium polyacrylate is a polymer whcih has weak ionic groups (carboxyl groups). The effect of eluent pH on GFC analysis of sodium polyacrylate is shown below :
Eluent of pH3------Dissociation of carboxyl groups is suppressed and mainly -COOH exists in the state of equilibrium. Therefore, the polymer is hydrophobic and adsorbed by the packing material and will not elute.
Eluent of pH7------In the low salt solution around 50mM, the polymer is partly dissociated and both -COO- and -COOH exist in the state of equilibrium. When -COOH is major, the adsorption mode with packing materials exists together with GFC mode. In this case, addition of organic solvents around 10 percent can remove adsorption mode and realize pure GFC mode.
Eluent of pH10-----Carboxyl groups are dissociated and mainly -COO- exists in the state of equilibrium. Therefore, the polymer is hydrophillic and recovery is very high. In this case, pure GFC mode can be realized without the addition of organic solvents.
As described in the avobe, the eluent pH is very important factor in the GFC analysis of weak ionic polymers.
GSM-700 7E is an old type of GF-7M HQ.
Sample : Sodium polyacrylate
Column : Shodex Asahipak GSM-700 7E (7.5mmID*250mm) Eluent : 50mM Phosphate buffer/CH3CN=90/10 Flow rate : 0.5mL/min Detector : Shodex RI Column temp. : Room temp.